-- Exactly 193 of 200 participants completing the study in each group (which, for a study administered in a community setting, is an essentially impossibly-high completion rate).
-- No author disclosures -- in fact, no information about the authors whatsoever, other than their names.
-- No information on exposures, lifestyles, or other factors which invariably influence infection rates.
-- Inappropriate statistical methods, which focus very heavily on p values.
-- Only 3 authors, which for a randomized controlled trial involving hundreds of people in different settings with regular follow-up, seems rather unlikely.
Also, look at the timings:
Received: 16-09-2025
Accepted: 29-09-2025
Available online: 14-10-2025
That's relatively fast but also the paper is not super in-depth.
And in general it seems like that the "International Journal of Medical and Pharmaceutical Research" is not quite well known.
See the Editors, not even pictures there: https://ijmpr.in/editorial-board/
> Incidence of ARIs was documented through monthly follow-up visits and self-reported symptom diaries validated by physician assessment.
This is basically impossible to accomplish for 386 participants who aren't in some form of captivity (e.g. incarcerated, institutionalized, in the military, or a boarding school). Nobody cares enough to maintain a "self-reported symptoms diary" and make monthly visits for some study. If they actually ran the study as designed, they would've have zero usable participants even starting from 400.
Saying nothing of the ethics of giving half the Vitamin D deficient patients presenting at your clinic with a placebo.
> (e.g. incarcerated, institutionalized, in the military, or a boarding school).
That's a pretty big list. Add Retirement communities and your pool increases even more. Add to that the fact that this is India where the population is at least 5x bigger and much more concentrated..
Most retirement communities don't have that much supervision.
Regardless, you can get a lot of data, but of it is from people who have other significant differences in lifestyle from the average person and so it is questionable how it applies. Military gets more physical fitness (we already know most of us need more). Boarding school implies young - children or just older, and so while not useful there are differences related to that to control for (military as well, unless you can get officers who are older thus allowing controlling for age).
> Most retirement communities don't have that much supervision
Retirement communities in India are relatively new. Most older folks get taken care of at home by domestic staff, which, given India's demographics, are incredibly cheap and thus plentiful.
There are retirement communities in India and end-of-life care centers as well. Societies change, and thanks to the internet, societies change faster than ever.
> It is: Negative, Unproductive, Antagonist, non Factual and frankly futile (unless provocative).
The comment gives clear reasoning and makes claims about the contents of the paper that are supported by reading the paper. To call it "non-factual" is simply incorrect. The word "futile" is nonsensical in this context.
You used three different words to complain that the comment critiques the study. There is nothing wrong with such critique in comments here, and indeed a healthy community requires that critique can rise to the top where it's warranted.
> Have you done an experiment lately to show counter proof? Beside claims what else do you have!
This is completely logically irrelevant, and suggests a fundamental misunderstanding of logic. Pointing out that a study is flawed does not require providing evidence for the opposite of the study's conclusion.
> This paper is very positive
A paper being "positive" has nothing whatsoever to do with whether its finding is correct, and it also has nothing whatsoever to do with whether its methodology is valid, and it also has nothing whatsoever to do with whether it accurately reports what was actually observed (i.e. whether any kind of fraud was involved).
> It is in fact (by personal experience)...
It is fundamentally impossible to know those things "by personal experience". That's why studies exist.
This was meant for Gwerbret (but he deleted the comment). Now is to whom may concern :)
Standing by your words you think this paper is shady and you are questioning the work and results behind it.
Moreover your comment somehow is on the very top it misleading the users or at least ridiculing the paper.
Answering to you: It is indeed very much connected to the LEVELS of Vit D not the absence of it. You fail to understand and acknowledge the importance of the results (even though you already know and confirm the benefits of Vit D).
Regulating the levels of it (keeping them higher then average) it prevents health issues by regulating many biological functions/pathways, raising the immunity and lifespan in general. This is the real cure which prevent incredibly terrible future health issues and suffering.
Edit: Just for this effort, this paper deserves Credit. Bravo.
> Just for this effort, this paper deserves Credit. Bravo.
I just went out and did a study myself. But I got 10,000 people, and 100% of the participants gave usable data, with a full record of every action taken, and every possible result. My study shows with 99.99% confidence that vit D is actually _bad_ for you. I hope you will congratulate my positive result (saving people from the dangerous effects of vit D !!) Or at the very least, congratulate me for my effort.
Obviously I completely fabricated that. Do you see how _claiming_ something doesn't mean it's true? Can you see the many red flags in my paragraph above? The other posters are pointing out similar red flags in the main article that's been shared.
I think the strongest criticism is just that being short of just about anything would cause significant effects. being short of water, calories, any vitamin, protein, etc.
Wanting to agree with a study’s conclusions and so ignoring its weaknesses and red flags is bad scientific practice, further reinforcing the comment questioning the value of this publication
Maybe you are right, on ignoring a study weaknesses and red flags is bad scientific practice.
Is that I have been involved personally so long in this topic, that I know for a fact that the results are Good. As I also know many good studies being ridiculed and buried on purpose. No one in the scientific community would dare to criticize a paper in that way. Constructive criticism is connected to intellectual, educated minds, all the rest deserves the same coin or being ignored.
I still don´t understand why that comment on top, (I have seen this to many times).
Vitamin D, red light therapy, insulin attenuating response of a walk, immunological benefit of allergen exposure, cognitive noise reduction and rest response of walks in forests.
While I find your comment enjoyably pithy, in the case of vitamin D, many humans are currently living at latitudes which they are not suited to (skin being too dark to generate enough vitamin D given the insolation), and eating diets which do not provide them with sufficient amounts of it (the carnivore diets of Inuits and similar groups being a good contrast).
Vitamin D supplementation in the UK - now there is a fascinating topic.
With the industrial revolution there was a problem of kids in cities getting rickets. This was due to a lack of vitamin C and that was due to a lack of daylight due to the smog.
The solution was to take the kids out of the city so they could spend time in the countryside.
However, along with the industrial revolution came steam trains, and, with steam trains, it became a lot easier to get fresh food from the farm to the city table.
Milk became an early commodity for this railway trade, in the days before refrigeration. Bottling had to be invented too, along with pasteurisation to get the modern milk product. They fortified it with vitamin D and, in time, made it mandatory in schools for kids to have dinky bottles of milk for their morning break. All kids hated the stuff but it was 'good for them' and good for keeping farmers gainfully employed.
Then the clean air acts came along, with the first street to ban fires in fireplaces being opposite the smoke free coal factory, the factory being anything but smoke free. Deindustrialisation happened too, so there were no cities with smokestack industries at their heart.
With clean air there was no longer any need to fortify the milk with vitamin D, so that stopped. From now on, kids would get their vitamin D doing things such as playing in the school playground.
But then we became seriously car dependent and the age of the free-range child was over. With 'stranger danger' and screens (initially just TV) taking over, we entered a new era of people not getting enough daylight again.
Along the way vitamin D has been downgraded, much like Pluto, from being a 'vitamin' to being a hormone. A lot of people want to point this out and explain the science to you. From hearing how some talk about vitamin D, it sounds like the recommended supplements are all over the place.
Clearly there are millions, if not billions that seem to be living just fine with not much sunlight in their lives and on no vitamin D supplements. Where's the rickets? Good question, but then, in Antarctica, where there are months of darkness to endure, they are on something like 20,000 units a day, and they probably know what they are doing.
Maybe following their example for this winter could be my next 'nutrition experiment'. Sometimes, when there is so much conflicting information, it is best to do an n=1 experiment with one's own body.
> Maybe following their example for this winter could be my next 'nutrition experiment'
Anecdotal and a sample size of 1, but I tried supplementing Vitamin D last year in the winter months. I live in the PNW, which between October and March, the sun is too low to trigger vitamin D synthesis in the skin to see if it had any effect on my energy levels and mood, I suffer from seasonal affective disorder pretty severely.
Taking 5,000 IU daily had no noticeable effect for me. A slight increase in energy levels but not significant enough that I'd be confident in attributing it to supplementation. I was hesitant to supplement more without medical advice and a blood test.
That's not to say Vitamin D isn't important (it is), and the scientists in Antartica definitely know what they're doing, but it's more to say YMMV.
For me, just making an effort to do more physical activity outdoors during the dark months had more of an impact
~5000 IU daily between February and May was barely enough to raise 25(OH) D level in my blood from 9 to 30 ng/ml.
Depending on who you ask, 30 is either the bound between "deficient" and "insufficient", or between "insufficient" and "sufficient". Regardless of who you ask, there's plenty of headroom until "excess".
Yes, it's possible but relatively hard to overdose on vitamin D, and due to a cock-up in some calculations in a study, until recently the recommended supplement amounts were about an order of magnitude too low: https://pmc.ncbi.nlm.nih.gov/articles/PMC5541280/
The NHS does recommend that everyone in the UK 'consider' vitamin D supplementation during the autumn and winter: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-... , because the amount of sunlight available in those months is not enough to maintain a healthy level.
It’s criminal that the US sent Somalian refuges to live in Minnesota. Those are some seriously brown people in the land of no vitamin D. Pretty big population in Seattle as well, which is worse due to cloud cover.
Not just cloud cover. Most areas in the PNW, the sun is so low in the sky between October and March that you can't synthesize vitamin D through the skin at all during those months, even on a bright sunny day.
Even during the summer up here, you really only get a window of roughly 10am to 3pm where enough UV-B rays can penetrate the atmosphere, in July. It's estimated that >80% of the PNW population are deficient (compared with 40% nationwide in the US).
That same podcast I mentioned pointed out that if a white person nude sunbathed in the winter in full sun, you’d get 2nd degree burns long before you made enough vitamin d.
The body stores it though. So how much of a deficit you’re running for how long matters.
It's only criminal if they aren't provided with the education/information they need to live healthy lives (which is possible with the right diet/supplements).
Dark skinned people do not produce enough vitamin D in northern latitudes because of melanin. If you’re black and in Minnesota you probably need supplementation.
Minnesota? Minnesota isn't particularly dark. Minneapolis is apparently on the same latitude as Venice, Italy, and I don't think of Venice as particularly dark or gloomy (to be fair, they probably have better weather).
But yeah. Low vitamin D levels are common even with lily white people in Northern Europe, and at least here in Norway everyone with dark skin knows that they need vitamin D supplements. Traditionally, public health recommendation (for everyone) was to take cod liver oil regularly for every month with an R in it.
I’m painfully aware of that being dark skinned myself. That doesn’t mean that Minnesota is inhospitable though (or that it would be criminal to send me there). It just means that they’d need to know that they need vitamin D supplements and perhaps regular blood screens. Idk if that happens though.
There are towns in Canada that have heated hallways that go between buildings so you can’t get completely snowed in during the winter. Maybe they should build those. Or the underground walkways they have in a couple of the cities.
I'm an Asian who was born and raised in a tropical weather region of my country. I'm now living in the PNW region of the US and it's always miserable from November-April. Vitamin D helps but it's not the same.
Seattle taught me a lot about procrastination. If you look outside and it’s sunny, and you promised yourself you’d go out today, drop whatever you’re doing and put on a jacket. Because by the time you finish it might be cloudy again. Seize the hour. There are no days to seize.
Doors are such an important invention that multiple unrelated animals have evolved modified body parts to serve as doors to burrows¹. Being able to store food is critically important for surviving low-food periods like winter without migrating. "Indoors" lets you store food without insects or other animals getting to it & stealing it. Fire allows for hardening clay, which lets you make a special tiny "indoors" called a "pot" for storing food. Also bricks so "indoors" can be made anywhere. With a roof the rain stays out & you can stay dry & warm, and not freeze at night. A significant portion of why fire is so important is it enables creating various sorts of "indoors".
> "Indoors" lets you store food without insects or other animals getting to it & stealing it.
This isn't true of human doors; insects are very small.
We've had the technology to keep things in wax-sealed clay jars for quite a while, but I'm not aware that this was done with grain, where preventing spoilage would have been most valuable. Granaries are open to the air. (And devote quite a lot of effort to slowing the spoilage of the grain.)
If you wanted food that wouldn't rot, instead of keeping it in an airtight environment, you dried it.
Every different food idem needs to be stored differently. There sometimes more than one option that will work, but you cannot treat everything the same.
If I have to survive the night, overhead protection and thermal insulation is more important than a fire. Source: I've tried using both without the other.
