The survey in the article that assessed vitamin D deficiency was a bit odd:

>Because physical exams are performed in mobile vans in NHANES, data could not be collected in northern latitudes during the winter; instead data were collected in northern latitudes during summer and in southern latitudes in winter. To address this season-latitude aspect of the NHANES design, we stratified the sample into two seasonal subpopulations (winter/lower latitude and summer/higher latitude) before examining vitamin D status.

Yeah, I'm not surprised that the rates for vitamin D deficiency were low.

>Less than 1% of the winter/lower latitude subpopulation had vitamin D deficiency (25-OHD <17.5 nmol/L). However, the prevalence of vitamin D insufficiency in this group ranged from 1%–5% with 25-OHD <25 nmol/L /.../, even though the median latitude for this subsample (32°N) was considerably lower than the latitude at which vitamin D is not synthesized during winter months (∽42°N).

and the more northern latitude in summer:

>With the exception of elderly women, prevalence rates of vitamin D insufficiency were lower in the summer/higher latitude subpopulation (<1%–3% with 25-OHD <25 nmol/L)

Now imagine if you lived in northern Europe around the 60th parallel, where the sun doesn't get high enough in winter to produce vitamin D.

• qurren

  today at 8:18 PM

  Not to mention, northern latitudes get more sun that average in summer, and most northern countries have more reasonable working hours so people actually do go outside.

  • HPsquared

    today at 9:43 PM

    More hours of sun, but it's less intense.

• galleywest200

  today at 9:44 PM

  Could this be why evidence suggests that redheads synthesize Vitamin D more efficiently? Red hair is more prevalent at higher latitudes (I think).

  Can redheads produce Vitamin D in these darker conditions while others cannot do so effectively?

  https://www.sciencealert.com/evolution-favored-genes-linked-...

  • annzabelle

    today at 9:47 PM

    Pale skin in general helps synthesize Vitamin D. The less melanin you have the more you absorb, this is why lighter skin happens at northern latitudes. Darker skinned people are more likely to need to supplement it.

    • galleywest200

      today at 9:50 PM

      Makes sense, thanks for the reply and clarification!

Not in the field, but every time vitamin D studies come up I am reminded of the one that called out how current recommendations are based on faulty math (confusion on how to combine different sized studies confidence ranges ) and miss the mark significantly (and a lot of studies are based on those recommendations...)

https://pmc.ncbi.nlm.nih.gov/articles/PMC5541280/

• nostromo

  today at 9:19 PM

  To save people the click: the study says that the recommended vitamin D intake is much too low.

Has anyone done a RCT of D3+K2? K2 seems to be important in the absorption of D3. Another aspect that bothers me with these studies is that we’re simply supplementing the vitamin D, seemingly without measuring the change in blood levels. I took 2000IU (+K2) a day for many years in between testing my blood levels and still had <30ng/ml and had to go up to 5000IU/day. I’d like to see some further study.

• cj

  today at 8:11 PM

  K2 is also known to prevent problems with calcium build up which can happen if Vitamin D is dosed too high. I personally would never take Viramin D without K2 alongside it.

  • fridder

    today at 8:40 PM

    One problem: folks that are on blood thinners shouldn't supplement with vitamin k

    • moffkalast

      today at 9:32 PM

      If you are on blood thinners you probably shouldn't be taking common advice on anything tbf. Or diabetic. Or heavily allergic. Cause you will straight up die.

    • freehorse

      today at 9:33 PM

      only if the blood thinners taken are vitamin k antagonists (not all are)

  • throwaway613746

    today at 9:40 PM

    [dead]

• brandonb

  today at 8:09 PM

  TARGET-D is an in-progress study that supplements vitamin D based on blood levels (your idea).

  • nradov

    today at 8:47 PM

    I think that study is already concluded but the results haven't been published yet.

    https://clinicaltrials.gov/study/NCT02996721?tab=study

• odie5533

  today at 8:10 PM

  Were you taking hard tablets? And were you taking them with a fatty meal?

  Those are both very important. I take a Vitamin D + K2 softgel with a meal that has some fat in it.

  • aaronbrethorst

    today at 9:35 PM

    Costco sells D3+K2 softgels! Great price, of course.

