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Vitamin D reduces incidence and duration of colds in those with low levels
- AbstractH24 11mo agoNewsflash: When you are sick, addressing comorbid conditions helps you get better faster.
- InsideOutSanta 11mo agoYeah, 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.
- kacesensitive 11mo agoAnecdotal but when I'm sick I double my vit C and D intake which typically helps me.
- pif 11mo ago> 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?
- kacesensitive 11mo agoVery well could be a placebo
- btilly 11mo agoReminds 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.
- IAmBroom 11mo agoSo your statement should have been, "it seems to help."
- garciasn 11mo agoIANAMD. 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 https://www.ccjm.org/content/89/3/154 e: fixed broken URL
- kacesensitive 11mo agoVery interesting thanks for sharing!
- supportengineer 11mo agoSame... In our family we start taking Emergen-C a few days before we travel also.
- driverdan 11mo agoWhich is very overpriced and doesn't do anything unless you're deficient. Excess vitamin C does nothing, it goes right through you.
- thrusong 11mo agoI 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.
- dooglius 11mo agoYou 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.
- mwigdahl 11mo agoI 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/ https://pubmed.ncbi.nlm.nih.gov/30611908/
- toomuchtodo 11mo agoVitamin 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&query=Vitamin%20D%20toxicity%20&sort=byDate&type=comment https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
- ErikCorry 11mo agoThat 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-healthy-eating/expert-answers/vitamin-d-toxicity/faq-20058108 https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...
- zemvpferreira 11mo agoHeliotherapy 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 https://m.youtube.com/watch?v=UF8UE6cJaWQ
- dlcarrier 11mo agoThat's Doctor Roger Seheult, MD, who hosts videos for continuing education provider MedCram (https://www.medcram.com/ https://www.medcram.com/). They post lots of free videos on their YouTUbe channel (https://www.youtube.com/channel/UCG-iSMVtWbbwDDXgXXypARQ https://www.youtube.com/channel/UCG-iSMVtWbbwDDXgXXypARQ) and several of them cover the research behind heliotherapy.
- ErikCorry 11mo agoMost 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%20intakes%20were%20associated%20with%20an%20increased%20cancer%20risk https://www.mdpi.com/2072-6643/17/17/2744#:~:text=highest%20... 2 https://www.abs.gov.au/articles/vitamin-d#edit-group-image--2 https://www.abs.gov.au/articles/vitamin-d#edit-group-image--...
- OutOfHere 11mo ago[flagged]
- supportengineer 11mo agoHow do you feel about vaccines and Tylenol?
- IAmBroom 11mo agoUncalled 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.
- layer8 11mo agoVitamin 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).
- slow_typist 11mo agoDogs can synthesise vitamin C…
- delecti 11mo agoAnd humans aren't dogs.
- deleted 11mo ago[deleted]
- anonlinc77 11mo agoCan 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.
- derbOac 11mo agoGlad 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/PIIS2213-8587(24)00348-6/fulltext https://www.thelancet.com/journals/landia/article/PIIS2213-8...
- pavon 11mo agoOne 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.
- colechristensen 11mo agoAnd 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)
- unionjack22 11mo agoVitamin 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.
- nickff 11mo agoWhile 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).
- djtango 11mo agoAmusing 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...
- lawlessone 11mo agoAre they that unpopular? Seem like a staple of an English Breakfast.
- djtango 11mo agoCouldn't quickly find any sources for the UK specifically but this should suffice https://pmc.ncbi.nlm.nih.gov/articles/PMC4632449/ https://pmc.ncbi.nlm.nih.gov/articles/PMC4632449/
- Theodores 11mo agoVitamin 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.
- canadiantim 11mo agoI wonder why we didn’t recommend vitamin D during Covid?
- dlcarrier 11mo agoOne 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 https://www.youtube.com/watch?v=oRkxH56LqCo Vitamin D therapy doesn't have such an effect.
- Supermancho 11mo agoThere 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 https://news.ycombinator.com/item?id=44705486 The Big Vitamin D Mistake
- stronglikedan 11mo agoBecause 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.
