-- 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.
"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/
> 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.
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..
Man keeps trying to bring the outdoors inside.
The UK also consumed a lot more liver than it does today I imagine...
Man want both good of indoors and good of out outdoors.
The practical man uses technology to offset the prison built for him. The hapless enabler farms “pithy” HN points in his LED-lit room.
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--...
I have no opinion on the matter, and am inclined to think there is at least some positive benefit. But YMMV
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.
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".
I'm pretty personally convinced that it was the supplements that helped here.
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.
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.
> 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.)
https://www.thelancet.com/journals/landia/article/PIIS2213-8...
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.
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'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.
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...
edit: seriously though, anything warmer than -10C you'll definitely see kids in shorts. I go skiing in shorts every year.
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...
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
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.
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'm not a medical doctor. I cannot evaluate any of the above claims. I wish I could find a source I could trust.
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.
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!
Unless you eat the pills like candy, you're safe.
[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...
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).
I take 2,000 IU per day, typically without a meal.
any reason why? it's fat soluble and absorbs much better if taken with a meal.
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.
As for magnesium, I would go with magnesium glycinate or magnesium threonate.
"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.
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
Vitamin D therapy doesn't have such an effect.
Be sure to take zinc with meals, or your stomach may hate you.
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.
Shocker.
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
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?
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.
And thus do better with flu/cold.
