The worthlessness of Vitamin D is mildly exaggerated

6/23/2026 at 8:08:53 PM

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.

by Aerroon

6/23/2026 at 8:18:57 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.

by qurren

6/23/2026 at 9:43:15 PM

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

by HPsquared

6/24/2026 at 9:50:47 AM

Is it really less intense? When I go out on a sunny day in Denmark it is murder. When I go out on a sunny day in Italy it's generally just overall warm.

At any rate another factor is that in the Northern regions it's my experience people do their best to soak up as much sun as possible.

by bryanrasmussen

6/24/2026 at 10:27:55 AM

I could believe that if you were near the coast.

I grew up in central Michigan and thought the same about the sun until I spent a few years in southern Arizona. The sun there feels like a heat lamp in summer. The low humidity makes the atmosphere absorb less energy. Although it feels like it's about 5 C cooler than it actually is because sweat evaporates so quickly, but once it gets to 43 C you actually just feel vaguely ill just going outside. Standing in the sun is just not something you do. It's a very unique experience to lick your lips and have your tongue feel cold.

Of course, neither of those were as bad as Houston in August. It was 38 C and 98 % relative humidity. And, I will point out, it had not rained. That's just what it's like. You walk outside and your glasses instantly fog up and you feel like you desperately need to shower.

by da_chicken

6/24/2026 at 3:24:04 PM

I live in Dallas and remember going hiking in Arizona and then getting in the car and the windows fogged up from sweat evaporating. Someone from a humid summer climate being outdoors in a dry summer climate has to really watch their water intake. It doesn't feel as hot because it's sucking all the moisture out of you and by the time you realize what's happening you're already not feeling so great. If you're 5 miles from water you're in a bad spot.

by chasd00

6/24/2026 at 10:06:47 AM

The sun is at a lower angle from the horizon at higher latitudes. It passes through more atmosphere, losing some UV, and also the surface irradiance on the ground (energy per unit land area) is lower.

by HPsquared

6/24/2026 at 11:30:01 AM

This. What I've learned for VitD conversion in the skin the sun needs to be more than 45° "high". Below that it's not much effective.

Those long summer evenings in northern Europe are thus not all that useful for VitD.

by flossly

6/24/2026 at 2:14:57 PM

I think it's because further north the Sun is at a lower angle in the sky. So high frequency waves like UV (needed for Vitamin D production) get filtered out by passing through more of the atmosphere.

Lower wavelengths like IR (heat) can more easily pass through the atmosphere. And since the Sun is lower in the sky, it hits more of your body. So you might feel more of the heat, while still getting less UV.

by wtetzner

6/24/2026 at 2:49:09 PM

Its about the angle yes, but the main thing is basically for every square unit of solar radiation gets projected onto a larger surface because of the angle- meaning radiation per unit area is lower. The secondary effect is that sunlight has to travel through more atmosphere, and gets scattered somewhat.

by jodleif

6/24/2026 at 10:55:01 AM

Sit in the sun for a bit closer to the equator. You'll feel it very quickly

by bluedino

6/23/2026 at 11:29:43 PM

Sure but i hide a lot more from the intense sun in spain then i do for the softer sun in sweden. In general i think it balances out quite well.

by calgoo

6/24/2026 at 4:11:39 AM

Does vitamin D synthesis require direct sunlight, or does it work with scattered light as well?

by fluoridation

6/24/2026 at 8:30:11 AM

Not really, it requires direct sunlight above 45 degree, so northern sweden for example gets plenty of sun in summer, but only for a very short time intense enough sun.

by lukan

6/23/2026 at 11:09:02 PM

The sun in northern countries in summer is less intense?

by codethief

6/24/2026 at 3:40:02 AM

Yeah, kinda.

I moved from Indiana to Norway - Trondheim, which is about in the middle of the length of Norway. During the summer, I can read outside at night even though the sun technically goes down for about 4 hours in June. It never gets darker than twilight. A few clouds means you might just have sunset all night. The sun does get surprisingly hot and very warming if we happen to have a sunny day. Jacket in the shade, short sleeves in the sun even though it is 18C/65F.

The reason for this is that the sun is at a low angle, so it hits more of your body than it does when the sun is overhead - like you'd get in Australia. This also means that while you need some sunscreen during the day - from about 10 to 5 - it doesn't burn as much. It is less intense in that way - but it just feels different.

During December, days are 4 hours of very weak light.

by Broken_Hippo

6/24/2026 at 5:44:33 AM

> The reason for this is that the sun is at a low angle, so it hits more of your body than it does when the sun is overhead - like you'd get in Australia. This also means that while you need some sunscreen during the day - from about 10 to 5 - it doesn't burn as much.

Not sure if I parse this correctly - I'd imagine you need more sunscreen at "low angles" due to more severe and longer exposure? Low angle -> more body surface area exposed directly at near-right angle to Sun -> more direct absorption -> more sunscreen needed?

by TeMPOraL

6/24/2026 at 10:21:28 AM

I’ve found the UV index forecasts to generally be a good metric, so try looking at those for various locations. The main factor here is that the lower the sun is from the horizon, the more its light will be absorbed by the atmosphere due to the longer path. The maximum altitude that the sun will ever reach is (90° – (latitude – 23.4°)), so at the 60°-ish of Scandinavia it’s rarely more than 50° in the sky. It’s a very noticeable difference even in the summer. In my experience (born in southern Italy, pale-average, currently living in Sweden) it’s almost impossible for me to get sunburn in daily life in Sweden even without sunscreen. Definitely not so further south.

by dgfl

6/24/2026 at 2:25:33 PM

> it’s almost impossible for me to get sunburn in daily life in Sweden even without sunscreen.

Um most Swedes, even with not-super-pale skin get a sunburn every june. Just being outside in the sunshine for 2-3 hours without any protection and they turn "kräftröd" as they say.

by teiferer

6/24/2026 at 8:32:51 AM

No, because the sun at low angles passes so much atmosphere, that filters most out.

The exposure angle of your body also has a effect, but much weaker.

by lukan

6/24/2026 at 3:28:55 PM

Today in Stockholm the UV index peaked at 6.3. And it is just a few days after the summer solstice, and the sky was largely clear today.