While I’d love to just go for a walk outside, the allergen exposure of the outdoors is too high most of the time. This elements any mental health benefits a walk in a forest might otherwise give.
I’m currently getting allergy shots. This is my 3rd attempt. Throughout my life I’ve gotten shots for about 12 years now. The last guy said they were better than I was kid and basically a cure now. 6 years later, and on the strongest dosage they’d give, getting 3 shots with each appointment… and I was never able to spend time outside without worry of what would follow.
There has been minor improvement in controlled testing, but no noticeable benefit when actually trying to live life. I go outside near nature once each year as a test to see if there was any progress. I can’t tolerate much more than that.
Shots work well for some. They worked decently well when I was a kid, but these days, not so much. I still hope the current ones will work, as I don’t have other options, but I’m beginning to lose hope.
Privileged commenter. Not everyone has access to a cell phone or the internet, so they can't respond to your statement. Not to mention some people have bad dyslexia or eyesight issues. We could play this game forever, and we'd all be dumber for it.
Walking in a forest is something that much of humanity can do, and it's not a particular privilege (in the pejorative modern sense) - even if there are a small number of people that have issues that would prevent this.
The issue I've found with these discussions is it appears there's mixed evidence on if vitamin D *supplementation* actually has a positive impact, regardless of vitamin D deficiency. In other words, is the deficiency causal or correlative.
I have no opinion on the matter, and am inclined to think there is at least some positive benefit. But YMMV
I took 10k iu via a multivitamin for a few months, and ended up with Vitamin D levels 5x higher than the maximum on the labcorp reference range. "Vitamin D toxicity"
It took many months to get the levels back to normal. Vitamin D is one of those things that once you overdose, it takes many months for the levels to slowly come down after you stop supplementing.
Be careful with Vitamin D!
The downside to having high levels is plaque/calcium deposits in arteries, if I'm not mistaken. Which can be mitigated by taking K2.
Are you aware of the history of setting acceptable levels of Vitamin D? Basically, 100 years ago, people experimented with cures for TB by giving patients one to two orders of magnitude higher dosage than the "vitamin D toxicity" levels reported today. Like insanely high numbers. Strangely enough, most people did recover from the TB, but they kept getting the treatments anyway, and that in a few instances led to bone issues. So for some reason that doesn't seem to be documented, they set the "safe level" of vitamin D to be something like two orders of magnitude lower than the level that actually caused issues. And that level has never been changed.
All of the studies I've seen around Vitamin D supplementation has shown that the "safe level" reported today is way, way lower than it should be. People appear to be just fine taking 10k IUs for months on end, even 7 years in one study. I think what we're learning is that the "safe level" is a very wide spectrum; some people could possibly be harmed from a low level, whereas some people are perfectly fine at a very high level.
And, fixed dosage never makes sense with Vitamin D. If you're supplementing, you need to make sure you regulate it based on sun exposure, since it's literally the Sun vitamin.
It's easy to double up if you decide to eat lunch outside because the weather is nice this month. I take 10k only if I'm indoors all day, and reduce or take none if I'm out.
> An excess of vitamin D causes abnormally high blood concentrations of calcium, which can cause overcalcification of soft tissues, including arteries and kidneys. Symptoms appear several months after excessive doses of vitamin D are administered. A mutation of the CYP24A1 gene can lead to a reduction in the degradation of vitamin D and thus to vitamin toxicity without high oral intake (see Vitamin D § Excess).
> Treatment
> In almost every case, ceasing vitamin D intake, combined with a low-calcium diet and corticosteroid drugs, will allow for a full recovery within a month. Bisphosphonate drugs (which inhibit bone resorption) can also be administered.[2]
Regardless, blood levels need to be checked for this sort of thing and doses are not one-size-fits-all. I also once was taking 10k daily, for several months, and ended up just barely in excess territory with no noticeable symptoms. (I settled on taking 4k daily in the long term.)
> In almost every case, ceasing vitamin D intake, combined with a low-calcium diet and corticosteroid drugs, will allow for a full recovery within a month.
Surprised to see just 4 weeks for a recovery. I got retested after 8 weeks (only minor improvement) and wasn't until 16 weeks until the test finally came back in range.
100% no dose is one-size-fits-all. I overdosed from taking a specialty multivitamin (it has a discord channel and everything). So was chatting with people taking the same vitamin, same dosages, also getting tested, but others had no issues at the same doses.
I guess I just absorb vitamin D with great efficiency, who knows.
Echo this with a PSA: it's a simple test to get your levels, and I'm a proponent of ensuring it's included when you have other regular blood tests (may have to ask for it). That can allow a person to see patterns, how effective any supplementation (and different amounts) are, etc.
I can use myself as an example: I have crohn's disease and I can take doses of 50000UI for some weeks, then 4000UI daily and after a year have my Vitamin D results as low as 20ng/ml.
The point wasn't the dose, I just picked a number out of my ass.
The point is that from that N IU the 100 people will absorb anything from 0-N, it's very individual and varied.
The only way to be sure is to test your levels, which costs money every time. There really should be a simple and cheap home test kit for it. You'd sell millions every year just in the Nordics and Canada =)
Maybe this comes across snide, but have you been to the Nordics? I can get tested at my GP for free practically as often as I'd like, I doubt you'd sell too much in the way of home test kits.
There is no way that's what they meant. 50k is an absurdly large dose that's way outside the safe intake range. 10k is used sometimes under medical supervision and even then it's a very short term measure. For long term intake, 4000IU is a widely accepted safe upper limit. 50k is an order of magnitude more than that.
There's plenty of documentation of people taking 50k for a period of time and having no side effects. There's been something like a dozen trials using high doses like this to treat TB, and they're usually successful, with no significant negative symptoms.
Conversely, some studies have shown that 4k IU does contribute to hypercalcemia in a small number of cases (4 per 1000). So actually 4k is deemed "not completely safe" as a limit.
The point is, the amount you take needs to be adjusted by a clinician, as the safe range for you is unknowable otherwise.
If your doctor is not seeing results they’ll keep upping the dose and I’ve heard of some that sound like an attempt at assisted suicide. Most of us would get toxicity from some of the ones I’ve heard.
My family is in this group. We are poor absorbers of vitamin D, some of my elder relatives need 5 times the "safe upper limit" to have healthy blood levels. As long as you're checking your blood values routinely (and for both D2 and D3, not just one or the other), it's reasonably safe. Sort of like other prescriptions in general.
I heard about a guy who ordered a bottle and ended up with vitamin D poisoning, on one of those Ira Glass style podcasts. Turns out they forgot to compound it before sending it out so he was getting “cask strength” vitamin D. Sounded very unpleasant.
Most of the vitamin D supplement studies have been very low quality in that they give all subjects in each group a fixed amount (or placebo). Ideally they should periodically test blood levels and titrate the dose to hit a target range. This would get us closer to establishing causality (or lack thereof) including a response curve. The amount needed to hit a given target will be wildly different for many individuals based on factors that are still not well understood.
Just my results (n=1) and I don't think this is exactly what you were saying, but just in case other read it the same way I did at first: having had (lab tested) vitamin D deficiencies, vitamin D supplementation can help to restore levels back into the desired range. So supplementation can have the desired effect of improving vitamin D levels (more below). It is a simple test that most doctors don't quibble about adding on to other blood tests (i.e. during annual checkup, for instance), but isn't generally checked by default. (note: insurers may want it to be "diagnostic" rather than "preventative" in order to cover the test.)
Whether it has a "positive impact" on overall health (which I believe to be your point), that would be even more anecdotal and also impossible for me to narrow down whether that one factor had any significant effect, so I won't posit that. And I agree that from different studies I've read, the actual science on it is pretty varied and I haven't seen anything conclusive. Even this study notes their conclusion was "... among adults with suboptimal baseline vitamin D levels".
This is solely my own anecdote, but I used to get bad seasonal depression every winter. I tried a number of interventions short of medication; none moved the needle very much. I started supplementing with vitamin D probably 8 years ago and haven't had any issues with seasonal depression since.
I'm pretty personally convinced that it was the supplements that helped here.
I was put on prescription vitamin D2 50000 IU and it caused a bunch of side effects for me including heart palpitations for over a week and then a paradoxical reaction to magnesium causing them to be even more intense.
Proceed with caution and listen to your body. Doctors were accusing every other thing than accepting whatever it did to my calcium / other electrolytes bothered my heart.
It's expensive in the US because one company has exclusive sales here (patent protection?), but you could try calcefidiol, weekly dose and is supposed to get levels up rapidly. Apparently it's the common form to take in Spain, and it's further down the metabolic pathway vs cholecalciferol. (I take but still have to get levels checked)
I took a blood test several weeks ago, my Vitamin D level was 14 ng/ml. I was so fatigued there were times I had to lay on my office floor because I didn't even have the energy to sit in my chair. I started taking 50k IU's weekly and then 10k IU's daily, and the results were dramatic. I went from having 0 energy to nearly normal. I also had soreness in my legs which went away.
Vitamin D isn’t technically a vitamin in the strict sense, because unlike the other vitamins the human body can produce it itself (by exposure to sunlight).
The body can also synthesize vitamin A from beta-carotene which is effectively two vitamin A molecules joined together (one rotated 180deg relative to the other).
Sure, many things are vitamins for one species but not another. (In fact, every vitamin must be able to be produced by at least one species – where else would it come from?)
Many animals can. There are a gene for it, humans don't have it. There is a lot of speculation as to why, but nothing really stands out (possibly just random chance - if you eat enough there is no advantage to keeping the gene and in turn no loss from losing it. However I'm unable to rule out other possibilities) https://pmc.ncbi.nlm.nih.gov/articles/PMC3145266/ is a really interesting survey of the issue across many different species.
From the article:
> Another argument supporting the suggestion that species which have lost their GLO gene were under no selective pressure to keep it, is that all species which have lost their GLO gene have very different diets but all of them have diets rich in vitamin C
What would a diet poor in vitamin C be considering that "everything else" makes it? I guess root vegetables? It feels like, if anything, this would imply a GLO gene decay more often than has happened, no?
That is probably a question for a nutritionist not me. My understanding is Grains, root vegetables, and meat are all low in vitamin C. Likely other things as well. But I'm not a nutritionist (I've read enough that I think I'm right here, but not enough to state it with confidence), so take the above with plenty of salt.
Most definitions of the word vitamin are not specific to humans. Wikipedia talks about "organisms", Britannica about "higher animal life", Webster about "most animals and some plants"
For most people just eating a good balanced diet and they are good to go. There are a few with genetic/biological issues and they need more - ask your doctor. Vitamin D is one that modern lifestyles likely don't get enough of and so probably worth it - again talk to your doctor.
If eating a "good balanced diet" were easy/normal, we'd have close to zero disease. Supplements are definitely a way to get as close as possible to balance when day to day food intake is chaotic.
there is no reason to think a good diet will prevent disease, nor that supplements will help in most cases. Good diet will prevent some disease, but disease is natural in the environment and good diet is mostly your immune system has what it needs to fight it off after you get it.
ErikCorry, bluGill and others like them get people killed with their exceedingly harmful assertions. It is pointless to argue with them since they're here to spread harm, also probably working for big pharma. The best that one can do is ask the reader to find the evidence for themselves.
Uncalled for. GP is pointing out that the fact the human body can produce Vitamin D means it is not a vitamin.
vi·ta·min
/ˈvīdəmən/
noun
any of a group of organic compounds which are essential for normal growth and nutrition and are required in small quantities in the diet because they cannot be synthesized by the body.
Glad to see this study, seems decent, but for a different perspective there was a relatively recent meta-analysis on the effectiveness of Vitamin D for RIs that suggested no effect:
One significant difference in this study is that it focused on people with low baseline vitamin D (10-30 ng/mL 25(OH)D), and moderate intervention (2000 IU daily).
The meta-analysis you posted did perform subgroup analysis on people with low baseline vitamin D (<25 ng/mL), but this included a wide range of intervention levels, 90% of which were <2000 IU daily equivalent. They also performed subgroup analysis on high intervention levels, but this included a wide range of baseline vitamin D, 90% of which were >25 ng/mL.
And also there's a difference between infection incidence, intensity, and duration, the evidence I've seen has been strongest in reducing intensity and duration. Also dosage might just be too low.
I've been feeling a little off lately with some respiratory symptoms and took 25,000 IU of Vitamin D, in people who are deficient (probably me lately) 400-1000 daily dose might not actually do enough to have an effect.