    I started taking them at the recommendation of my podiatrist after I broke my foot last winter (third metatarsal fracture, specifically, ouch).

• nullc

  today at 7:52 PM

  > I took 2000IU (+K2) a day for many years in between testing my blood levels and still had <30ng/ml and had to go up to 5000IU/day.

  Likewise, 23ng/ml while taking 2000iu/day of dry vitamin-d.

  Switched to 5000iu +K2 in MCT oil, -- 8 months later I'm at 64ng/ml.

  • icedchai

    today at 10:07 PM

    I switched from 2000 to 5000iu about 8 years ago. My levels went up similar to yours, but I don't feel much different!

  • rbjorklin

    today at 9:45 PM

    Any noticeable difference how you feel health wise? Energy levels? Mood? Sleep quality?

• amelius

  today at 8:10 PM

  What I found was that I had to dissolve vit D under the tongue, not immediately swallow it.

This is a refreshingly balanced and honest analysis of Vitamin D studies.

The strongest evidence for Vitamin D is in people who are severely deficient. Bumping up to a normal range can provide some improvements.

The health influencers started noticing that the Vitamin D studies coming out weren't matching their original hype for Vitamin D, so many pivoted to trying to make claims that most people are severely deficient and just don't know it, which provides a convenient out to dismiss the studies that didn't pre-filter for people who were severely deficient. You can find waves of people on social media repeating the idea that almost everyone is Vitamin D deficient and encouraging high dose supplementation still.

Speaking to a doctor who runs Vitamin D labs as part of her annual physical screening process, she's now actually seeing more people who have excess Vitamin D than too little Vitamin D. Upon followup she discovers that patients have listened to a podcast about Vitamin D and started taking it regularly, unaware that they're pushing their levels into the range where it can start doing more harm than good.

Vitamin D is tricky because it lasts for a very long time in the body, which means steady-state supplementation can take a very long time to stabilize. I suggest anyone supplementing for a long time get a blood test, which can be ordered without your doctor if you can't get your doctor on board.

On another topic: Fish oil has also gone through a similar cycle of being hyped up based on early results, with higher powered follow on studies showing much less interesting results.

• sbayg

  today at 8:39 PM

  Baby aspirin was overdone too. Interestingly, the fish oil hype cycle has a much longer timeline if you consider the popularity of cod liver oil once upon a time.

  • nostromo

    today at 9:49 PM

    Cod liver oil wasn't hype, it was needed in norther climates to prevent rickets.

    It was taken for its Vitamin D, not for its omega 3s.

• dyauspitr

  today at 7:29 PM

  On a slight tangent, if people are unaware, you can pay for and get just about any lab test without a prescription in the United States.

  • jvican

    today at 7:37 PM

    Yes, and to be concrete, you can do so at economical prices at https://requestatest.com (it's a lifesaver in many occasions, I've used it 4 times with great success).

    • nostromo

      today at 9:51 PM

      And you can use a HSA or FSA to pay for it.

  • nomel

    today at 7:37 PM

    This is how I found my 10k IU of vitamin D a day, based on modern recommendations for indoor workers, that I modulate based on how much I'm outdoors, was perfectly on the mark!

    • Aurornis

      today at 8:07 PM

      Also an indoor worker. 10K IU daily would have put me far into hypervitaminosis D range.

      Make sure you test after a very long time, such as a year of steady supplementation. A lot of the excess Vitamin D cases were taking less than 10K IU daily.

      • nomel

        today at 9:22 PM

        > such as a year of steady supplementation.

        This is the entire issue. You get vitamin D from the sun. The concept of "steady supplementation" of vitamin D is not logical, unless your sun exposure is also steady, which is where the not-so-useful guidelines come from: some mean of some distribution of some skin tone of sun exposure, leaning on the "less" side of things, with current recommended values based on means from over 50 years ago.

        I would never take 10k steady, because I don't live in a cave!

    • lemonberry

      today at 7:43 PM

      This is the amount I shoot for in the winter - I live in New England - it's made a huge difference in my life. I'm totally open to it being placebo though and I don't care. I don't supplement with it during the summer.