(Yet I can feel that I got slight sunburn being out for about 15 minutes today. So you still need to be careful.)

In winter the UV index might often peak at 1-2 on a clear day.

by VorpalWay

6/24/2026 at 6:07:43 AM

at lower angles the sun light needs to go through a much bigger "cross section" of atmosphere which greatly reduces its energy.

This is why noon sun is the most dangerous.

by Dansvidania

6/24/2026 at 5:29:51 AM

Huh now I know why I never liked living in Washington and Oregon, especially at higher altitudes. The sun always felt hotter.

by picofarad

6/24/2026 at 6:13:29 AM

I summer in California and winter in Washington for that reason!

by zippyman55

6/24/2026 at 7:38:15 AM

This low angle situation must have been experienced by every adult I imagine, its just about being outside before dawn and feeling how sun's warming effect on the body is much stronger than few hours ago even though air temperature itself might have been higher before.

Since it hits body more perpendicular its not rocket science, I realized this around age 10 myself and I am not the brightest in the pack.

by kakacik

6/24/2026 at 8:52:09 AM

I found this resource which shows that sun intensity in June in northern Europe is similar to that in sub-Saharan Africa (in June).

https://physics.weber.edu/schroeder/ua/EarthCirclesAndSunRay...

https://physics.weber.edu/schroeder/ua/SunAndSeasons.html

by ludicrousdispla

6/24/2026 at 10:13:49 AM

At the equator, the sun is highest at the equinoxes (March and September) and lowest at the solstices. Outside the tropics, the sun is highest at the summer solstice (June or December) and lowest at the winter solstice.

by HPsquared

6/24/2026 at 1:14:17 PM

Exactly at the equator the sun is directly overhead (90 degrees) at a single time point (close to 12 on depending on where you are within the time zone) every single day

The only thing that varies over the year is the path it takes to get there. At the solstices (summer/winter) the path curvature is maximal while t the equinoxes (spring/fall) it is a straight line.

by SJC_Hacker

6/24/2026 at 2:29:35 PM

Sorry that's just obviously false. It's only directly above you at the equinoxes, so twice a year. Otherwise it has traveled further north or south.

Before everything was an app, people had physical globes at home which could illustrate this very well.

by teiferer

6/23/2026 at 11:26:22 PM

Come to Australia during the summer and watch how quickly you burn outside without sunscreen.

by NoPicklez

6/24/2026 at 12:59:04 AM

Yes, it's crazy to consider how far north Earth's entire land mass is skewed. Australia is basically the southernmost landmass (apart from Tierra del fuego), yet it is located squarely under the Tropic of Capricorn; at the same distance north of the equator (Tropic of Cancer), you've merely reached Mexico, the Sahara desert, and the Himalayas.

by tremon

6/24/2026 at 2:31:53 PM

That'a not just the angle though, it's an issue with the ozone layer too, right?

by teiferer

6/24/2026 at 3:06:14 AM

For non-Australians, that's burn as in "burst into flames", not "your skin goes red". Go to somewhere like Cairns and you can hear people crackling as they walk down the street.

by pseudohadamard

6/24/2026 at 1:15:08 PM

Only for fair skinned individuals

by SJC_Hacker

6/24/2026 at 2:40:38 PM

Dark skin typically provides a protection equivalent to a ~10 SPF. Meaning some protection, but tons of the actual damaging UVB still going through.

by folkrav

6/24/2026 at 3:43:22 PM

which is like 2/3 of the Oz -- rampant skin cancer happens when you export the palest people on earth, anglo-irish-scots, to an unrelenting desert

by red-iron-pine

6/23/2026 at 11:20:02 PM

Yes, because it's lower in the sky so more of the UV in it gets absorbed by the atmosphere before reaching the ground.

For example, in Florida in the summer, the sun is close to directly overhead at noon. In Scandinavia in the summer, the sun is only about halfway up the sky from the horizon at noon.

by pdonis

6/24/2026 at 12:01:17 AM

less intense than in countries near equator, not less intense than winter

by xdavidliu

6/24/2026 at 6:34:49 AM

> 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.

Like... all of Finland? And most of Norway?

Both countries where the answer to "when does the sun rise?" can be "at the end of January".

by bostik

6/24/2026 at 10:22:34 AM

> data were collected in northern latitudes during summer and in southern latitudes in winter

And what were they doing for the other 9 months of the year?

by normie3000

6/23/2026 at 9:44:09 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-...

by galleywest200

6/23/2026 at 9:47:18 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.

by annzabelle

6/23/2026 at 10:24:46 PM

Darker skinned people in northern latitudes. Made worse for vegetarians like Ramanujan in England.

by bakul

6/24/2026 at 11:49:05 AM

"vegetarians" relevance?

by chrisweekly

6/24/2026 at 2:47:46 PM

Strict Vegetarians don’t eat eggs. No D vitamin fortified milk in his days. Many vegetarians don’t eat mushrooms, the only plant based source of vitamin D.

by bakul

6/24/2026 at 11:54:30 AM

Animal products are the primary natural dietary source of Vitamin D3

by niels8472

6/23/2026 at 9:50:50 PM

Makes sense, thanks for the reply and clarification!

by galleywest200

6/24/2026 at 1:28:21 PM

That sounds like a hypothesis that brown folks migrated north and evolved to be light as opposed to "light skinned peopled moved to the north". The latter is the historically accurate situation.

by economistbob

6/24/2026 at 9:57:12 AM

This is why you're supposed to fatten up in the summer. In nature, mammals fatten up all summer long, and fat soluable vitamins such as D, are stored in your fat.

As animals basically slowly starve over the winter, they consume their fat and also get some vitamin D back. It helps shore up the lack of sun in the winter.

by b112

6/24/2026 at 6:50:13 AM

I have made this comment on HN many times [0] now but: it's the goddamn sunlight.

Sunlight has many pathways in the body, and increased vitamin D levels are just one of those pathways. Swallowing one element of a many-element pathway cannot simulate the human synthesis of vitamin D! This should be obvious! Your car might not run because of bad needle bearings, but the solution is not to add them to the gas tank! First, you must always understand.