It's about time for a meta-meta analysis comparing the traits of the different sets of papers (N, dosage, deficiency status, time of year, duration/incidence/intensity, etc)
I live in Winnipeg, Manitoba where it is quite cold for a big majority of the year. I have dabbled with supplements because I get a couple of major colds every year.
I've heard things like you only need 15 minutes of sunshine per day to get your recommended dose of Vitamin D, but I've also heard it can be quite bad for you if you have too much in your system (and it's hard for your body to flush excess amounts).
If there a safe level of Vitamin D supplements where you won't run this risk? I don't drink milk either because I'm lactose intolerant.
"Winnipeg, Manitoba" ... "only need 15 minutes of sunshine per day to get your recommended dose of Vitamin D"
That doesn't apply to you most of the time, unfortunately. Vitamin D is the result of UVB exposure. For significant portions of the year, you don't get very much [1], compare with, say, [2] Orlando Florida in the US. 10-15 minutes is for a UV index of 7 [3], so that's only 4-6 months out of the year for you. And just based on my couple minutes with Google here, that number may also include the assumption that you're not just "out in the sun" for 15 minutes, but basically sunbathing. Lesser exposure may take longer: [4] Winter times can be effectively impossible because you can't sunbathe at 10 below (regardless of which scale I'm talking about) and you're not going to spend the requisite hours in the sun for what little skin is exposed. Or they can be outright impossible if your skin is dark enough.
But it does expose more skin, which [3] recommends!
Sadly, it doesn't say how long you should exposure yourself with a UV index of 1, which is what Winnipeg has today, and it's not even proper winter yet.
Yes, yes, you're an invincible winter god upon whom the temperature means nothing. Let us all acknowledge that and bow before you.
Now tell me everyone is doing that, all the time. I also live fairly north, which is part of why I've learned this about Vitamin D in my own research, and I can't help but notice that stores selling winter coats and gloves and other assorted cold gear don't go out of business ever year because nobody is buying them. Nor do I walk through a crowd of people in the middle of winter and have people point and laugh at me because I'm the only one in a coat.
Come on. You're just arguing to argue and swagger a bit, not because you actually think people are getting enough sun exposure in the middle of winter to get enough Vitamin D and there's nothing to worry about.
I'm not sure that people downvoting you have been around northerners much. Down here in the upper midwest US, we tend to consider 4 or 5C to be shorts weather in the spring. I've a friend who would wear flip flops / sandals outside down to roughly -10C.
Then again, most people aren't getting the equivalent of 15 minutes of index 7 UVB exposure at those temperatures, so it's not quite the same thing, but still.
People are downvoting because it has nothing to do with the comment they're replying to or the original post. Most people are well aware temperature is relative too, I live in the American South and there are certainly people here who will wear shorts in cold or freezing weather too.
I take 5000 IU per day year round and have not had any issues. Research suggests you can dose 10x that without major problems, although personally I wouldn't go higher than I am already.
To help prevent vitamin D toxicity, don't take more than 4,000 international units (IU) a day of vitamin D unless your healthcare professional tells you to. Most adults need only 600 IU of vitamin D a dayhttps://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...
Part of the issue with vitamin supplements is that the bioavailability can be unpredictable. The actual amount absorbed can vary between 10% and 100% depending on the time of day, supplement formulation, what foods if any are taken together, as well as the particular characteristics of the individual's intestines, which are difficult to assess. Because supplements are not regulated as pharmaceuticals in the United States, this variability can be severe; in the worst cases, supplements do not even contain the active principle.
So, I am not surprised that someone needs to take 5000 IU to get 600 IU worth of effect. Institutional medical authorities are (rationally) quite defensive when cautioning readers about supplement consumption; they must consider the worst case (100% bioavailability) when assessing the risk of overdose.
As an alternative to vitamin supplements, exposing common dietary mushrooms to ultraviolet light converts (by an uncatalysed photochemical reaction) the ergosterol therein to calciferol. How best to achieve this in a home setting is unclear.
One number is not going to work for everyone. The only way to be sure is to get a blood test for Vitamin D levels. I get tested with my yearly physical, but if someone really cares they can get more frequent blood tests.
As has been commented elsewhere, everyone absorbs vitamin D differently, this really is a matter where someone should just get tested, if they (and their doctor) decide supplementation is needed, do so, test again, and adjust dosage accordingly until desired levels are attained.
Not medical advice here, but harmful effects from vitamin D exposure/toxicity generally only happen at very high levels, or if high doses are taken over long periods of time (as excess can be stored in fatty tissue/liver). Doctors often prescribe a very high dose (like 50,000 IUs) for individuals who are very deficient (often taken once a week, not daily) for a short period before going on a more standard (400-2,000, maybe 5,000) IU dose for maintenance.
The advice on this is all over the map and that's a big problem in the space. Reputable medical sources have recommendations almost two orders of magnitude off from each other at times.
...cites several cases where daily supplementation of 50K IU was required to restore normal D levels, although also a case where that same dose caused toxicity. As one of the other commenters in the thread noted, working with your doctor to establish the right level is probably the right move. If nothing else, they have the capability to test your serum levels to see where you're at.
I experimented with taking 10,000 IU a day for about a year. I had my D levels checked with my normal yearly blood test (lipids, etc) and it put me into the high normal range. I still take 5000 IU daily and have for years with no ill effects.
I should note that I live in a place that sees little sun for five or so months a year.
You can't possibly have the same recommendation for all geographies. Florida and Scotland have somewhat different level of UVB especially throughout the winter, come on.
Vitamin D toxicity is a legitimate concern, so those dosing should be mindful of it, depending on dosage and existing serum levels. Don't action on medical advice from strangers on the internet alone, talk to you doctor or other credentialed medical practitioner you work with if needed.
You probably have to really try to take too much Vitamin D with any over the counter supplement (<=5,000 IU), especially if you live that far north. For reference, a prescription dose for someone who is low is usually 50,000 daily.
It should be part of your standard blood tests so you should know if you're running high or low and your doctor can recommend or prescribe a good dose.
With 5,000 IU sometimes taking several at a time I had blood levels of Vitamin D at the top of the range which wasn't dangerous it was just informative, "hey you're having enough, tone it down".
First know that the body will stop making vitamin D before you reach overdose quantities. This means you should take vitamin D in the morning.m rather than the evening. Second know that vitamin D is fat soluble. So if you are losing weight, you can more easily overdose if you have high levels stored in your fat. Also know the body won’t absorb as much vitamin D if you don’t take it with fat.
This can make dosing tricky. You can be taking an amount that is safe right now, but then is too much later.
You can max out your body’s vitamin D production even on a cloudy day, though the sun’s angle of incidence effects production.
The body typically maxes production at something like 20k iu (pleae verify this number it has been a while since I learned it), so staying below this number should mostly safe.
The USDA has set its recommended daily allowance mostly to avoid rickets. It is largely considered too low a number for general well being.
I live in north western Washington, and previously used to combat seasonal affective disorder, with some pretty dark thoughts come february. Since I started taking 1k D3 some 20 years ago much of the seasonal mental health has gone away. I take 2k D3 consistently currently, and if I run out for more than a week my mood starts to deteriorate quickly. I still haven’t proved causation since there are likely reasons I’ve let myself run out of the supplement that long, but it is so consistent that I treat it as causal at this point. YMMV
Please do research above just asking a forum for dosing advice though. This is a well educated place, and I would very much trust it as a starting point, but there is a lot of good published content on the topic. Though, I admit google is so bad today, I might fail to find any of the content I referenced years ago… if you use chatgpt make sure to require references, and check them. I find that using multiple instances to review research references separately prevents some context based poisoning as well. And pointing out inconsistencies can be a good way to find nuance in a topic. Though sometimes LLM will just waffle, and the context may be done
I've heard the 15 minutes is all you need. I've also heard that in winter the sun is so weak that no amount of sunshine gives you any. (even if you were naked outside in winter - risking frostbite).
I'm not a medical doctor. I cannot evaluate any of the above claims. I wish I could find a source I could trust.
Depends on where you are. Latitudes above roughly 35 degrees N, the sun is too low in the sky roughly between October and March to allow for UV-B rays to penetrate, which is what your skin needs to synthesize vitamin D.
So yes, if you live in the northern regions, you don't produce any at all from sun exposure, even on a bright sunny day, during most of the year.
Up here in the PNW, even in the summer, you only have a window of roughly 4 to 5 hours where the sun is high enough, in July.
I've heard things like you only need 15 minutes of sunshine per day to get your recommended dose of Vitamin D
The figure I read years ago was that it takes 15 minutes in short sleeves to get the necessary light exposure at the 45th parallel in winter. I'm right at the 45th parallel and I don't go out in short sleeves in the winter, so I imagine it's significantly worse for you!
You don't need to guess, go to your GP and get yourself tested. It's not expensive, depending on where you're from it might even be free, and usually you get the results back already the next day.
Generally agree, but unlike water-soluable vitamins, vitamin D can store excess in fatty tissue and the liver, and so if a person takes a large dose (generally 10,000 IU daily or more), they could develop toxicity over time due to the build-up. That's why it's important to test and adjust dosages according to the data.
I take 8000 D3 (+200ug K2 MK7) daily and I'm fine. since covid I go like this for entirety of winter and then back down when summer comes. Perhaps you live in a climate where you get a lot of sun exposure and somehow overdosed on that. A guy from vitadmindwiki.com even says that you'd have to take 14000IU daily for a year until reaching toxicity limit (although this guy tends to sometimes say different things on the same topic, so I'd be cautious on whether this is the exact amount)
https://vitamindwiki.com/Overview+Toxicity+of+vitamin+D
Although it'd be great if you explained what exactly happened, perhaps it wasn't a result of taking vitamin D itself but rather some external thing. Judging by "painful experience" I assume kidney stones, which could be caused by too much calcium or genetic preference. not a doctor or an expert on the topic though, just open for a discussion :)
The symptoms are hard to describe (but did not include kidney stones), but it was obvious that something was drastically wrong and the drastic wrongness went away in response to my completely avoiding all sunlight and dietary sources of vitamin D and my doing a few other things described below.
Most people could probably take as much supplemental vitamin D as I did without incurring this adverse effect, but there is no straightforward way for a person to know whether they are in the minority of people who will incur the effect. (I do remember that having Northern European ancestry makes the effect more likely.)
The drastic wrongness started showing up after only a few months of whatever high dose of D I was taking (and I regret that I cannot provide this information: I did search for it briefly; but it was definitely not an "absurd amount") so if you've been taking the 8000 D3 for years, then the drastic wrongness is unlikely to suddenly show up in your case -- and if it does show up it would probably be because you contracted some sort of chronic infection.
The presence of certain kinds of chronic infections and genetics are the main causative factors according to the information I relied on 25 years ago. Actually, here is the basic information. I followed most aspects of the protocol including my obtaining a prescription for olmesartan, but then I lost interest when the drastic wrongness went away (after not much longer than 4 months IIRC). I was also probably on an antibiotic during this recovery.
P.S., I take as much MK7 as you do (i.e., twice as much as the "suggested usage" on the label) and have for many years, just without supplemental vitamin D.
Most interesting, will bear that in mind. To this date I haven't encountered any "drastically wrong" symptoms with my d3 usage and frankly haven't heard that much about any adverse events linked to vitamin d3. If you feel comfortable with that then you could disclose what exactly is that adverse effect you've been experiencing, but I see that you try to avoid this topic so no pressure :)
It's not that I'm unwilling to publish the information: it is just that I despair of putting into words how I knew something was drastically wrong with my physiology -- especially now that 25 years have gone by.
A few other interesting links with Vitamin D absorption. Surprised nobody has brought up gut dysbiosis and the role microbiome plays in Vitamin absorption. I'm finding it increasingly difficult to discern whether the things we consume are for the direct benefit of our cells and metabolic needs or via a more indirect path if the things we consume directly affect the microbiome within us which then translates into either nourishment or inflammation within us. Since microbiomes can change rapidly in composition, this feels like a game of nurturing over the long-haul with some minor blips along the way.
[1] "connection between vitamin D and the immune system through gut bacteria and may have applications for improving cancer therapies"
[2] "How the Gut Microbiome Affects Vitamin D Absorption"
[3] "vitamin D may affect the host-microbiota relationship."