  • Tangurena2

    today at 7:51 PM

    My PCP uses Quest Diagnostics and a vitamin d test is, I think, about $50. No fasting needed for it, nor prescription.

    • cj

      today at 8:58 PM

      Direct link to buy:

      https://www.questhealth.com/product/vitamin-d-test/17306M.ht...

      Definitely not the cheapest place to order the test from, but it will get the job done.

  • petesergeant

    today at 8:19 PM

    You can get most tests (although often not genetic) in many countries, with Canada being an outlier in forcing you to get a doctor’s note for just about everything.

• thaumasiotes

  today at 7:28 PM

  > The health influencers started noticing that the Vitamin D studies coming out weren't matching their original hype for Vitamin D, so many pivoted to trying to make claims that most people are severely deficient and just don't know it, which provides a convenient out

  Not really. It isn't possible to be severely deficient in vitamin D without knowing it. By definition, if you are severely deficient in vitamin D, you have rickets.

• anecd4t4

  today at 7:50 PM

  [dead]

It's arguable whether Vitamin D is really a vitamin or a hormone, see

https://pubmed.ncbi.nlm.nih.gov/33549285/

Look at the molecular structure

https://en.wikipedia.org/wiki/Vitamin_D

that's a freakin' steroid with one of the bonds in the rings deleted

https://en.wikipedia.org/wiki/Secosteroid

• brandonb

  today at 8:13 PM

  It's pretty well-established science now that vitamin D is a hormone, not a true vitamin. Vitamin D binds a nuclear receptor that regulates roughly 1,000 to 2,000 genes (5-10% of the human genome).

  The "Vitamin D" moniker has just stuck around since it was named in 1922.

  • infinite_spin

    today at 8:24 PM

    Yeah, it's just a holdover, the term "vitamin" originated from "vital amine", and vitamin D doesn't even have an amine group

    • raverbashing

      today at 8:38 PM

      Well neither does Vitamin C.

Even so, it still seems to be a small effect. The author mentions some studies looking at sunlight vs all cause mortality. These, and more recent studies [1] found much higher reductions in all cause mortality from sunlight exposure, of about 30%. It's thought that other factors may be behind this, such as NO production in the skin in response to UV [2].

[1] https://pubmed.ncbi.nlm.nih.gov/32918215/

[2] https://karger.com/bpu/article-abstract/41/1-3/130/328295/Su...

• Aerroon

  today at 7:57 PM

  Sunlight would likely get you all the "red light therapy" effects too.

> For a while there, many people thought vitamin D was magical

I never heard that in Germany. I only heard that if you use certain medications like cortisone that vitamin d could be problematic. Most doctors will give vitamin d supplements when prescribing cortisone, at least in Germany.

• holistio

  today at 9:19 PM

  Just two borders away, in Hungary, I've heard plenty of "magical vitamin D" tales. Tired? Take some D. Depressed? Take some D. Leg hurts? Take some D.

  I do take it in the winter, but I'm quite skeptical regarding the panacea hype.

I suspect that blood vitamin D is mainly a marker for how much outdoor exercise people are getting, and that it is the exercise rather than the D which is causal.

• written-beyond

  today at 7:26 PM

  My life changed after I got tested for vit D and started talking supplements. I was severely deficient. I am now sufficient and everything changed for me.

  • adamredwoods

    today at 10:04 PM

    I am deficient, too, and take supplements (rare liver disease).

    I wonder if taking mushrooms soaked in the sun improves absorption compared to supplements?

  • PierceJoy

    today at 10:08 PM

    How do you know the changes aren’t placebo?

  • heisenbit

    today at 7:59 PM

    In December by chance I put a pack of Vitamin D into my shopping basket. I did not think much, thought to take 1000IE but then decided that for the first week I take 3000 to catch up. Muscle pain went and control over eating improved. I did not expect any changes based on past experience with 1000 but this time I could not ignore it (age can play a role) and I stayed on 3000. Tests a month later showed I was just not deficient any-more. I continued on the regime and started having improvements in long running skin issues to the extent my dentist noticed. It may not be a miracle drug but one should not underestimate cumulative impact individual factors, age and lifestyle changes (less sun) that may change levels and demand.