Sunlight / vitamin D is an especially aggravating issue because we have increasing amounts of research on how sun exposure improves general health. Sleep quality and regularity, mood, cancer incidence (as the article notes), eyesight, skin conditions, overall mortality, virtually every part of human health is improved by going outside. And when I say "improved" I mean improved to such a degree that it would blow 95% of prescribed drugs out of the water. See, for example, the Melanoma in Southern Sweden study where the highest sun exposure cohort had _half_ the all-cause mortality of the lowest group. Unfortunately the Western medical establishment is thoroughly captured by industry and you can't sell a pill that makes you go outside.

[0] https://news.ycombinator.com/item?id=42326209

by owenversteeg

6/24/2026 at 12:54:59 PM

I think science is just too granular to be a reliable input into wellness decision-making. It is too easy for interested parties to enable everyday people to confirmation bias their way into defying common sense.

Of what utility is the truth in decision-making if it is such a narrow truth that it might as well be a falsehood in practice?

Alcoholics talking endlessly about flavonoids, obese people insisting in polyunsaturated fat mayo, sedentary people that don't resistance train drinking soda with protein in it.

by randusername

6/24/2026 at 6:55:55 AM

Here in northern Europe, there just isn't enough sunlight to not become deficient, so a vitamin D supplement is a must.

by remix2000

6/24/2026 at 2:31:27 PM

Vitamin D is fat soluble, so it would be feasible to build up a supply in summer to last through winter. I've seen it theorized that a cyclical weight gain and loss tied to preindustrial seasonal food availability also plays a role.

by goda90

6/24/2026 at 2:49:15 PM

People tend to fatten up on winter and peaking at around winter solstice

Not sure how your plan should work?!

by spacington

6/24/2026 at 3:10:48 PM

Because of industrial food chains making that possible. Before we could refridgerate and ship food all over, most of your calories came from seasonal foods, and summer is usually more bountiful than winter.

by goda90

6/24/2026 at 8:47:01 AM

I looked up data from a calorie tracking app I used a while ago and I got just enough vitamin D. Main sources were fish, eggs and dairy products. However, I ate a lot and I'm quite sure in winter there will have been periods where I didn't get the recommend intake.

So if you live in a northern country and you don't like fish, I suppose it's quite a good idea to take a supplement.

Though as OP said, even if the sun isn't strong enough, there are plenty of benefits to going outside beside vitamin D.

by b-zee

6/24/2026 at 3:18:58 PM

If you gain weight during summer (so that excess vitamin D is stored in fat cells) and use body's stored fat in the winter (eat at a deficit, so that your stored fat, rich in vitamin D, is used), you need no supplementation. This is what all animals living in the region do.

by Rodmine

6/24/2026 at 3:57:51 PM

Unfortunately, sun exposure (specifically UV exposure) is heavily tied to skin cancers and aging. I haven't researched it myself, but my feeling is that, ultimately, there is a calculation where sun exposure / skin risk needs be balanced on your specific genetic makeup.

We really need to drill down into ethnic and racial boundaries to really make sense of how much sun exposure helps us.

by rirze

6/24/2026 at 11:26:25 AM

Which could be one of the reason people near the Mediterranean sea (for example in Italy) and tennis players do tend to live longer than average. Now of course there s probably more than one reason but those sure do enjoy time outside.

by TacticalCoder

6/23/2026 at 7:25:58 PM

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.

by Aurornis

6/24/2026 at 1:19:38 PM

You keep showing up under articles about vitamin D and keep telling that more people have excess than insufficient vitamin D levels without presenting any data whatsoever.

We're among plenty of inside-dwelling nerds here. Do the test. Don't listen to folks like the parent, don't let yourself be discouraged; check your blood level and act on it if necessary, it's fast and cheap. I even had a test done at my home, you can schedule that online these days! You're much more likely to be severely deficient than have it in excess (it's quite hard to get to toxic levels anyway, you'd need to be really irresponsible about it) and once you confirm that, supplementing can help you tremendously with plenty of mental issues you may be experiencing. It won't fix you up, but it can make it possible for you to fix yourself up in the first place. And if the test shows you have adequate levels already - good for you.

(and if you're too depressed to even arrange the test, it may make sense to start supplementing blindly - but don't exceed ~10K IU D3 daily and make sure to stop after 2-3 months tops. Hopefully at that point it'll be easier for you to finally do the test to know whether to continue or not; don't keep taking high doses blindly, toxicity is hard but not impossible to achieve and you really don't want to be suffering from it. You almost certainly won't reach it with 10K IU when starting from deficiency, but it you happened to be on the high side already at the start it could be dangerous when prolonged)

by seba_dos1

6/24/2026 at 5:33:34 AM

My family runs a blood analysis lab in Belgium for which I wrote some of the statistics gathering software.

The thresholds for 25-OH vitamin D: <20 ng/mL → deficient, 20–30 ng/mL → insufficient.

When I looked at all 1738 blood samples that had their Vitamin D tested between Feb 1, 2020 and Mar 13, 2020 (We were looking into the link between Vitamin D and COVID-19): The median (P50) was 20.1 ng/mL and the average was 22.4 ng/mL. Standard deviation: 11.24 ng/mL Half the samples were deficient, and the next 20% was insufficient.

Coming out of winter in Europe in a country with limited sunshine: most of the population is deficient in Vitamin D.

Histogram: https://files.catbox.moe/p785wx.png

by andruby

6/24/2026 at 6:02:22 AM

Worth noting all the three big studies mentioned in the article were on Americans.

by vintermann

6/24/2026 at 6:40:06 AM

The last of the three was done on Australians. Not that it changes your point, given the latitude of Australia.

by strken

6/24/2026 at 11:44:11 AM

The curve on your diagram makes me think that you've fitted a normal (Gaussian) curve to the data. By eye, the distribution looks a bit more like log-normal, and so if you're still working on the data, you might want to try that to see. Not that anything you've said or concluded seems wrong, though.

by bluenose69

6/24/2026 at 11:47:24 AM

The normal curve in the image is there for operators to visually check if the machine results are normal distributed or not. It's a "stencil", not data.