I take 10k IU of vitamin D if I feel a cold coming on. I used to get extremely bad colds very frequently, and every time I get frustrated and read whatever research might be helpful. A year ago I came across some info about LL-37, and found that vitamin D might help, and that's when I started taking it. https://pmc.ncbi.nlm.nih.gov/articles/PMC9134243/
The big dose of D seems to help. I'm certain I'm deficient, since I already take 2-4k daily, which noticeably helpsy winter blues. It's the first time I can "arrest" a cold, and even if I get sick the symptoms aren't nearly as bad.
My full protocol for if I start feeling a cold is this:
1. 10k vitamin D
2. Stay extremely warm when I sleep. Uncomfortably warm.
3. Butyrate (probably a placebo)
4. Curcumin (almost certainly a placebo).
Because I always forget lol. My point is that I still had a good effect even though I'm doing an extremely sub-optimal job of taking it/probably getting a dose-equivalence of way less than 2k IU/day.
Unfortunately this is a common error people make, many vitamins and other supplements are absorbed better when taken with food, even if that seems counterintuitive at first.
It really depends. Other things like iron is best taken fasted (and paired with Vitamin C). Coffee also blocks iron absorption, so many people supplement at nighttime. Also things like Zinc and Copper both compete with each other for absorption, so best to avoid taking them at the same time.
If you're optimizing your supplement stack, really gotta research each one individually (and how each impact the absorption of the others)
In the US it is very easy to test your vitamin D levels. I recently had mine done and was just below normal range. Started supplementing and will test again in 6 months.
A lot of people are critiquing the statistical methods and quality of the study, which is fine. But it's worth pointing out that you—the individual—should not be concerned with someone else's p-value. You should be concerned with maximizing your own utility. A safe, possibly effective, and cheap intervention is probably worth trying. If it was more expensive or less safe, it would require more evidence to try.
Take it from an academic like me that peer review in just over a month is rare and a sign of low-quality editorial work at the journal (the exceptions would be the most open, progressive journals like PCI and similar).
The formatting/style and peer review history alone are enough for me to doubt this. Of course, the other users' points about study design and lack of transparency make it even harder to trust the claims.
Do we really know what "optimal" vitamin D levels are? I've heard a wide range of answers on this, and it's not even clear to me that we know whether there is natural human variability in the amount needed.
I haven't seen convincing evidence that vitamin D supplementation is materially useful for anything but rickets. I get the impression that naturally high serum levels are an effect rather than a cause of other positive things, and that supplementation mostly increases serum levels without effecting positive things. It doesn't seem harmful either, so can't hurt might help?
What about the article that that talks about Vitamin D being the same chemical as rat poison and that the positive effects it has on our bodies may be due to the fact that we are low-level poisoning ourselves with it?
"Vitamin D3, also known as cholecalciferol, is used as a rodenticide because it is highly toxic to rodents when ingested in sufficient quantities.
It functions by causing a life-threatening elevation in blood calcium and phosphorus levels, leading to severe acute kidney failure"
"Despite its use in rodenticides, vitamin D3 is safe for humans and pets when consumed in normal dietary or supplement doses.
However, extremely high doses of vitamin D3 can be toxic to humans as well, potentially leading to hypercalcemia, kidney stones, and renal failure.
The difference in susceptibility between rodents and humans is significant; rodents are much more sensitive to the effects of cholecalciferol, which is why it is effective as a rodenticide."
The theory is that we are just poisoning ourselves by taking it and that our bodies react to being poisoned with the positive effects that are well documented and observed.
Reminder that the Recommended Daily Allowance of Vitamin D found on all the labels (800 IU) is mistakenly too low, by a factor of 10x, due to a maths error (should be 8000 IU). It has not been corrected yet. Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC5541280/
Supplementing with vitamin D is honestly one of the easiest things you can do... it's cheap, available everywhere, and makes a real difference. Just make sure you're also taking magnesium citrate (or another good form of magnesium) with it, since your body needs magnesium to properly use vit D
An even better option is to go to your GP and have them run your bloodwork. It's cheap, depending on where you're from it might even be free, and you don't have to guess or randomly pick supplements you read about online. Most people on HN will live to a very high age, there's no reason to take random gambles on what you do to your body.
Can confirm anecdotally. I used to get 2-3 colds a year for about 15 years straight, especially during season changes when the humidity levels changed. Started taking 5000 IU vitamin D3 daily about 2 years ago and I haven't gotten sick since.
There were a few soft recommendations. Specifically I remember an ER doctor in 2019 saying vitamin D seemed to be a differentiator in the sample of cases he was seeing in the ER (everyone was starting to panic) and the CDC walking it back as unsubstantiated. I mentioned it at work, then 10 days later my boss's boss asked me where I had heard it, because he had heard the same thing.
There have been a number of people on HN who have attributed any measurable COVID benefit of Vitamin D, to a confounding variable, as recently as 3 months ago - https://news.ycombinator.com/item?id=44705486 The Big Vitamin D Mistake
One of the best treatments is interferon. It's something you will also produce yourself, with therapeutic effect, if exposited to sunlight or the infrared light used in red light therapy. Here's a video about it, from a continuing education provider: https://www.youtube.com/watch?v=oRkxH56LqCo
Heliotherapy is well-due for a resurgence. One of my favourite youtubers (conquer aging or die trying) has a great interview with a medical doctor about sunlight as a medical intervention. Well worth the watch:
Yeah, this is a crucial point. This is studying "adults with suboptimal baseline." If you have a vitamin deficiency and get sick, I would expect supplementation with that vitamin to provide some relief, regardless of which vitamin it is.
This does not mean that the same will happen for people who did not have a deficiency.
Having said that, there is good evidence that Vitamin D deficiency is widespread, and supplementation of Vitamin D is relatively safe unless you take excessive amounts.
It is my general understanding that unless you are severely deficient, Vitamin D supplementation generally takes weeks to bring levels up. It's unlikely that taking it for a few days is going to have any measurable impact on your recovery from illness unless you are severely deficient and/or taking MASSIVE doses, which may or may not be recommended depending on your prior levels and BMI.
Unfortunately Vitamin D deficiency tests (probably it is not covered by your insurance), high dose supplements are currently pushed so much by Doctors I started to think this is almost a scam. Most of the research about the subject are very noisy and conflicting.
If there is any reason for the test, it would be diagnostic and not preventative, and that is generally covered. Just checking cause you want to know your levels generally wouldn't be, but there are any number of symptoms that could be related to that.
As for it being a "scam" - there are enough valid studies that show what this one did, that folks who are deficient that are able to raise their levels tend to be slightly healthier.
There isn't necessarily evidence for supplementation beyond "normal" range, and I do agree that no one should just take high-dose vitamin D supplements without data (tests) that it is necessary.
I'm sure people who supplement or have good D levels also take care of themselves, generally - because they know D is one of the supplements that make a difference both somatic and psychological.
Heh...this is a shady study if I ever saw one.
-- Exactly 400 study participants recruited.
-- Exactly 193 of 200 participants completing the study in each group (which, for a study administered in a community setting, is an essentially impossibly-high completion rate).
-- No author disclosures -- in fact, no information about the authors whatsoever, other than their names.
-- No information on exposures, lifestyles, or other factors which invariably influence infection rates.
-- Inappropriate statistical methods, which focus very heavily on p values.
-- Only 3 authors, which for a randomized controlled trial involving hundreds of people in different settings with regular follow-up, seems rather unlikely.
In the PDF they are all titled as
"Assistant Professor, Department of General Medicine, Arundathi Institute of Medical Sciences, Dundigal, Medchal Malkajgiri, Telangana, India"
The 2nd author is listed here: https://aims.ac.in/general-medicine/ I did not find any trace for the other two authors (do they exist?).
Also, look at the timings: Received: 16-09-2025 Accepted: 29-09-2025 Available online: 14-10-2025
That's relatively fast but also the paper is not super in-depth.
And in general it seems like that the "International Journal of Medical and Pharmaceutical Research" is not quite well known. See the Editors, not even pictures there: https://ijmpr.in/editorial-board/
The first author is probably him: Dr. G Naresh (Asst. Prof.)
https://aims.ac.in/general-medicine/
My bullshit meter redlined as well.
> Incidence of ARIs was documented through monthly follow-up visits and self-reported symptom diaries validated by physician assessment.
This is basically impossible to accomplish for 386 participants who aren't in some form of captivity (e.g. incarcerated, institutionalized, in the military, or a boarding school). Nobody cares enough to maintain a "self-reported symptoms diary" and make monthly visits for some study. If they actually ran the study as designed, they would've have zero usable participants even starting from 400.
Saying nothing of the ethics of giving half the Vitamin D deficient patients presenting at your clinic with a placebo.
> (e.g. incarcerated, institutionalized, in the military, or a boarding school).
That's a pretty big list. Add Retirement communities and your pool increases even more. Add to that the fact that this is India where the population is at least 5x bigger and much more concentrated..
Most retirement communities don't have that much supervision.
Regardless, you can get a lot of data, but of it is from people who have other significant differences in lifestyle from the average person and so it is questionable how it applies. Military gets more physical fitness (we already know most of us need more). Boarding school implies young - children or just older, and so while not useful there are differences related to that to control for (military as well, unless you can get officers who are older thus allowing controlling for age).
> Most retirement communities don't have that much supervision
Retirement communities in India are relatively new. Most older folks get taken care of at home by domestic staff, which, given India's demographics, are incredibly cheap and thus plentiful.
I forgot this was India, my mistake. Though that means there are essentially no retirement communities to work with there.
There are retirement communities in India and end-of-life care centers as well. Societies change, and thanks to the internet, societies change faster than ever.
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> It is: Negative, Unproductive, Antagonist, non Factual and frankly futile (unless provocative).
The comment gives clear reasoning and makes claims about the contents of the paper that are supported by reading the paper. To call it "non-factual" is simply incorrect. The word "futile" is nonsensical in this context.
You used three different words to complain that the comment critiques the study. There is nothing wrong with such critique in comments here, and indeed a healthy community requires that critique can rise to the top where it's warranted.
> Have you done an experiment lately to show counter proof? Beside claims what else do you have!
This is completely logically irrelevant, and suggests a fundamental misunderstanding of logic. Pointing out that a study is flawed does not require providing evidence for the opposite of the study's conclusion.
> This paper is very positive
A paper being "positive" has nothing whatsoever to do with whether its finding is correct, and it also has nothing whatsoever to do with whether its methodology is valid, and it also has nothing whatsoever to do with whether it accurately reports what was actually observed (i.e. whether any kind of fraud was involved).
> It is in fact (by personal experience)...
It is fundamentally impossible to know those things "by personal experience". That's why studies exist.
> It is in fact (by personal experience) essential for the health
You might be right, but this study doesn't show that because it's a genuinely bad study. Someone serious should do a real study on it.
This was meant for Gwerbret (but he deleted the comment). Now is to whom may concern :) Standing by your words you think this paper is shady and you are questioning the work and results behind it. Moreover your comment somehow is on the very top it misleading the users or at least ridiculing the paper. Answering to you: It is indeed very much connected to the LEVELS of Vit D not the absence of it. You fail to understand and acknowledge the importance of the results (even though you already know and confirm the benefits of Vit D). Regulating the levels of it (keeping them higher then average) it prevents health issues by regulating many biological functions/pathways, raising the immunity and lifespan in general. This is the real cure which prevent incredibly terrible future health issues and suffering.
Edit: Just for this effort, this paper deserves Credit. Bravo.
> Just for this effort, this paper deserves Credit. Bravo.
I just went out and did a study myself. But I got 10,000 people, and 100% of the participants gave usable data, with a full record of every action taken, and every possible result. My study shows with 99.99% confidence that vit D is actually _bad_ for you. I hope you will congratulate my positive result (saving people from the dangerous effects of vit D !!) Or at the very least, congratulate me for my effort.
Obviously I completely fabricated that. Do you see how _claiming_ something doesn't mean it's true? Can you see the many red flags in my paragraph above? The other posters are pointing out similar red flags in the main article that's been shared.
I think the strongest criticism is just that being short of just about anything would cause significant effects. being short of water, calories, any vitamin, protein, etc.