- mda 11mo agoUnfortunately 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.
- mwigdahl 11mo agoIf it's a scam, who's profiting? The pills are dirt cheap, generic, and over the counter.
- LocalPCGuy 11mo ago
- biscuits1 11mo ago"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.
- allisdust 11mo agoIt is a double blind study. what else do you want for confirmation ?
- ktktkgkhkke 11mo agoJust turn on an uv light for a few hours. Problem solved.
- Mistletoe 11mo agohttps://www.economist.com/science-and-technology/2025/09/17/the-health-benefits-of-sunlight-may-outweigh-the-risk-of-skin-cancer https://www.economist.com/science-and-technology/2025/09/17/...
- xwowsersx 11mo agoSupplementing 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
- johnisgood 11mo agoAnd K2. As for magnesium, I would go with magnesium glycinate or magnesium threonate.
- xwowsersx 11mo agoAbsolutely. And you're totally right about magnesium glycinate. That's what I take. I don't know why I said citrate.
- Etheryte 11mo agoAn 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.
- xwowsersx 11mo agoFor sure, you're essentially flying blind without bloodwork. I get a full panel at least 3x/year.
- Aldipower 11mo ago3-4 years ago this submission would be flagged in seconds just because of the word Vitamin D.
- CGMthrowaway 11mo agoReminder 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/ https://pmc.ncbi.nlm.nih.gov/articles/PMC5541280/
- lostdog 11mo agoI 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/ 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).
- turtlebro 11mo agoTake like 2g of Vitamin C. It's a lot stronger. Vitamin D is good too, but if anything you want to take C.
- elil17 11mo agoI 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.
- Liquix 11mo ago> typically without a meal any reason why? it's fat soluble and absorbs much better if taken with a meal.
- Etheryte 11mo agoUnfortunately 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.
- mrmuagi 11mo agoAnother thing I am curious about is time of day too -- I was told vitamin D/Multivitamins were better taken in the morning with food.
- cj 11mo agoIt 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)
- elil17 11mo agoBecause 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.
- mberning 11mo agoIn 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.
- pewpewp 11mo agoInteresting how your government did not mention Vitamin D during the COVID scare.
- kraig911 11mo agoI wonder if adding zinc on top of this would do.
- IAmBroom 11mo agoWould 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.
- boilerupnc 11mo agoA 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 https://www.science.org/doi/10.1126/science.adh7954 [2]: https://www.gutnow.com/medical-treatments/how-your-gut-microbiome-affects-vitamin-d-absorption/ https://www.gutnow.com/medical-treatments/how-your-gut-micro... [3]: https://journals.asm.org/doi/10.1128/spectrum.00083-24 https://journals.asm.org/doi/10.1128/spectrum.00083-24
- gwerbret 11mo agoHeh...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.
- roflmaostc 11mo agoIn 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/ 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/ https://ijmpr.in/editorial-board/
- roflmaostc 11mo agoThe first author is probably him: Dr. G Naresh (Asst. Prof.) https://aims.ac.in/general-medicine/ https://aims.ac.in/general-medicine/
- roncesvalles 11mo agoMy 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.
- hinkley 11mo agoI was pretty sure we already knew vitamin D deficits dampen the immune system.
- croes 11mo agoSo a vitamin deficit is bad for your health. Shocker.
- alphazard 11mo agoA 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.
- saretup 11mo agoThere can be hundreds of safe, possibly effective, and cheap interventions. Can’t try them all. Higher quality of evidence helps narrow it down.
- oldestofsports 11mo agoBreaking news! Water proven to clench thirst among those who are thirsty!
- lr4444lr 11mo agoDo 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.
- dynm 11mo agoThis 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 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.)
- patel011393 11mo agoTake 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.
- lisbbb 11mo agoWhat 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.
- astrostl 11mo agoI 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?
- yehosef 11mo agoI'm confused - Vit. D is essential for the immune system and most people are deficient - why isn't this obvious.