The software actually does a Lilliefors normality test which returns a big No on this data.

by andruby

6/24/2026 at 12:05:08 PM

Ah, thanks for the information.

by bluenose69

6/24/2026 at 11:00:36 AM

What do you think about the thresholds themselves? How often are they updated usually with new research?

by dizhn

6/24/2026 at 1:46:04 PM

Based on what I've seen while researching the topic for my own health purposes: the thresholds differ in various sources, but in general research appears to suggest that they may tend to err on the too low side rather than too high (there's quite a lot of headroom between what's often considered excessive and what's actually known to be toxic, while the lower end is much fuzzier).

by seba_dos1

6/24/2026 at 12:16:06 PM

I'm an engineer, not a clinical biologist or researcher. I have no idea.

On a personal level: I used to struggle with "winter dip". Taking Vitamin D supplements, as well as moving to South Africa, has both improved it a lot

by andruby

6/24/2026 at 7:35:00 AM

The Mediterranean diet itself has a lot of health benefits interrelated with the ones claimed about fish oil.

But just as a human experience, the first time I ate cod livers, it was hard to accept. Then I started spreading them on toast for breakfast, and realized that they were quite delicious, but very very much an acquired taste (and I eat almost everything).

As far as Vitamin D, there does seem to be a correlation between deficiency and severe coronavirus disease

https://www.mdpi.com/2075-1729/15/5/733

[edit] to say, I love chicken and cow liver, but it took awhile to get a taste for fish liver. Pork liver, however, is putrid. I don't think I could eat that again.

by noduerme

6/24/2026 at 1:10:10 PM

The Norwegian way to eat cod liver is “squished between two flatbread, mixed with boiled potato and also cod”.

Which is absolutely delicious, even for a kid; it’s one of the meals I still remember loving. You should try it!

by Filligree

6/24/2026 at 9:59:10 AM

Seemingly any decent way to tune in a steady-state supplementation involves multiple iterations of the "get blood test, adjust dosage, repeat" loop

On the other hand, when our body synthesizes Vitamin D itself it seems to regulate that process to prevent overdose. So I've just settled on supplementing in the winter based on my best estimate of the correct dosage, then let my body do its thing in the summer. No issues so far, and supplements have had a major impact on my fatigue/energy/depression levels in the winter

by wongarsu

6/23/2026 at 7:29:39 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.

by dyauspitr

6/23/2026 at 7:37:46 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).

by jvican

6/24/2026 at 3:00:05 AM

Other Quest resellers like https://goodlabs.com/ are way cheaper. Eg "Testosterone, Free (Direct) With Total Testosterone, LC/MS-MS" is $159 on that website vs $15 on goodlabs.

by NavinF

6/24/2026 at 5:35:01 AM

Nice! I didn't know about this company. Thanks for sharing. Has anyone tried and can they vouch for them?

by jvican

6/24/2026 at 6:57:34 PM

Yes I've used goodlabs. I paid them and they sent a prepaid lab order to Quest just like any other reseller. Also donated blood via goodlabs to get some basic labs for free, but that requires driving to SF. No donation sites in south bay

by NavinF

6/23/2026 at 9:51:47 PM

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

by nostromo

6/23/2026 at 7:37:46 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!

by nomel

6/23/2026 at 8:07:39 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.

by Aurornis

6/23/2026 at 9:22:01 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!

by nomel

6/23/2026 at 7:43:07 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.

by lemonberry

6/23/2026 at 7:51:30 PM

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

by Tangurena2

6/23/2026 at 8:58:43 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.

by cj

6/23/2026 at 8:19:31 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.

by petesergeant

6/24/2026 at 1:54:27 AM

Really terrible in Canada. If you don’t have a family physician (like everyone I know), good luck making it through triage at the walk-in clinic because you want a test to see your baseline values or proactively check for deficiency. The “hack” is you can pay a naturopath to order tests but the tests are not covered by public insurance in this case (actually pretty expensive IIRC).

by StayTrue

6/24/2026 at 4:48:54 AM

I’ve had good experiences with getmaple for random and quick doctors appts

by petesergeant

6/23/2026 at 8:39:24 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.

by sbayg

6/23/2026 at 9:49:38 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.

by nostromo

6/24/2026 at 12:39:05 AM

They used it for both and as a source of vitamin A and whatever other nutrients are in it. They used it for everything. There is an episode of I Love Lucy where a recipe for homemade baby formula is described which includes cod liver oil.

In a lot of things it was pretty good at what they used it for though, that does continue to be true.

by jrumbut

6/24/2026 at 1:57:08 AM

The moral of the story here is just to do bloodwork on a regular basis (absolute bare minimum once a year) and respond accordingly. I take some supplements like vitamin D, but I only take what is empirically measurable. If I can't quantitatively measure the outcome, then there is no value and it's a woo woo solution. This isn't always going to be the best advice, but a vast majority of times it will be.

by SOLAR_FIELDS

6/23/2026 at 7:28:11 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.

by thaumasiotes

6/23/2026 at 7:50:30 PM

[dead]

by anecd4t4

6/23/2026 at 11:45:47 PM

It's pretty safe to assume all hyped supplements are pointless. Being generally active and eating fruits/vegetables is like 80% of the work for being healthy.

> almost everyone is Vitamin D deficient

This was the red flag that made me realize it was BS early on. If everyone is deficient, then it must not be that important.

by yoyohello13

6/24/2026 at 1:06:08 AM

> If everyone is deficient, then it must not be that important.

Most people are overweight. Does that make being a healthy weight not that important?

by ChadNauseam

6/24/2026 at 5:11:29 AM

[dead]

by Lionga

6/24/2026 at 2:28:47 AM

most people can tolerate being overweight pretty well it seems

by cobalt

6/24/2026 at 9:49:14 AM

Not according to the public health literature. But, hey, don't let hard population data spoil what things "seem" to you.

Here are a few highly-cited articles to get you started:

https://link.springer.com/article/10.1186/1471-2458-9-88 https://www.nejm.org/doi/full/10.1056/NEJMoa1614362

by epihelix

6/24/2026 at 2:53:51 AM

For what definition of “tolerate”?

by monkpit

6/24/2026 at 2:32:06 AM

> Being generally active and eating fruits/vegetables is like 80% of the work for being healthy.