Wanting to agree with a study’s conclusions and so ignoring its weaknesses and red flags is bad scientific practice, further reinforcing the comment questioning the value of this publication
Maybe you are right, on ignoring a study weaknesses and red flags is bad scientific practice. Is that I have been involved personally so long in this topic, that I know for a fact that the results are Good. As I also know many good studies being ridiculed and buried on purpose. No one in the scientific community would dare to criticize a paper in that way. Constructive criticism is connected to intellectual, educated minds, all the rest deserves the same coin or being ignored. I still don´t understand why that comment on top, (I have seen this to many times).
Vitamin D, red light therapy, insulin attenuating response of a walk, immunological benefit of allergen exposure, cognitive noise reduction and rest response of walks in forests.
Man keeps trying to bring the outdoors inside.
While I find your comment enjoyably pithy, in the case of vitamin D, many humans are currently living at latitudes which they are not suited to (skin being too dark to generate enough vitamin D given the insolation), and eating diets which do not provide them with sufficient amounts of it (the carnivore diets of Inuits and similar groups being a good contrast).
Amusing how thanks to the war on cholesterol the UK unravelled a lot of egg eating habits - a natural source of vitamin D.
The UK also consumed a lot more liver than it does today I imagine...
Vitamin D supplementation in the UK - now there is a fascinating topic.
With the industrial revolution there was a problem of kids in cities getting rickets. This was due to a lack of vitamin C and that was due to a lack of daylight due to the smog.
The solution was to take the kids out of the city so they could spend time in the countryside.
However, along with the industrial revolution came steam trains, and, with steam trains, it became a lot easier to get fresh food from the farm to the city table.
Milk became an early commodity for this railway trade, in the days before refrigeration. Bottling had to be invented too, along with pasteurisation to get the modern milk product. They fortified it with vitamin D and, in time, made it mandatory in schools for kids to have dinky bottles of milk for their morning break. All kids hated the stuff but it was 'good for them' and good for keeping farmers gainfully employed.
Then the clean air acts came along, with the first street to ban fires in fireplaces being opposite the smoke free coal factory, the factory being anything but smoke free. Deindustrialisation happened too, so there were no cities with smokestack industries at their heart.
With clean air there was no longer any need to fortify the milk with vitamin D, so that stopped. From now on, kids would get their vitamin D doing things such as playing in the school playground.
But then we became seriously car dependent and the age of the free-range child was over. With 'stranger danger' and screens (initially just TV) taking over, we entered a new era of people not getting enough daylight again.
Along the way vitamin D has been downgraded, much like Pluto, from being a 'vitamin' to being a hormone. A lot of people want to point this out and explain the science to you. From hearing how some talk about vitamin D, it sounds like the recommended supplements are all over the place.
Clearly there are millions, if not billions that seem to be living just fine with not much sunlight in their lives and on no vitamin D supplements. Where's the rickets? Good question, but then, in Antarctica, where there are months of darkness to endure, they are on something like 20,000 units a day, and they probably know what they are doing.
Maybe following their example for this winter could be my next 'nutrition experiment'. Sometimes, when there is so much conflicting information, it is best to do an n=1 experiment with one's own body.
> Maybe following their example for this winter could be my next 'nutrition experiment'
Anecdotal and a sample size of 1, but I tried supplementing Vitamin D last year in the winter months. I live in the PNW, which between October and March, the sun is too low to trigger vitamin D synthesis in the skin to see if it had any effect on my energy levels and mood, I suffer from seasonal affective disorder pretty severely.
Taking 5,000 IU daily had no noticeable effect for me. A slight increase in energy levels but not significant enough that I'd be confident in attributing it to supplementation. I was hesitant to supplement more without medical advice and a blood test.
That's not to say Vitamin D isn't important (it is), and the scientists in Antartica definitely know what they're doing, but it's more to say YMMV.
For me, just making an effort to do more physical activity outdoors during the dark months had more of an impact
~5000 IU daily between February and May was barely enough to raise 25(OH) D level in my blood from 9 to 30 ng/ml.
Depending on who you ask, 30 is either the bound between "deficient" and "insufficient", or between "insufficient" and "sufficient". Regardless of who you ask, there's plenty of headroom until "excess".
Yes, it's possible but relatively hard to overdose on vitamin D, and due to a cock-up in some calculations in a study, until recently the recommended supplement amounts were about an order of magnitude too low: https://pmc.ncbi.nlm.nih.gov/articles/PMC5541280/
The NHS does recommend that everyone in the UK 'consider' vitamin D supplementation during the autumn and winter: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-... , because the amount of sunlight available in those months is not enough to maintain a healthy level.
I don't think vit c has anything to do with daylight/smog. vit d, definitely (and so not rickets).
> This was due to a lack of vitamin C and that was due to a lack of daylight
I think you also meant Vitamin D there
Are they that unpopular? Seem like a staple of an English Breakfast.
Couldn't quickly find any sources for the UK specifically but this should suffice
https://pmc.ncbi.nlm.nih.gov/articles/PMC4632449/
It’s criminal that the US sent Somalian refuges to live in Minnesota. Those are some seriously brown people in the land of no vitamin D. Pretty big population in Seattle as well, which is worse due to cloud cover.
> which is worse due to cloud cover.
Not just cloud cover. Most areas in the PNW, the sun is so low in the sky between October and March that you can't synthesize vitamin D through the skin at all during those months, even on a bright sunny day.
Even during the summer up here, you really only get a window of roughly 10am to 3pm where enough UV-B rays can penetrate the atmosphere, in July. It's estimated that >80% of the PNW population are deficient (compared with 40% nationwide in the US).
That same podcast I mentioned pointed out that if a white person nude sunbathed in the winter in full sun, you’d get 2nd degree burns long before you made enough vitamin d.
The body stores it though. So how much of a deficit you’re running for how long matters.
Minnesota, not Wisconsin. Same latitude and a fair point.
I knew it was Minnesota, not sure why I wrote WI.
It's only criminal if they aren't provided with the education/information they need to live healthy lives (which is possible with the right diet/supplements).
Dark skinned people do not produce enough vitamin D in northern latitudes because of melanin. If you’re black and in Minnesota you probably need supplementation.
Minnesota? Minnesota isn't particularly dark. Minneapolis is apparently on the same latitude as Venice, Italy, and I don't think of Venice as particularly dark or gloomy (to be fair, they probably have better weather).
But yeah. Low vitamin D levels are common even with lily white people in Northern Europe, and at least here in Norway everyone with dark skin knows that they need vitamin D supplements. Traditionally, public health recommendation (for everyone) was to take cod liver oil regularly for every month with an R in it.
To your eyes. But the sun angle chews up the wavelengths that make vitamin D.
I’m painfully aware of that being dark skinned myself. That doesn’t mean that Minnesota is inhospitable though (or that it would be criminal to send me there). It just means that they’d need to know that they need vitamin D supplements and perhaps regular blood screens. Idk if that happens though.
They have all already disappeared form public and it's only in the 40s right now. By winter you would swear no Somalis live in MN.
There are towns in Canada that have heated hallways that go between buildings so you can’t get completely snowed in during the winter. Maybe they should build those. Or the underground walkways they have in a couple of the cities.
It was never about doing right for people, it was about making unbelievable gobs of money using them as pawns.
I mean I guess they could have dumped them in West Virginia or Kentucky and that would have been much much worse.
I'm an Asian who was born and raised in a tropical weather region of my country. I'm now living in the PNW region of the US and it's always miserable from November-April. Vitamin D helps but it's not the same.
Seattle taught me a lot about procrastination. If you look outside and it’s sunny, and you promised yourself you’d go out today, drop whatever you’re doing and put on a jacket. Because by the time you finish it might be cloudy again. Seize the hour. There are no days to seize.
Man suffered outdoors very much, for a million years.
Man want both good of indoors and good of out outdoors.
Indoors best invention since fire.
Doors are such an important invention that multiple unrelated animals have evolved modified body parts to serve as doors to burrows¹. Being able to store food is critically important for surviving low-food periods like winter without migrating. "Indoors" lets you store food without insects or other animals getting to it & stealing it. Fire allows for hardening clay, which lets you make a special tiny "indoors" called a "pot" for storing food. Also bricks so "indoors" can be made anywhere. With a roof the rain stays out & you can stay dry & warm, and not freeze at night. A significant portion of why fire is so important is it enables creating various sorts of "indoors".
¹https://en.wikipedia.org/wiki/Phragmosis
> "Indoors" lets you store food without insects or other animals getting to it & stealing it.
This isn't true of human doors; insects are very small.
We've had the technology to keep things in wax-sealed clay jars for quite a while, but I'm not aware that this was done with grain, where preventing spoilage would have been most valuable. Granaries are open to the air. (And devote quite a lot of effort to slowing the spoilage of the grain.)
If you wanted food that wouldn't rot, instead of keeping it in an airtight environment, you dried it.
Every different food idem needs to be stored differently. There sometimes more than one option that will work, but you cannot treat everything the same.
Dried food requires indoor storage.
Maybe better.
If I have to survive the night, overhead protection and thermal insulation is more important than a fire. Source: I've tried using both without the other.
There's definitely a reason we use tents while camping and don't just huddle around the fire.
Chimney next best invention.
Man love synergy.
You not from tribe.
Fire indoors but smoke outdoors.
<grunt>
Man agree
Few words good
fewer gooder
While I’d love to just go for a walk outside, the allergen exposure of the outdoors is too high most of the time. This elements any mental health benefits a walk in a forest might otherwise give.
Allergy shots work very well.
I’m currently getting allergy shots. This is my 3rd attempt. Throughout my life I’ve gotten shots for about 12 years now. The last guy said they were better than I was kid and basically a cure now. 6 years later, and on the strongest dosage they’d give, getting 3 shots with each appointment… and I was never able to spend time outside without worry of what would follow.
There has been minor improvement in controlled testing, but no noticeable benefit when actually trying to live life. I go outside near nature once each year as a test to see if there was any progress. I can’t tolerate much more than that.
Shots work well for some. They worked decently well when I was a kid, but these days, not so much. I still hope the current ones will work, as I don’t have other options, but I’m beginning to lose hope.
Privileged comment. Walks in a controlled greenhouse without allergenic pollinators also work, but the poor can't easily access either in the US.
> Privileged comment.
Shall we stop discussing any possible solution which might be out of reach for someone?
Privileged commenter. Not everyone has access to a cell phone or the internet, so they can't respond to your statement. Not to mention some people have bad dyslexia or eyesight issues. We could play this game forever, and we'd all be dumber for it.
Walking in a forest is something that much of humanity can do, and it's not a particular privilege (in the pejorative modern sense) - even if there are a small number of people that have issues that would prevent this.
Anti-allergy pills are some of the cheapest[0] and safest products on the market.
[0] https://www.walgreens.com/store/c/walgreens-allergy-relief-d... $4.99 for 24x 1-a-days
How do I bring outdoors to the wage slave office? And how do I bring light to the pre-work and afterwork when there is no sun at those times?
The practical man uses technology to offset the prison built for him. The hapless enabler farms “pithy” HN points in his LED-lit room.
Most vitamins are a waste of time and money, some are even harmful[1], but there are a lot of people with D deficiency, especially in winter[2].
1 https://www.mdpi.com/2072-6643/17/17/2744#:~:text=highest%20...
2 https://www.abs.gov.au/articles/vitamin-d#edit-group-image--...
The issue I've found with these discussions is it appears there's mixed evidence on if vitamin D *supplementation* actually has a positive impact, regardless of vitamin D deficiency. In other words, is the deficiency causal or correlative.
I have no opinion on the matter, and am inclined to think there is at least some positive benefit. But YMMV
The problem is that vitamin D doesn’t absorb the same way for everyone.
If a 100 people take 50IU of Vitamin D, you get 100 different results.
Some get enough from minor sun exposure and maybe eating a fish now and then. Others need massive doses to get any results.
50 IU is nothing. 3000 IU is something. I have MS, so I need to supplement at least 10k IU.
And yeah, it does not absorb well unless you eat some fat.
I took 10k iu via a multivitamin for a few months, and ended up with Vitamin D levels 5x higher than the maximum on the labcorp reference range. "Vitamin D toxicity"
It took many months to get the levels back to normal. Vitamin D is one of those things that once you overdose, it takes many months for the levels to slowly come down after you stop supplementing.
Be careful with Vitamin D!
The downside to having high levels is plaque/calcium deposits in arteries, if I'm not mistaken. Which can be mitigated by taking K2.