  • wafflemaker

    today at 9:37 PM

    I used to take 4k IU + K² and think that I'm covered, since 4K units was a lot.

    I landed on just above deficient when tested.

    My wife was on kind of same regime, but didn't follow it very strictly. She was deficient, but not extremely.

    It was quite surprising, because I got warned when buying 4k unit tabs that they were quite strong and pharmacy clerk suggested taking less.

  • legitster

    today at 8:05 PM

    That doesn't undermine OP's point. Being deficient is unhealthy. But that doesn't mean an overabundance makes you healthier.

  • tweakimp

    today at 7:47 PM

    What exactly changed?

• nextos

  today at 7:27 PM

  Keep in mind vitamin D is really, among other things, an immune signaling molecule.

  So, we know the mechanism, and it's quite plausible that supplementation works.

  In other words, as an skeptic, I don't think it's just an epidemiological correlation.

• kccqzy

  today at 8:54 PM

  I also suspect that the frequency of outdoor exercise matters even if the total duration of outdoor exercise remains the same. Subjectively, I feel much healthier when doing thirty minutes of outdoor exercise six times a week, than when doing one hour of outdoor exercise three times a week. But then of course, all the causal effects could have been caused by a different factor (say dopamine release) than vitamin D.

• legitster

  today at 8:02 PM

  Ding ding ding.

  People who are drawing blood and trying to find some correlation between vitamin presence and health at this point are just practicing divination. The fact that it can be published in a scientific journal without any sort of RCT to back it up is palpably unscientific.

  The customers of these studies are the supplement companies looking for another product to sell.

• fragmede

  today at 7:22 PM

  But then why do we see improvements in people that get vitamin D + K2 supplements and not exercise?

  • amanaplanacanal

    today at 7:25 PM

    As the article mentions, we pretty much don't see improvements with supplementation.

    • rzz3

      today at 7:52 PM

      I don’t think there’s anything definitive. 400IU/day from one study is nothing if you’re deficient. 2000IU from another study is better, but even then we don’t seem to know much about absorption from these studies. For example, did it actually raise serum levels by 10ng/ml after a year, and how did THAT correlate to positive or negative health outcomes? K2 also seems to play an important symbiotic relationship with D, and seems notably absent from these studies.

    • criddell

      today at 7:47 PM

      From the article:

      > the balance of evidence tips pretty clearly in the direction that people with low-ish levels would be wise to supplement

  • warmedcookie

    today at 7:29 PM

    Yeah, I wish the article had brought Vitamin K2 into the mix since that seems trendy to pair with your D3 these days.

• smt88

  today at 7:48 PM

  Maybe this is true if you’re only considering white people. Brown people can spend a lot of time outdoors and still be deficient, especially if their ancestry is from much a much sunnier region or lifestyle than the one they’re currently living in.

  • petesergeant

    today at 8:23 PM

    Indeed: “Vitamin D deficiency in western dwelling South Asian populations: an unrecognised epidemic” … “27–60% of individuals, depending on season”

    https://pmc.ncbi.nlm.nih.gov/articles/PMC7663314/?utm_source...

  • kevin_thibedeau

    today at 8:38 PM

    It has never been established that darker people require the same amount of D as lighter. The supplement industry plays on these fearmongering to boost sales.

• mantas

  today at 7:35 PM

  It depends on one’s whereabouts and kind of exercise. Exercising in a gym or outside with all your skin covered won’t make much vitamin D.

In case the author is here, you can find the Garland & Garland (1980) article on sci-hub.

And if link is allowed https://sci-hub.ru/https://doi.org/10.1093/ije/9.3.227

Your body needs vitamins in order to form complex aminos to operate. But your body only needs to make so many of them - especially if you are an adult, not pregnant, or not suffering from a disease of some sort.

The very premise that loading up your body with "excess" vitamins beyond what you need is already pretty fraught. Building a house without enough lumber can lead to long term deficiency - but loading up a construction site with more materials than are needed shouldn't automatically be assumed to be good.

The reality is that the modern diet has already solved so many common nutrient deficiency diseases (pellagra and goiters were a shockingly common diseases 100 years ago) that maxing out on vitamin intake has become more of something like a speculative hobby than anything else.