I suspect that a relatively low percentage of people in a solid number of wealthy countries meet these qualifications.

> If everyone is deficient, then it must not be that important.

This isn't sound logic. Something being common doesn't make it unimportant or less of a problem.

by Grombobulous

6/24/2026 at 12:19:06 AM

> Being generally active and eating fruits/vegetables is like 80% of the work for being healthy.

Except for the things that you get from sunlight, not diet.

> If everyone is deficient, then it must not be that important.

But nobody who lives in e.g. East Africa and spends a lot of time outdoors is deficient.

So it's actually pretty reasonable to say that a modern indoor lifestyle combined with long winters would truly lead most people in those regions to being deficient.

by crazygringo

6/24/2026 at 12:26:53 AM

If everyone is deficient, how would you even establish a baseline of what counts as deficient and excessive? The way they do that is they sample the population and look at the ranges of the values and maybe look at when comorbitity issues arise within those ranges. But “everyone is deficient in X” is easily dismissed hokum.

by vlovich123

6/24/2026 at 2:41:34 AM

Logically speaking, an affliction being extremely common or universal does not dismiss it as no longer being an affliction.

Many things about our society are extremely new compared to the conditions for which our bodies are evolved to be in.

by Grombobulous

6/24/2026 at 4:17:14 AM

I think you missed my point. vitamin D levels in and of themselves aren’t an affliction. The “correct” level is established by looking at what everyone else has and also by trying to look for comorbidities. But the comorbidities are often hard to tease out; about the only disease we know is rickets. Everything else is weakly correlational for vitamin D.

How do you think they define healthy levels of other hormones like testosterone and estrogen? They look at the range of levels for them, they look to see when they think diseases start, and they say those are correlated and you should adjust.

by vlovich123

6/24/2026 at 8:49:56 AM

>Everything else is weakly correlational for vitamin D.

All cause mortality is correlational for vitamin D. Various disease outbreaks (common cold, etc) and severity are correlational for vitamin D. etc We even know by which mechanisms so it's not like this is far fetched stuff where we're overlooking things.

This kind of stuff slaps you in the face if you live in the northern half of europe. To then think us now spending the majority of our waking hours indoors and the prevalence of those things and seasonal depression in winter when one leaves in the dark and comes home in the dark all has no effect....I think that's just hubris.

by modo_mario

6/24/2026 at 12:49:15 PM

Similarly, many things have issues that may not seem like issues at first. For instance most people are deficient in protein owing to simply not getting enough and a significant chunk of what they do get coming from sources with extremely low digestibility/DIAAS scores.

And somebody may not even realize this until they decide to start downing a few more chicken breasts per day and suddenly see their energy levels skyrocket, their hunger diminish, and so on. But if you surveyed them prior, they'd claim to feel perfectly normal.

Another one is testosterone which is extremely unfortunate because there's no remotely natural way to meaningfully regain significant amounts of it, but TRT is a life changing thing for many people who have low testosterone which in modern times is a huge chunk of all men and essentially all of them over a certain age.

by somenameforme

6/24/2026 at 12:33:15 AM

> is like 80% of the work for being healthy

I would suspect you're a man under 60.

I don't think your statement applies to the elderly (e.g. my mum needing D and Calcium for osteoporosis).

And I've seen many active healthy female friends under 60 actually need suppliments (I'm ignoring the stereotypical yoga worried well): plus pregnancy or health issues have an impact too.

But maybe I'm a victim of sampling bias since the men I know seem much less likely to see a doctor.

by robocat

6/24/2026 at 12:48:58 AM

I don’t want to get into an argument about health on the internet, it’s really a no win situation.

Although feeling bad, going to a doctor, getting labs, taking a calcium supplement is completely legitimate and a very different story from watching a YouTuber say ‘everyone is vitamin D deficient’ then going out a buying a bottle of supplements.

by yoyohello13

6/24/2026 at 12:31:18 AM

Pretty much the only one with a real consensus around it is creatine. And even that has debate around the right dose

by ewild

6/24/2026 at 12:52:59 PM

The interesting thing about creatine is that people's natural absorption varies dramatically. So some chunk of people will see basically nothing from creatine because their natural levels are already at saturation, whereas most will see relatively major benefits. I continue my 5g/day even when I'm not actively lifting.

by somenameforme

6/23/2026 at 8:59:42 PM

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/

by persedes

6/23/2026 at 9:19:13 PM

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

by nostromo

6/23/2026 at 10:24:50 PM

Honestly you don't even need to know the recommended number. In many countries you can get tested for free, and if that's not the case for you, getting tested usually costs in the ballpark of a box vitamin D supplements. Measure and only then supplement, then measure again later. You don't need to fly blind.

by Etheryte

6/23/2026 at 11:41:01 PM

A year's worth of daily 5000 IU (125 mcg) Vitamin D supplements costs approximately $15, so you could also just supplement.

by anamexis

6/24/2026 at 12:41:11 AM

Strangely the protective effects of vitamin d for heart disease appear NOT to be achieved through supplements. (Though the protective effects for cancer ARE)

I’m going to go out on a limb and guess that people who get outside a lot protect their health through both natural vitamin D from UV light exposure and cardiovascular exercise.

by tim-tday

6/24/2026 at 9:22:51 AM

This approach doesn't make much sense to me. Why supplement something when you don't even know that you need it? You could make the same argument about any and every supplement and eat the whole alphabet soup every day, but that's just putting extra strain on your body.

by Etheryte

6/24/2026 at 1:37:45 PM

Well, if a study finds that nearly everyone of your skin color at your latitude is deficient, you can make an educated guess.

by anamexis

6/24/2026 at 2:45:18 PM

[dead]

by Etheryte

6/24/2026 at 5:20:19 AM

This has come up several times before. It's not well cited. I read through it myself and even if the math is right, the application of the math seems incorrect.

The original data was a small number of studies with a small amount of old (1980s?) data that found a slope with so-so correlation.

The revised math finds a much smaller slope with what appears to be much worse fit to the same old data. The data was nearly horizontal before, but after the math changes it's much further away from 0.