Are you aware of the history of setting acceptable levels of Vitamin D? Basically, 100 years ago, people experimented with cures for TB by giving patients one to two orders of magnitude higher dosage than the "vitamin D toxicity" levels reported today. Like insanely high numbers. Strangely enough, most people did recover from the TB, but they kept getting the treatments anyway, and that in a few instances led to bone issues. So for some reason that doesn't seem to be documented, they set the "safe level" of vitamin D to be something like two orders of magnitude lower than the level that actually caused issues. And that level has never been changed.
All of the studies I've seen around Vitamin D supplementation has shown that the "safe level" reported today is way, way lower than it should be. People appear to be just fine taking 10k IUs for months on end, even 7 years in one study. I think what we're learning is that the "safe level" is a very wide spectrum; some people could possibly be harmed from a low level, whereas some people are perfectly fine at a very high level.
Yes, and many people are fine with 10k IU for months because their body just does not absorb it well.
And some people, like those with MS (such as I) need to take more than usual. Someone I know has MS and takes 20k IU and gets regularly tested.
And, fixed dosage never makes sense with Vitamin D. If you're supplementing, you need to make sure you regulate it based on sun exposure, since it's literally the Sun vitamin.
It's easy to double up if you decide to eat lunch outside because the weather is nice this month. I take 10k only if I'm indoors all day, and reduce or take none if I'm out.
> An excess of vitamin D causes abnormally high blood concentrations of calcium, which can cause overcalcification of soft tissues, including arteries and kidneys. Symptoms appear several months after excessive doses of vitamin D are administered. A mutation of the CYP24A1 gene can lead to a reduction in the degradation of vitamin D and thus to vitamin toxicity without high oral intake (see Vitamin D § Excess).
> Treatment
> In almost every case, ceasing vitamin D intake, combined with a low-calcium diet and corticosteroid drugs, will allow for a full recovery within a month. Bisphosphonate drugs (which inhibit bone resorption) can also be administered.[2]
Regardless, blood levels need to be checked for this sort of thing and doses are not one-size-fits-all. I also once was taking 10k daily, for several months, and ended up just barely in excess territory with no noticeable symptoms. (I settled on taking 4k daily in the long term.)
> In almost every case, ceasing vitamin D intake, combined with a low-calcium diet and corticosteroid drugs, will allow for a full recovery within a month.
Surprised to see just 4 weeks for a recovery. I got retested after 8 weeks (only minor improvement) and wasn't until 16 weeks until the test finally came back in range.
100% no dose is one-size-fits-all. I overdosed from taking a specialty multivitamin (it has a discord channel and everything). So was chatting with people taking the same vitamin, same dosages, also getting tested, but others had no issues at the same doses.
I guess I just absorb vitamin D with great efficiency, who knows.
> An excess of vitamin D causes abnormally high blood concentrations of calcium
That is what supplementing K2 with D3 is for, too.
Yeah, you should take vitamin D with K2 at the very least.
Thanks for the tip though. I do not take it regularly so I think I'm fine. :D
Echo this with a PSA: it's a simple test to get your levels, and I'm a proponent of ensuring it's included when you have other regular blood tests (may have to ask for it). That can allow a person to see patterns, how effective any supplementation (and different amounts) are, etc.
I can use myself as an example: I have crohn's disease and I can take doses of 50000UI for some weeks, then 4000UI daily and after a year have my Vitamin D results as low as 20ng/ml.
50IU is a minuscule dose though, no? If people are recommended to supplement, they generally take a dose in the range of a few thousand.
The point wasn't the dose, I just picked a number out of my ass.
The point is that from that N IU the 100 people will absorb anything from 0-N, it's very individual and varied.
The only way to be sure is to test your levels, which costs money every time. There really should be a simple and cheap home test kit for it. You'd sell millions every year just in the Nordics and Canada =)
Maybe this comes across snide, but have you been to the Nordics? I can get tested at my GP for free practically as often as I'd like, I doubt you'd sell too much in the way of home test kits.
Been living here my whole life.
I've been offered a (free) Vitamin D checkup exactly zero times. We should be getting them though, dunno why we don't.
i'm guessing he meant 50k not 50. 50k is quite a large dose.
There is no way that's what they meant. 50k is an absurdly large dose that's way outside the safe intake range. 10k is used sometimes under medical supervision and even then it's a very short term measure. For long term intake, 4000IU is a widely accepted safe upper limit. 50k is an order of magnitude more than that.
There's plenty of documentation of people taking 50k for a period of time and having no side effects. There's been something like a dozen trials using high doses like this to treat TB, and they're usually successful, with no significant negative symptoms.
Conversely, some studies have shown that 4k IU does contribute to hypercalcemia in a small number of cases (4 per 1000). So actually 4k is deemed "not completely safe" as a limit.
The point is, the amount you take needs to be adjusted by a clinician, as the safe range for you is unknowable otherwise.
If your doctor is not seeing results they’ll keep upping the dose and I’ve heard of some that sound like an attempt at assisted suicide. Most of us would get toxicity from some of the ones I’ve heard.
My family is in this group. We are poor absorbers of vitamin D, some of my elder relatives need 5 times the "safe upper limit" to have healthy blood levels. As long as you're checking your blood values routinely (and for both D2 and D3, not just one or the other), it's reasonably safe. Sort of like other prescriptions in general.
I heard about a guy who ordered a bottle and ended up with vitamin D poisoning, on one of those Ira Glass style podcasts. Turns out they forgot to compound it before sending it out so he was getting “cask strength” vitamin D. Sounded very unpleasant.
Most of the vitamin D supplement studies have been very low quality in that they give all subjects in each group a fixed amount (or placebo). Ideally they should periodically test blood levels and titrate the dose to hit a target range. This would get us closer to establishing causality (or lack thereof) including a response curve. The amount needed to hit a given target will be wildly different for many individuals based on factors that are still not well understood.
Just my results (n=1) and I don't think this is exactly what you were saying, but just in case other read it the same way I did at first: having had (lab tested) vitamin D deficiencies, vitamin D supplementation can help to restore levels back into the desired range. So supplementation can have the desired effect of improving vitamin D levels (more below). It is a simple test that most doctors don't quibble about adding on to other blood tests (i.e. during annual checkup, for instance), but isn't generally checked by default. (note: insurers may want it to be "diagnostic" rather than "preventative" in order to cover the test.)
Whether it has a "positive impact" on overall health (which I believe to be your point), that would be even more anecdotal and also impossible for me to narrow down whether that one factor had any significant effect, so I won't posit that. And I agree that from different studies I've read, the actual science on it is pretty varied and I haven't seen anything conclusive. Even this study notes their conclusion was "... among adults with suboptimal baseline vitamin D levels".
This is solely my own anecdote, but I used to get bad seasonal depression every winter. I tried a number of interventions short of medication; none moved the needle very much. I started supplementing with vitamin D probably 8 years ago and haven't had any issues with seasonal depression since.
I'm pretty personally convinced that it was the supplements that helped here.
I tried a 1000 IU vitamin D pills to no avail. Bumped it up to 5000 IU and still saw very marginal bumps in my blood tests
I think I might try daily 10000IU after showing my doctor how little it's moving the needle for me
I was put on prescription vitamin D2 50000 IU and it caused a bunch of side effects for me including heart palpitations for over a week and then a paradoxical reaction to magnesium causing them to be even more intense.
Proceed with caution and listen to your body. Doctors were accusing every other thing than accepting whatever it did to my calcium / other electrolytes bothered my heart.
Interesting, my levels have always been chronically low and I feel no effects from daily 5000IU
That's still 15000 IU under my weekly dose so maybe you just haven't hit the threshold I hit.
It's expensive in the US because one company has exclusive sales here (patent protection?), but you could try calcefidiol, weekly dose and is supposed to get levels up rapidly. Apparently it's the common form to take in Spain, and it's further down the metabolic pathway vs cholecalciferol. (I take but still have to get levels checked)
thank you, will have to check this out
I can tell you supplementation works 100%.
I took a blood test several weeks ago, my Vitamin D level was 14 ng/ml. I was so fatigued there were times I had to lay on my office floor because I didn't even have the energy to sit in my chair. I started taking 50k IU's weekly and then 10k IU's daily, and the results were dramatic. I went from having 0 energy to nearly normal. I also had soreness in my legs which went away.
Vitamin D isn’t technically a vitamin in the strict sense, because unlike the other vitamins the human body can produce it itself (by exposure to sunlight).
The body can also synthesize vitamin A from beta-carotene which is effectively two vitamin A molecules joined together (one rotated 180deg relative to the other).
Dogs can synthesise vitamin C…
Sure, many things are vitamins for one species but not another. (In fact, every vitamin must be able to be produced by at least one species – where else would it come from?)
Wow, that is interesting. They can synthesise it in their liver?
Many animals can. There are a gene for it, humans don't have it. There is a lot of speculation as to why, but nothing really stands out (possibly just random chance - if you eat enough there is no advantage to keeping the gene and in turn no loss from losing it. However I'm unable to rule out other possibilities) https://pmc.ncbi.nlm.nih.gov/articles/PMC3145266/ is a really interesting survey of the issue across many different species.
From the article: > Another argument supporting the suggestion that species which have lost their GLO gene were under no selective pressure to keep it, is that all species which have lost their GLO gene have very different diets but all of them have diets rich in vitamin C
What would a diet poor in vitamin C be considering that "everything else" makes it? I guess root vegetables? It feels like, if anything, this would imply a GLO gene decay more often than has happened, no?
That is probably a question for a nutritionist not me. My understanding is Grains, root vegetables, and meat are all low in vitamin C. Likely other things as well. But I'm not a nutritionist (I've read enough that I think I'm right here, but not enough to state it with confidence), so take the above with plenty of salt.
[dead]
And humans aren't dogs.
Most definitions of the word vitamin are not specific to humans. Wikipedia talks about "organisms", Britannica about "higher animal life", Webster about "most animals and some plants"
What is and isn't a vitamin by definition varies from species to species.
I don't agree. As with everything, it requires care. Taking a multivitamin and thinking you're good to go is delusional.
For most people just eating a good balanced diet and they are good to go. There are a few with genetic/biological issues and they need more - ask your doctor. Vitamin D is one that modern lifestyles likely don't get enough of and so probably worth it - again talk to your doctor.
If eating a "good balanced diet" were easy/normal, we'd have close to zero disease. Supplements are definitely a way to get as close as possible to balance when day to day food intake is chaotic.
there is no reason to think a good diet will prevent disease, nor that supplements will help in most cases. Good diet will prevent some disease, but disease is natural in the environment and good diet is mostly your immune system has what it needs to fight it off after you get it.
ErikCorry, bluGill and others like them get people killed with their exceedingly harmful assertions. It is pointless to argue with them since they're here to spread harm, also probably working for big pharma. The best that one can do is ask the reader to find the evidence for themselves.
[flagged]
How do you feel about vaccines and Tylenol?
Uncalled for. GP is pointing out that the fact the human body can produce Vitamin D means it is not a vitamin.
vi·ta·min /ˈvīdəmən/ noun any of a group of organic compounds which are essential for normal growth and nutrition and are required in small quantities in the diet because they cannot be synthesized by the body.
This paper states:
> The study protocol was approved by the Institutional Ethics Committee and registered with the Clinical Trials Registry of India
As far as I can tell, that registry is here: https://www.ctri.nic.in/Clinicaltrials/pubview.php
Doing a keyword search for the first author's last name reveals zero hits. (It's possible I'm missing—that search does not inspire confidence.)
Glad to see this study, seems decent, but for a different perspective there was a relatively recent meta-analysis on the effectiveness of Vitamin D for RIs that suggested no effect:
https://www.thelancet.com/journals/landia/article/PIIS2213-8...
One significant difference in this study is that it focused on people with low baseline vitamin D (10-30 ng/mL 25(OH)D), and moderate intervention (2000 IU daily).
The meta-analysis you posted did perform subgroup analysis on people with low baseline vitamin D (<25 ng/mL), but this included a wide range of intervention levels, 90% of which were <2000 IU daily equivalent. They also performed subgroup analysis on high intervention levels, but this included a wide range of baseline vitamin D, 90% of which were >25 ng/mL.
And also there's a difference between infection incidence, intensity, and duration, the evidence I've seen has been strongest in reducing intensity and duration. Also dosage might just be too low.
I've been feeling a little off lately with some respiratory symptoms and took 25,000 IU of Vitamin D, in people who are deficient (probably me lately) 400-1000 daily dose might not actually do enough to have an effect.