• torstenvl

  today at 8:19 PM

  > loading up a construction site with more materials than are needed shouldn't automatically be assumed to be good

  It is almost universally recognized as good to do exactly that. It's better to have one planned extra trip to return excess materials (if they can't be used on the next job) than to have multiple unplanned trips when you unexpectedly run out of this or that.

• asdff

  today at 8:45 PM

  There would still be a ton of goiters if not for iodized salt, basically an obligatory vitamin intake. People had no good iodine source living inland where most anything they catch or grow is not going to have sufficient iodine no matter what it is they were eating.

  I'm not sure what the ancestral iodine source might have been. Fishing villages perhaps along the coast? Hard to say how much coast was relatively populated given challenges of shifting shorelines and archaeological efforts. You can still reproduce laden with a goiter however, and that is enough to keep chucking malnourished humans somewhere on earth.

  • OkayPhysicist

    today at 8:55 PM

    It takes a pretty extreme iodine deficiency to end up with goiters. In most environments, there's enough in the soil that eating local plants / animals that eat those plants supplies enough.

    The iodine deficiency issues that haunted the Swiss (and Appalachia) arose from people settling down from nomadic lifestyles, in mountainous regions that easily were leeched of iodine by rainfall, and then farming that already leeched soil until there wasn't any iodine left at all.

• PaulHoule

  today at 8:12 PM

  Most vitamins are a cofactor for enzymes like

  https://en.wikipedia.org/wiki/Thiamine#Biological_functions

  Vitamin D is not but rather it regulates calcium and phosphorous metabolism.

• gblargg

  today at 8:25 PM

  Depends on which vitamin as well. Some like vitamin B and C aren't retained, so excess is shed quickly.

• cute_boi

  today at 8:52 PM

  These days it is same with protein... Too much protein fads.

  • HerbManic

    today at 9:11 PM

    Yeah, you do need daily protein but for most people nowhere near as much as they are taking in.

    You see these protein bars and some of them basically have a full days worth of the stuff and that is before your other meals come in.

    There is the YouTube channel 'Subway takes' where people have about a minute to argue a point of view, usually very funny takes as well. There was one that was 'The Protein fad is basically an eating disorder for men', they aren't far off the mark with that.

    • legitster

      today at 9:27 PM

      >'The Protein fad is basically an eating disorder for men'

      This is such a bad take.

      The current protein fad isn't being driven by men. Bros have been hyping protein and keto for over a decade.

      The current "put protein in everything" fad was driven by women's social media, especially mom influencers. You're seeing the explosion in products women are more likely to shop for.

      My wife started buying protein products after getting a flood of Reels talking up its benefits for children and women's health.

  • legitster

    today at 9:29 PM

    I think the difference is that increasing protein intake does offset other worse eating habits. So it's not that you need the protein, but there's a small probability that it replaces calories from refined carbohydrates.

• UpsideDownRide

  today at 8:04 PM

  Vitamin D deficiency entered the chat. It's a relatively common issue in many countries.

  • legitster

    today at 8:07 PM

    That's fair, but it also exactly explains why there are weak positive effects of extra Vitamin D.

    There's a lot of unknowingly deficient people out there who get benefits from supplements. But the benefits are limited by the upper bound of the deficiency.

  • im3w1l

    today at 8:11 PM

    Two things to consider: The recommended levels are established based on "good enough for 95% of people". That means that quite a lot of people can get by with less than the recommendation. Furthermore, being deficient is not a binary. If you are just a little bit deficient you may have very mild symptoms.

Another more recent trial (TARGET-D) is showing a 52% reduction in heart attack risk: https://www.empirical.health/blog/vitamin-d-heart/

That trial used a dynamically-adjusted dosage of a vitamin D3 supplement, where dosing was set as to keep blood levels within a target range of 40–80 ng/mL. IMO part of the reason this trial is showing better results than the previous clinical trials of vitamin D supplementation quoted in the above article is that vitamin D has bad effects if too low and too high. Adjusting the dose dynamically to achieve an optimal range gets you the benefits without some of the negative effects.