The original study was making predictions near the data. The revision is doing massive extrapolation, far away from the range of what any of the studies tested.

I'm not a statistician, but it's not surprising to me that it's being ignored.

by rendaw

6/23/2026 at 7:44:26 PM

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.

by rzz3

6/23/2026 at 8:11:41 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.

by cj

6/23/2026 at 8:40:00 PM

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

by fridder

6/24/2026 at 1:26:57 AM

Vitamin k and k2 are not at all the same with respect to blood thinning

by anjel

6/23/2026 at 9:32:10 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.

by moffkalast

6/23/2026 at 9:33:07 PM

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

by freehorse

6/23/2026 at 9:40:45 PM

[dead]

by throwaway613746

6/23/2026 at 8:09:14 PM

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

by brandonb

6/23/2026 at 8:47:03 PM

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

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

by nradov

6/23/2026 at 8:10:27 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.

by odie5533

6/23/2026 at 9:35:25 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).

by aaronbrethorst

6/23/2026 at 7:52:02 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.

by nullc

6/23/2026 at 10:07:07 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!

by icedchai

6/23/2026 at 9:45:34 PM

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

by rbjorklin

6/23/2026 at 10:17:09 PM

Not the same person here, but a data point nonetheless. Before supplementing D3 I had a cold basically every year, sometimes twice a year. Since I brushed up my levels I average 1 cold in 6 years.

by _0ffh

6/24/2026 at 1:05:30 AM

Oddly, since the Covid time, I haven't caught a cold or flu once. I'm not sure it's the vaccines, the flu shots, or the less physical contacts on things overall. I still go to crowded places from time to time, like plane or train rides. May be the population in general have less cold or flu virus overall to go around.

by ww520

6/24/2026 at 5:29:22 AM

for me, i was so deficient that i would notice it the next morning. also probably not a placebo as the D supplement i am taking is not something my mind goes to 7 am pre coffee lol

by nicman23

6/24/2026 at 12:56:43 AM

Unfortunately too many other changes happened at the same time. I am enormously healthier now (in numerous measurable as well as subjective ways) but it may be that the D levels played no role.

by nullc

6/23/2026 at 8:10:43 PM

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

by amelius

6/24/2026 at 3:11:02 PM

Vitamin D is a biomarker of a process that happens in the body that is beneficial for longevity. This biomarker is created in response to receiving sunlight. The synthetic vitamin itself, does little, if anything, for your health. The process of receiving the sunlight is what benefits your health. This applies to a lot of other vitamin supplements as well.

So whilst you may be able to take a supplement to boost your vitamin D levels, the negative health effects of lack of sunlight are still going to occur.

by nullbio

6/24/2026 at 3:15:27 PM

Do you have any sources for this? Genuinely interested in reading more.

by redrove

6/24/2026 at 5:54:02 PM

I've recently run into and explored research explaining that natural sunlight stimulates energy production in mitochondria, resulting in an energizing and healing effect completely separate from vitamin D production.

I feel bad for posting this without references so here's one reference I could find right now:

> This study shows that longer wavelengths in sunlight are transmitted through the body. When these are presented via NIR LEDs in a laboratory-controlled environment at much lower energies, they again have the ability to be transmitted through the body and also are associated with improved visual function independent of ocular exposure. Hence, body penetration by longer wavelengths impacts systemically. Longer wavelengths improve mitochondrial membrane potential and ATP production and improve function in a species conserved pattern that can impact on mobility, visual function and cognition, particularly in ageing. In short lived animals they can extend average life span.

> Taken together, these data provide evidence of the importance of the full spectrum of sunlight for human health. They also highlight the potential dangers of the restricted spectra found in white LED lighting in the modern built environment that lacks longer wavelengths and whose output is generally restricted to around 400–650 nm. The absence of longer wavelengths from LED light sources may have implications for public health that should be addressed.

Source: https://www.nature.com/articles/s41598-025-09785-3#Sec5

by xolox

6/23/2026 at 8:09:59 PM

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

by PaulHoule

6/23/2026 at 8:13:27 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.

by brandonb

6/23/2026 at 8:24:45 PM

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

by infinite_spin

6/23/2026 at 8:38:46 PM

Well neither does Vitamin C.

by raverbashing

6/23/2026 at 10:48:47 PM

It is a cofactor though

https://en.wikipedia.org/wiki/Vitamin_C#Pharmacology

by PaulHoule

6/24/2026 at 8:46:19 AM

I think Vitamin D deficiency hype is driven by supplement sellers.

As someone who grew up in a European country where we don't get long summers, I suffered no demonstrable issues from the lack of sun nor did the many around me.

My family wasn't rich so food was reasonably nutritious but not perfectly balanced either.

Vitamin D supplements are sold widely, including in smaller supermarkets like Lidl and Aldi. And one imagines it all comes out of the same few factories.

There will be some who do need it, but not as many as are led to believe they do.

by khurs

6/24/2026 at 7:24:22 PM

a years supply of Vit D is like ~$30

you're telling me Big Vitamin is hustling the rubes that much?

the reason it is commonly hyped is because it is in fact reasonably common, and because the fix is cheap and has no real side effects unless you take comically massive doses

by red-iron-pine

6/24/2026 at 9:10:08 AM

As many other things, it depends on diet and lifestyle. I also live in the cold north, and generally, if you're fair-skinned, spend enough time in the sun and consume at least some products with natural or added vitamin D, you're usually good.

Having a balanced diet and enough time to spend in the sun isn't a given, though, and many struggle getting enough vitamin D without suppments.

by 2000UltraDeluxe

6/24/2026 at 9:52:02 AM

tell that to the 90% of belgians with deficiency

by nerbert

6/24/2026 at 9:25:14 AM

All I know is I used to have full on colds during winter in my 20s to early 30s, like every winter I would get two weeks of runny nose till the skin became red and irritated, sore and painful throat, coughing, etc. Since I take 25000 IU (D-Cure in Belgium) like 2-3 times a month during winter for the past 15+ years my cold last 2-3 days and symptoms are much more mild. For me the data is there.

by AltruisticGapHN

6/24/2026 at 9:35:40 AM

The problem is that you don't know what your situation would be like if you'd not taken Vitamin D. There are too many variables, generally -- e.g. in your early 20s and 30s you're likely socialising with many more people (so, more exposure chances), and you may also have young children (even worse disease vectors).