It's about time for a meta-meta analysis comparing the traits of the different sets of papers (N, dosage, deficiency status, time of year, duration/incidence/intensity, etc)
I live in Winnipeg, Manitoba where it is quite cold for a big majority of the year. I have dabbled with supplements because I get a couple of major colds every year.
I've heard things like you only need 15 minutes of sunshine per day to get your recommended dose of Vitamin D, but I've also heard it can be quite bad for you if you have too much in your system (and it's hard for your body to flush excess amounts).
If there a safe level of Vitamin D supplements where you won't run this risk? I don't drink milk either because I'm lactose intolerant.
"Winnipeg, Manitoba" ... "only need 15 minutes of sunshine per day to get your recommended dose of Vitamin D"
That doesn't apply to you most of the time, unfortunately. Vitamin D is the result of UVB exposure. For significant portions of the year, you don't get very much [1], compare with, say, [2] Orlando Florida in the US. 10-15 minutes is for a UV index of 7 [3], so that's only 4-6 months out of the year for you. And just based on my couple minutes with Google here, that number may also include the assumption that you're not just "out in the sun" for 15 minutes, but basically sunbathing. Lesser exposure may take longer: [4] Winter times can be effectively impossible because you can't sunbathe at 10 below (regardless of which scale I'm talking about) and you're not going to spend the requisite hours in the sun for what little skin is exposed. Or they can be outright impossible if your skin is dark enough.
[1]: https://winnipeg.weatherstats.ca/charts/forecast_uv-monthly....
[2]: https://nomadseason.com/uv-index/united-states/florida/orlan...
[3]: https://overcomingms.org/program/sunlight-vitamin-d/uv-index...
[4]: https://vitamindwiki.com/dl2105?display
I grew up on the Canadian praries. -10C is basically shorts weather.
edit: seriously though, anything warmer than -10C you'll definitely see kids in shorts. I go skiing in shorts every year.
Wear a g-string if you want. It doesn't make the sunlight any brighter in winter.
But it does expose more skin, which [3] recommends!
Sadly, it doesn't say how long you should exposure yourself with a UV index of 1, which is what Winnipeg has today, and it's not even proper winter yet.
Yes, yes, you're an invincible winter god upon whom the temperature means nothing. Let us all acknowledge that and bow before you.
Now tell me everyone is doing that, all the time. I also live fairly north, which is part of why I've learned this about Vitamin D in my own research, and I can't help but notice that stores selling winter coats and gloves and other assorted cold gear don't go out of business ever year because nobody is buying them. Nor do I walk through a crowd of people in the middle of winter and have people point and laugh at me because I'm the only one in a coat.
Come on. You're just arguing to argue and swagger a bit, not because you actually think people are getting enough sun exposure in the middle of winter to get enough Vitamin D and there's nothing to worry about.
Just because you're a jerf, doesn't make me one too. Stores aren't going out of business because it gets below -10 regularly.
I'm not sure that people downvoting you have been around northerners much. Down here in the upper midwest US, we tend to consider 4 or 5C to be shorts weather in the spring. I've a friend who would wear flip flops / sandals outside down to roughly -10C.
Then again, most people aren't getting the equivalent of 15 minutes of index 7 UVB exposure at those temperatures, so it's not quite the same thing, but still.
People are downvoting because it has nothing to do with the comment they're replying to or the original post. Most people are well aware temperature is relative too, I live in the American South and there are certainly people here who will wear shorts in cold or freezing weather too.
> Winter times can be effectively impossible because you can't sunbathe at 10 below
I take 5000 IU per day year round and have not had any issues. Research suggests you can dose 10x that without major problems, although personally I wouldn't go higher than I am already.
https://pubmed.ncbi.nlm.nih.gov/30611908/
That sounds like a lot:
To help prevent vitamin D toxicity, don't take more than 4,000 international units (IU) a day of vitamin D unless your healthcare professional tells you to. Most adults need only 600 IU of vitamin D a day https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...
Part of the issue with vitamin supplements is that the bioavailability can be unpredictable. The actual amount absorbed can vary between 10% and 100% depending on the time of day, supplement formulation, what foods if any are taken together, as well as the particular characteristics of the individual's intestines, which are difficult to assess. Because supplements are not regulated as pharmaceuticals in the United States, this variability can be severe; in the worst cases, supplements do not even contain the active principle.
So, I am not surprised that someone needs to take 5000 IU to get 600 IU worth of effect. Institutional medical authorities are (rationally) quite defensive when cautioning readers about supplement consumption; they must consider the worst case (100% bioavailability) when assessing the risk of overdose.
As an alternative to vitamin supplements, exposing common dietary mushrooms to ultraviolet light converts (by an uncatalysed photochemical reaction) the ergosterol therein to calciferol. How best to achieve this in a home setting is unclear.
One number is not going to work for everyone. The only way to be sure is to get a blood test for Vitamin D levels. I get tested with my yearly physical, but if someone really cares they can get more frequent blood tests.
As has been commented elsewhere, everyone absorbs vitamin D differently, this really is a matter where someone should just get tested, if they (and their doctor) decide supplementation is needed, do so, test again, and adjust dosage accordingly until desired levels are attained.
Not medical advice here, but harmful effects from vitamin D exposure/toxicity generally only happen at very high levels, or if high doses are taken over long periods of time (as excess can be stored in fatty tissue/liver). Doctors often prescribe a very high dose (like 50,000 IUs) for individuals who are very deficient (often taken once a week, not daily) for a short period before going on a more standard (400-2,000, maybe 5,000) IU dose for maintenance.
The advice on this is all over the map and that's a big problem in the space. Reputable medical sources have recommendations almost two orders of magnitude off from each other at times.
This article, for example:
https://www.ccjm.org/content/89/3/154
...cites several cases where daily supplementation of 50K IU was required to restore normal D levels, although also a case where that same dose caused toxicity. As one of the other commenters in the thread noted, working with your doctor to establish the right level is probably the right move. If nothing else, they have the capability to test your serum levels to see where you're at.
I experimented with taking 10,000 IU a day for about a year. I had my D levels checked with my normal yearly blood test (lipids, etc) and it put me into the high normal range. I still take 5000 IU daily and have for years with no ill effects.
I should note that I live in a place that sees little sun for five or so months a year.
You can't possibly have the same recommendation for all geographies. Florida and Scotland have somewhat different level of UVB especially throughout the winter, come on.
Vitamin D toxicity is a legitimate concern, so those dosing should be mindful of it, depending on dosage and existing serum levels. Don't action on medical advice from strangers on the internet alone, talk to you doctor or other credentialed medical practitioner you work with if needed.
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
It's bad for your kidneys
You probably have to really try to take too much Vitamin D with any over the counter supplement (<=5,000 IU), especially if you live that far north. For reference, a prescription dose for someone who is low is usually 50,000 daily.
It should be part of your standard blood tests so you should know if you're running high or low and your doctor can recommend or prescribe a good dose.
I’ve had a prescription twice and it was 50,000IU of D2 once weekly. Usually the OTC one people buy is D3.
If you dry your mushroom the sun they generate a crap-ton of d2. There was a study earlier this year.
With 5,000 IU sometimes taking several at a time I had blood levels of Vitamin D at the top of the range which wasn't dangerous it was just informative, "hey you're having enough, tone it down".
It's 50,000 weekly.
First know that the body will stop making vitamin D before you reach overdose quantities. This means you should take vitamin D in the morning.m rather than the evening. Second know that vitamin D is fat soluble. So if you are losing weight, you can more easily overdose if you have high levels stored in your fat. Also know the body won’t absorb as much vitamin D if you don’t take it with fat.
This can make dosing tricky. You can be taking an amount that is safe right now, but then is too much later.
You can max out your body’s vitamin D production even on a cloudy day, though the sun’s angle of incidence effects production.
The body typically maxes production at something like 20k iu (pleae verify this number it has been a while since I learned it), so staying below this number should mostly safe.
The USDA has set its recommended daily allowance mostly to avoid rickets. It is largely considered too low a number for general well being.
I live in north western Washington, and previously used to combat seasonal affective disorder, with some pretty dark thoughts come february. Since I started taking 1k D3 some 20 years ago much of the seasonal mental health has gone away. I take 2k D3 consistently currently, and if I run out for more than a week my mood starts to deteriorate quickly. I still haven’t proved causation since there are likely reasons I’ve let myself run out of the supplement that long, but it is so consistent that I treat it as causal at this point. YMMV
Please do research above just asking a forum for dosing advice though. This is a well educated place, and I would very much trust it as a starting point, but there is a lot of good published content on the topic. Though, I admit google is so bad today, I might fail to find any of the content I referenced years ago… if you use chatgpt make sure to require references, and check them. I find that using multiple instances to review research references separately prevents some context based poisoning as well. And pointing out inconsistencies can be a good way to find nuance in a topic. Though sometimes LLM will just waffle, and the context may be done
I've heard the 15 minutes is all you need. I've also heard that in winter the sun is so weak that no amount of sunshine gives you any. (even if you were naked outside in winter - risking frostbite).
I'm not a medical doctor. I cannot evaluate any of the above claims. I wish I could find a source I could trust.
Depends on where you are. Latitudes above roughly 35 degrees N, the sun is too low in the sky roughly between October and March to allow for UV-B rays to penetrate, which is what your skin needs to synthesize vitamin D.
So yes, if you live in the northern regions, you don't produce any at all from sun exposure, even on a bright sunny day, during most of the year.
Up here in the PNW, even in the summer, you only have a window of roughly 4 to 5 hours where the sun is high enough, in July.
You can get blood tests pretty cheaply. The safe level is the level that, after you take it consistently, has you in the desired range on the test.
I've heard things like you only need 15 minutes of sunshine per day to get your recommended dose of Vitamin D
The figure I read years ago was that it takes 15 minutes in short sleeves to get the necessary light exposure at the 45th parallel in winter. I'm right at the 45th parallel and I don't go out in short sleeves in the winter, so I imagine it's significantly worse for you!
You don't need to guess, go to your GP and get yourself tested. It's not expensive, depending on where you're from it might even be free, and usually you get the results back already the next day.
EU considers 600 I.U. per day as safe. Probably not enough if the level is low. Blood sampling is cheap, why don’t you have it checked.
25000 IU weekly during winter is OK, for an adult
An adult with 60 kg or 160 kg of mass?
It's possible to overdose on Vitamin D, but you have to eat absurd amounts.
Unless you eat the pills like candy, you're safe.
Generally agree, but unlike water-soluable vitamins, vitamin D can store excess in fatty tissue and the liver, and so if a person takes a large dose (generally 10,000 IU daily or more), they could develop toxicity over time due to the build-up. That's why it's important to test and adjust dosages according to the data.
Untrue. Source: painful personal experience.
How much were you taking?
I don't remember because it was 25 years ago. Not a huge amount.
I take 8000 D3 (+200ug K2 MK7) daily and I'm fine. since covid I go like this for entirety of winter and then back down when summer comes. Perhaps you live in a climate where you get a lot of sun exposure and somehow overdosed on that. A guy from vitadmindwiki.com even says that you'd have to take 14000IU daily for a year until reaching toxicity limit (although this guy tends to sometimes say different things on the same topic, so I'd be cautious on whether this is the exact amount) https://vitamindwiki.com/Overview+Toxicity+of+vitamin+D
Although it'd be great if you explained what exactly happened, perhaps it wasn't a result of taking vitamin D itself but rather some external thing. Judging by "painful experience" I assume kidney stones, which could be caused by too much calcium or genetic preference. not a doctor or an expert on the topic though, just open for a discussion :)
The symptoms are hard to describe (but did not include kidney stones), but it was obvious that something was drastically wrong and the drastic wrongness went away in response to my completely avoiding all sunlight and dietary sources of vitamin D and my doing a few other things described below.
Most people could probably take as much supplemental vitamin D as I did without incurring this adverse effect, but there is no straightforward way for a person to know whether they are in the minority of people who will incur the effect. (I do remember that having Northern European ancestry makes the effect more likely.)
The drastic wrongness started showing up after only a few months of whatever high dose of D I was taking (and I regret that I cannot provide this information: I did search for it briefly; but it was definitely not an "absurd amount") so if you've been taking the 8000 D3 for years, then the drastic wrongness is unlikely to suddenly show up in your case -- and if it does show up it would probably be because you contracted some sort of chronic infection.