Just because vitamin D supplements helps with rickets doesn't mean supplementation helps all the other things we seem to attribute to vitamin D.

I think a good hypothesis for the discrepancy regarding why people with "naturally" high levels of vitamin D fare better than those who do not has to do with how vitamin D is produced naturally.

If you take the vitamin orally it might help for rickets and a few other issues but if you take it naturally via sunlight you might actually be having other benefits that aren't properly measured today.

With the current state of fear surrounding sunlight I doubt people are getting enough to see benefits and all studies use oral supplements instead of time in sunshine.

I was taking 4000IU of Vitamin D daily along with 100 mcg Vitamin K-2 MK-7. My Vitamin D level was 60ng/ml. I've since dropped down to 3000IU per day. I go outside a lot but am either covered or using sunscreen since I sunburn easily.

• bethekidyouwant

  today at 9:49 PM

  Pretty sure if you’re burning easily then you are making vitamin D easily so just go in the sun but not so much that you burn. (which is i think common sense)

> Because physical exams are performed in mobile vans in NHANES, data could not be collected in northern latitudes during the winter

Why not?

• infinite_spin

  today at 8:28 PM

  Probably due to road conditions during the winter season. Imagine asking someone who isn't used to driving on icy roads to drive a large van full of equipment up through the Rockies

• today at 8:21 PM

I like this author but this post was only weakly intriguing.

More importantly, I'd like to know how long it takes to write a post like this.

Everything I write, I try to research and publish in under 2 weeks.

This post looks like it grew over time. I like that quality very much.

• dynm

  today at 8:37 PM

  > I'd like to know how long it takes to write a post like this.

  In this case, about three weeks.

People who say vitamin d isnt important should read about auld rickie...

This is great. I wonder if there's something like a patreon model where we could sponsor similar deep dives on other supplements?

For example, I've been supplementing with nicotinamide riboside for a few years now. I stop occasionally and when I do stiff and sore hands and knees return and I get more headaches.

I'd love to know if I'm deluding myself (placebo effect?) or there's good science that backs up my experience.

• js2

  today at 8:07 PM

  examine.com

  • criddell

    today at 8:52 PM

    Thanks!

    The results from examine.com for nicotinamide are interesting, but not as focused or concise (or usable) as the vitamin D information in this posting.

Medical doctor here. Please don't get health advice from hn comments. As a matter of fact, I advice against reading anything about health on hn, as the risks of dangerous misinformation far outweigh any useful information you might learn here.

• annzabelle

  today at 10:08 PM

  There was a thread that touched on lyme disease recently, and there were a ridiculous number of comments going down pseudoscientific rabbit holes about people who'd somehow gotten chronic lyme in places with no endemic lyme disease and that the only ways to fix this were chronic antibiotics and hyperthermia chambers.

  HN often suffers from the trait of people who are really bright in one area assuming that that means they are really knowledgeable in areas they don't know much about.

• kev009

  today at 9:31 PM

  Halp us docter

Just mildy exaggerated? Is this a joke article? If you don't achieve a suitable level, health will suffer immensely, even permanently. There are no ifs and buts. People who say otherwise work for the medical industrial complex and will get you killed.

Note that adequate magnesium is critical for proper vitamin D function, but the article doesn't document it.

• gblargg

  today at 8:30 PM

  Same for breathing oxygen, if you don't get it you'll die, but for most people oxygen supplementation would not be worth even knowing about.

  • OutOfHere

    today at 9:10 PM

    That's an absurd analogy. Vitamin D is a vitamin that is in large part derived from significant sunlight exposure. Vitamins are essential by definition. Sunlight exposure is highly insufficient by historical standards. This is why supplementation is absolutely necessary in almost everyone who is not a full time outdoor worker.

    In contrast, the air contains oxygen which is sufficient for most people with normal lung function.

• tonetheman

  today at 9:01 PM

  [dead]

I didn't see any mention of K2 (or missed it) - but a lot of D supplements combine with K2 as a "traffic cop" to keep calcium in bones and not arteries. I've not found a ton of evidence on this either, but seems to be a popular combination.

Ugh, more health pontificating from nonexperts. The blog is full of lame "hot takes." Blogspam, IMO.