I'm similar to you in experience, btw, except that I don't believe correlation is causation. But as it won't do any harm, most of us don't regularly monitor our Vitamin D levels, and Vitamin D supplements are cheap -- it becomes a harmless form of Pascal's wager that I'm happy to keep making. Nothing to lose except a very, very tiny amount of money.

by epihelix

6/23/2026 at 7:18:14 PM

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...

by cpncrunch

6/23/2026 at 7:57:56 PM

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

by Aerroon

6/23/2026 at 7:54:56 PM

> 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.

by merb

6/23/2026 at 9:19:14 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.

by holistio

6/23/2026 at 7:21:21 PM

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.

by amanaplanacanal

6/23/2026 at 7:26:58 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.

by written-beyond

6/23/2026 at 7:59:23 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.

by heisenbit

6/24/2026 at 1:12:07 PM

I do think this is worth emphasising: the article only focuses on mortality. Not quality of life. Vitamin D makes me not feel like crap, it's cheap, and effectively zero risk. I'm not expecting it to make me live longer, I like that it makes me live better.

by regularfry

6/24/2026 at 11:03:03 AM

2 years ago i caught some repeated strep throat infection, repeated like 6-8 times - because my original general doctor said that with low CRP there is no way i have bacterial infection... before i found a doctor who finally did proper swab and ABTs - but i was so far gone that i got horrible headaches, muscle pain, stinging, absolute weakness... on top of that i cought covid and proper flu. Totally crazy, when they did mi vitamin D it was at 10% of minila recomended value. I god vit D and some immunity pills(pigs blood cells - this is questionable). I was slurping the vitamin D every day and in couple of weeks I was almost back to normal.

I have seen neurologists, imunologist, infection diseases specialist, everything is boreliosis qack and even somatic doctor...

Funny thing is before i got sick i spent 3 months on tenerife, so no reason for me to have low vit D. But it was probably depleted by immunity trying to fight the repeated infections.

so yeah, get your vitamin D checked if you feel weak, low on mood or anything out of zen

by kvgr

6/23/2026 at 9:37:56 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.

by wafflemaker

6/24/2026 at 8:22:46 AM

Have you looked into UVB lamps?

by isodude

6/24/2026 at 1:29:12 PM

Had a friend talking about them, but they seem to be prohibitively expensive. Do you have positive experience using such lamps?

I tend to have some eczema on my scalp that sun really helps with.

Maybe a lamp that costs the equivalent of a week of holidays in a warm place could be justified after all.

by wafflemaker

6/24/2026 at 3:21:23 PM

I don't have any experience myself but they do seem to be effective. Yeah, I think you'd have to compare it to a holiday, or how much time that would mean in a Solarium.

by isodude

6/23/2026 at 7:47:08 PM

What exactly changed?

by tweakimp

6/23/2026 at 10:04:27 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?

by adamredwoods

6/24/2026 at 6:05:18 PM

Make sure those mushrooms are prepared well though because as I understand it, the human digestive system has a hard time breaking down chitin cell walls, so without proper preparation, the mushrooms may pass through mostly undigested.

The point about letting the mushrooms soak up sunlight to boost their vitamin D content is totally true and absolutely fascinating though!

> When commonly consumed mushroom species are exposed to a source of ultraviolet (UV) radiation, such as sunlight or a UV lamp, they can generate nutritionally relevant amounts of vitamin D. The most common form of vitamin D in mushrooms is D2, with lesser amounts of vitamins D3 and D4, while vitamin D3 is the most common form in animal foods. Although the levels of vitamin D2 in UV-exposed mushrooms may decrease with storage and cooking, if they are consumed before the ‘best-before’ date, vitamin D2 level is likely to remain above 10 μg/100 g fresh weight, which is higher than the level in most vitamin D-containing foods and similar to the daily requirement of vitamin D recommended internationally.

Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC6213178/

by xolox

6/23/2026 at 8:05:41 PM

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

by legitster

6/23/2026 at 10:08:52 PM

How do you know the changes aren’t placebo?

by PierceJoy

6/24/2026 at 6:28:55 AM

Because I was suicidal, had extreme mood swings and all of the muscle pain and instability.

I didn't even know about vit D, didn't research it. I just got a panel done to get an idea of what's going on with me and discovered I was severely deficient on vit D

by written-beyond

6/23/2026 at 7:27:54 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.

by nextos

6/24/2026 at 12:39:54 AM

Bingo. Obviously being deficient is bad, but the reason supplementation seems unimpressive is this is one of those proxies for healthy lifestyle. Kinda like how grip strength is correlated with longevity but banging out tons of hand gripper sets isn’t going to do much for you health.

by systemsweird

6/23/2026 at 8:54:36 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.

by kccqzy

6/23/2026 at 7:48:09 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.

by smt88

6/23/2026 at 8:23:10 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...

by petesergeant

6/23/2026 at 8:38:14 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.

by kevin_thibedeau

6/23/2026 at 7:22:58 PM

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

by fragmede

6/23/2026 at 7:25:25 PM

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

by amanaplanacanal

6/23/2026 at 7:52:42 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.

by rzz3

6/23/2026 at 11:52:07 PM

if supplements don't absorb and therefore don't affect health, there's no reason to take them.

by adgjlsfhk1

6/24/2026 at 12:21:07 AM

You missed the K2 part of his comment though. Both my mother and I have chronically tested incredibly low for vitmain D, both always taken supplements, both never had improvement. A couple years ago, my mom texted me saying she tried a D3+K2 supplement and for the first time in her life tested in range for vitamin D on her panel. I was skeptical but tried it, and have tested in normal range since.

by grep_name

6/23/2026 at 7:47:44 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

by criddell

6/23/2026 at 7:29:57 PM

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

by warmedcookie

6/23/2026 at 7:35:20 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.

by mantas

6/23/2026 at 8:02:38 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.

by legitster

6/23/2026 at 11:12:15 PM

I experimented with D3 supplementation up to almost a decade ago. I made some HN comments about it [2018]:

https://news.ycombinator.com/item?id=17638508

I ultimately stopped it because it seemed to cause lower back aches. (Pretty sure, bone/muscle not kidney!) Every time I went on the D3, my back would start to hurt. That repeated several times, enough to suspect a pattern.