The presence of certain kinds of chronic infections and genetics are the main causative factors according to the information I relied on 25 years ago. Actually, here is the basic information. I followed most aspects of the protocol including my obtaining a prescription for olmesartan, but then I lost interest when the drastic wrongness went away (after not much longer than 4 months IIRC). I was also probably on an antibiotic during this recovery.
https://mpkb.org/home/patients/protocol_overview
P.S., I take as much MK7 as you do (i.e., twice as much as the "suggested usage" on the label) and have for many years, just without supplemental vitamin D.
Most interesting, will bear that in mind. To this date I haven't encountered any "drastically wrong" symptoms with my d3 usage and frankly haven't heard that much about any adverse events linked to vitamin d3. If you feel comfortable with that then you could disclose what exactly is that adverse effect you've been experiencing, but I see that you try to avoid this topic so no pressure :)
It's not that I'm unwilling to publish the information: it is just that I despair of putting into words how I knew something was drastically wrong with my physiology -- especially now that 25 years have gone by.
A few other interesting links with Vitamin D absorption. Surprised nobody has brought up gut dysbiosis and the role microbiome plays in Vitamin absorption. I'm finding it increasingly difficult to discern whether the things we consume are for the direct benefit of our cells and metabolic needs or via a more indirect path if the things we consume directly affect the microbiome within us which then translates into either nourishment or inflammation within us. Since microbiomes can change rapidly in composition, this feels like a game of nurturing over the long-haul with some minor blips along the way.
[1] "connection between vitamin D and the immune system through gut bacteria and may have applications for improving cancer therapies"
[2] "How the Gut Microbiome Affects Vitamin D Absorption"
[3] "vitamin D may affect the host-microbiota relationship."
[1]: https://www.science.org/doi/10.1126/science.adh7954
[2]: https://www.gutnow.com/medical-treatments/how-your-gut-micro...
[3]: https://journals.asm.org/doi/10.1128/spectrum.00083-24
I take 10k IU of vitamin D if I feel a cold coming on. I used to get extremely bad colds very frequently, and every time I get frustrated and read whatever research might be helpful. A year ago I came across some info about LL-37, and found that vitamin D might help, and that's when I started taking it. https://pmc.ncbi.nlm.nih.gov/articles/PMC9134243/
The big dose of D seems to help. I'm certain I'm deficient, since I already take 2-4k daily, which noticeably helpsy winter blues. It's the first time I can "arrest" a cold, and even if I get sick the symptoms aren't nearly as bad.
My full protocol for if I start feeling a cold is this:
1. 10k vitamin D 2. Stay extremely warm when I sleep. Uncomfortably warm. 3. Butyrate (probably a placebo) 4. Curcumin (almost certainly a placebo).
Take like 2g of Vitamin C. It's a lot stronger. Vitamin D is good too, but if anything you want to take C.
I personally found that taking vitamin D regularly dramatically reduced how many colds I got (10 in 2024 vs. 1 in 2025).
I take 2,000 IU per day, typically without a meal.
> typically without a meal
any reason why? it's fat soluble and absorbs much better if taken with a meal.
Because I always forget lol. My point is that I still had a good effect even though I'm doing an extremely sub-optimal job of taking it/probably getting a dose-equivalence of way less than 2k IU/day.
Unfortunately this is a common error people make, many vitamins and other supplements are absorbed better when taken with food, even if that seems counterintuitive at first.
It really depends. Other things like iron is best taken fasted (and paired with Vitamin C). Coffee also blocks iron absorption, so many people supplement at nighttime. Also things like Zinc and Copper both compete with each other for absorption, so best to avoid taking them at the same time.
If you're optimizing your supplement stack, really gotta research each one individually (and how each impact the absorption of the others)
Another thing I am curious about is time of day too -- I was told vitamin D/Multivitamins were better taken in the morning with food.
In the US it is very easy to test your vitamin D levels. I recently had mine done and was just below normal range. Started supplementing and will test again in 6 months.
A lot of people are critiquing the statistical methods and quality of the study, which is fine. But it's worth pointing out that you—the individual—should not be concerned with someone else's p-value. You should be concerned with maximizing your own utility. A safe, possibly effective, and cheap intervention is probably worth trying. If it was more expensive or less safe, it would require more evidence to try.
There can be hundreds of safe, possibly effective, and cheap interventions. Can’t try them all. Higher quality of evidence helps narrow it down.
Take it from an academic like me that peer review in just over a month is rare and a sign of low-quality editorial work at the journal (the exceptions would be the most open, progressive journals like PCI and similar).
The formatting/style and peer review history alone are enough for me to doubt this. Of course, the other users' points about study design and lack of transparency make it even harder to trust the claims.
Do we really know what "optimal" vitamin D levels are? I've heard a wide range of answers on this, and it's not even clear to me that we know whether there is natural human variability in the amount needed.
I haven't seen convincing evidence that vitamin D supplementation is materially useful for anything but rickets. I get the impression that naturally high serum levels are an effect rather than a cause of other positive things, and that supplementation mostly increases serum levels without effecting positive things. It doesn't seem harmful either, so can't hurt might help?
What about the article that that talks about Vitamin D being the same chemical as rat poison and that the positive effects it has on our bodies may be due to the fact that we are low-level poisoning ourselves with it?
"Vitamin D3, also known as cholecalciferol, is used as a rodenticide because it is highly toxic to rodents when ingested in sufficient quantities. It functions by causing a life-threatening elevation in blood calcium and phosphorus levels, leading to severe acute kidney failure"
"Despite its use in rodenticides, vitamin D3 is safe for humans and pets when consumed in normal dietary or supplement doses. However, extremely high doses of vitamin D3 can be toxic to humans as well, potentially leading to hypercalcemia, kidney stones, and renal failure. The difference in susceptibility between rodents and humans is significant; rodents are much more sensitive to the effects of cholecalciferol, which is why it is effective as a rodenticide."
The theory is that we are just poisoning ourselves by taking it and that our bodies react to being poisoned with the positive effects that are well documented and observed.
Reminder that the Recommended Daily Allowance of Vitamin D found on all the labels (800 IU) is mistakenly too low, by a factor of 10x, due to a maths error (should be 8000 IU). It has not been corrected yet. Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC5541280/
Supplementing with vitamin D is honestly one of the easiest things you can do... it's cheap, available everywhere, and makes a real difference. Just make sure you're also taking magnesium citrate (or another good form of magnesium) with it, since your body needs magnesium to properly use vit D
An even better option is to go to your GP and have them run your bloodwork. It's cheap, depending on where you're from it might even be free, and you don't have to guess or randomly pick supplements you read about online. Most people on HN will live to a very high age, there's no reason to take random gambles on what you do to your body.
For sure, you're essentially flying blind without bloodwork. I get a full panel at least 3x/year.
And K2.
As for magnesium, I would go with magnesium glycinate or magnesium threonate.
Absolutely. And you're totally right about magnesium glycinate. That's what I take. I don't know why I said citrate.
https://www.economist.com/science-and-technology/2025/09/17/...
Can confirm anecdotally. I used to get 2-3 colds a year for about 15 years straight, especially during season changes when the humidity levels changed. Started taking 5000 IU vitamin D3 daily about 2 years ago and I haven't gotten sick since.
I was pretty sure we already knew vitamin D deficits dampen the immune system.
I'm confused - Vit. D is essential for the immune system and most people are deficient - why isn't this obvious.
I wonder why we didn’t recommend vitamin D during Covid?
There were a few soft recommendations. Specifically I remember an ER doctor in 2019 saying vitamin D seemed to be a differentiator in the sample of cases he was seeing in the ER (everyone was starting to panic) and the CDC walking it back as unsubstantiated. I mentioned it at work, then 10 days later my boss's boss asked me where I had heard it, because he had heard the same thing.
There have been a number of people on HN who have attributed any measurable COVID benefit of Vitamin D, to a confounding variable, as recently as 3 months ago - https://news.ycombinator.com/item?id=44705486 The Big Vitamin D Mistake
One of the best treatments is interferon. It's something you will also produce yourself, with therapeutic effect, if exposited to sunlight or the infrared light used in red light therapy. Here's a video about it, from a continuing education provider: https://www.youtube.com/watch?v=oRkxH56LqCo
Vitamin D therapy doesn't have such an effect.
Because the right people couldn't make money off of it - same reason that a lot of beneficial treatments were not recommended or flat out defamed.
I wonder if adding zinc on top of this would do.
Would do...? Zinc taken the first day of symptoms may reduce the duration of a cold by a day on average. It's probably useful, but not certain.
Be sure to take zinc with meals, or your stomach may hate you.
3-4 years ago this submission would be flagged in seconds just because of the word Vitamin D.
Heliotherapy is well-due for a resurgence. One of my favourite youtubers (conquer aging or die trying) has a great interview with a medical doctor about sunlight as a medical intervention. Well worth the watch:
https://m.youtube.com/watch?v=UF8UE6cJaWQ
That's Doctor Roger Seheult, MD, who hosts videos for continuing education provider MedCram (https://www.medcram.com/). They post lots of free videos on their YouTUbe channel (https://www.youtube.com/channel/UCG-iSMVtWbbwDDXgXXypARQ) and several of them cover the research behind heliotherapy.
Newsflash: When you are sick, addressing comorbid conditions helps you get better faster.
Yeah, this is a crucial point. This is studying "adults with suboptimal baseline." If you have a vitamin deficiency and get sick, I would expect supplementation with that vitamin to provide some relief, regardless of which vitamin it is.
This does not mean that the same will happen for people who did not have a deficiency.
Having said that, there is good evidence that Vitamin D deficiency is widespread, and supplementation of Vitamin D is relatively safe unless you take excessive amounts.
Interesting how your government did not mention Vitamin D during the COVID scare.
Breaking news! Water proven to clench thirst among those who are thirsty!
So a vitamin deficit is bad for your health.
Shocker.
Just turn on an uv light for a few hours. Problem solved.
Anecdotal but when I'm sick I double my vit C and D intake which typically helps me.
IANAMD.
It is my general understanding that unless you are severely deficient, Vitamin D supplementation generally takes weeks to bring levels up. It's unlikely that taking it for a few days is going to have any measurable impact on your recovery from illness unless you are severely deficient and/or taking MASSIVE doses, which may or may not be recommended depending on your prior levels and BMI.
See more here: https://www.ccjm.org/content/89/3/154
e: fixed broken URL
Very interesting thanks for sharing!
Same... In our family we start taking Emergen-C a few days before we travel also.
Which is very overpriced and doesn't do anything unless you're deficient. Excess vitamin C does nothing, it goes right through you.
> which typically helps me.
Uhm, how can you get to that conclusion? I mean: how can you compare the evolution of a cold with and without the vitamin surplus?
Very well could be a placebo
Reminds me of the old, with treatment, most colds will be cured in just 7 days! Without treatment they generally last about a week.
That said, do not underestimate the health benefits of the placebo effect. It can help a lot. Particularly with anything to do with stress.
So your statement should have been, "it seems to help."
Unfortunately Vitamin D deficiency tests (probably it is not covered by your insurance), high dose supplements are currently pushed so much by Doctors I started to think this is almost a scam. Most of the research about the subject are very noisy and conflicting.
If there is any reason for the test, it would be diagnostic and not preventative, and that is generally covered. Just checking cause you want to know your levels generally wouldn't be, but there are any number of symptoms that could be related to that.
As for it being a "scam" - there are enough valid studies that show what this one did, that folks who are deficient that are able to raise their levels tend to be slightly healthier.
There isn't necessarily evidence for supplementation beyond "normal" range, and I do agree that no one should just take high-dose vitamin D supplements without data (tests) that it is necessary.
If it's a scam, who's profiting? The pills are dirt cheap, generic, and over the counter.
Dr. Michael Holick: https://www.nbcnews.com/health/health-news/selling-america-v...
Interesting article, thanks!
Tests are very expensive
How much are they where you are? They're 20-30 EUR on their own in Germany (doctor's office, pharmacies)
It is more than double of that, plus doctors prescribe fancy high dose vitamin D, Adds up to more than 100 euros.
"Exercise" not found in the shared text.
I'm sure people who supplement or have good D levels also take care of themselves, generally - because they know D is one of the supplements that make a difference both somatic and psychological.
And thus do better with flu/cold.
It is a double blind study. what else do you want for confirmation ?