The cause may be similar to the itchy, tingling teeth.

According to this fascinating paper, Vitamin D can actually trigger the leaching of calcium out of bones, into circulation:

https://pmc.ncbi.nlm.nih.gov/articles/PMC8147670/

After the abstract, find the section heading "Vitamin D mobilizes calcium from calcified bone".

But that is in very high, pharmacological doses. Not your 5000 UI per day.

by kazinator

6/24/2026 at 1:31:45 AM

Not medical advice.

You probably need to take vitamin d3 with k2 to avoid the calcium issues.

Edited to add link https://pmc.ncbi.nlm.nih.gov/articles/PMC5613455/

by dashmeet

6/24/2026 at 4:33:43 PM

Early into the Covid pandemic, there was talk that vitamin D had some protective effect. Did this ever pan out into any kind of recommendation supported by evidence ?

by euroderf

6/24/2026 at 5:03:25 PM

https://pmc.ncbi.nlm.nih.gov/articles/PMC8541492/

by stevedt

6/23/2026 at 7:37:01 PM

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.

by brandonb

6/24/2026 at 9:31:32 AM

That blood level matches what the parent article cites as typical for Africans who were still eating their traditional food, and which is higher than typical for the industrialized countries.

by adrian_b

6/23/2026 at 7:51:37 PM

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.

by legitster

6/23/2026 at 8:19:54 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.

by torstenvl

6/24/2026 at 12:42:03 AM

You mean my DIY projects that result in a dozen trips to Home Depot aren’t optimal :)

by systemsweird

6/23/2026 at 10:10:18 PM

Definitely. I ordered material to replace the balusters on our shared family cabin with horizontal stainless steel cable deck rails and ordered 5-10% extra for all of the various fittings, cable, as well as a backup swage tool.

One of my uncles asked why I’m budgeting for an extra $150 of material we won’t need. I asked him how much it would cost to get us all up here for another weekend to finish if we needed extra parts. The answer was “more than $150” and he understood.

It’s even more crucial to keep enough material on the jobsite when you’re running a project and paying $140 an hour for an electrician.

by quickthrowman

6/23/2026 at 8:12:10 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.

by PaulHoule

6/24/2026 at 8:51:26 AM

While there is no doubt that excess vitamin intakes are useless or even harmful, the problem is that for most vitamins there is a great uncertainty about which are the optimum daily doses, because the controlled experiments that would be needed to determine those doses would be rightly deemed as unethical.

Therefore, since we only have some weak circumstantial evidence, debates about how much vitamin D is good, and the same about other vitamins, will continue. As long as the uncertainty persists, it is safer to ingest somewhat higher doses of vitamins than those recommended, but not many times higher.

The conclusions of the article were that high amounts of vitamin D have been shown to be correlated with good health outcomes, but the supplementation studies could not reproduce the same outcomes, so it remains mysterious what factor was associated with vitamin D in the studies with positive effects and whether vitamin D itself had any role or its presence was just a coincidence.

by adrian_b

6/23/2026 at 8:45:06 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.

by asdff

6/23/2026 at 8:55:51 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.

by OkayPhysicist

6/23/2026 at 8:25:31 PM

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

by gblargg

6/23/2026 at 8:04:42 PM

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

by UpsideDownRide

6/23/2026 at 8:07:34 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.

by legitster

6/23/2026 at 8:11:46 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.

by im3w1l

6/23/2026 at 8:52:56 PM

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

by cute_boi

6/23/2026 at 9:29:40 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.

by legitster

6/23/2026 at 9:11:16 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.

by HerbManic

6/24/2026 at 6:50:41 AM

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

I don't know, USADA is about as conservative as it gets and they certainly recommend a shitload of protein for for individuals trying to maximize muscle protein synthesis https://www.usada.org/spirit-of-sport/when-consume-protein-m...

>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.

For a 100kg man that would be like 220 grams of protein, must be one big protein bar.

OTOH, at least your username fits ;)

by l23k4

6/23/2026 at 9:27:50 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.

by legitster

6/23/2026 at 11:58:10 PM

    > Too much protein

Is there really a scientific consensus about "too much protein"? As I understand, the bit about "stresses your kidneys" has been disproven.

by throwaway2037

6/24/2026 at 9:11:16 AM

Too much protein can definitely kill you, or at least make you ill, as discovered by the Europeans who explored the northern parts of America and who had initially tried to live from the meat of hunted animals, until they learned from the natives that they must eat enough fat besides the lean meat, in order to survive (most wild animals have little fat, except the bone marrow, which must be extracted).

However, too much protein is a lot, much more than most people will try to eat in normal conditions, because an important advantage of protein is that it is satiating, i.e. when you eat enough protein it is easy to eat less food and more seldom, without feeling hunger.

For example, I eat 2 meals per day, in the morning and in the evening, of about 800 to 1000 kcal each. If I ate more, I would gain weight rapidly.

When I was eating any kind of industrially-processed food, I could not eat so little, because I became hungry quickly. Now I eat only food that I prepare myself, from raw ingredients. In order to avoid hunger, the content of protein and fat is very important. Typically, each of my 2 meals includes 40 to 60 g of protein and 20 to 30 g of vegetable oil. This ensures that I will not be hungry all day.

by adrian_b

6/24/2026 at 12:39:13 PM

> Too much protein can definitely kill you, or at least make you ill, as discovered by the Europeans who explored the northern parts of America and who had initially tried to live from the meat of hunted animals, until they learned from the natives that they must eat enough fat besides the lean meat, in order to survive (most wild animals have little fat, except the bone marrow, which must be extracted).

That's an issue of too little fat, not too much protein. The question is whether, when your other nutritional needs are being met, an excess of protein is an issue.

by monadgonad

6/24/2026 at 2:57:39 PM

No, it was too much protein, not too little fat, because they had to eat a lot of meat from hunting to provide enough calories, as they did not carry with them enough food containing starch and/or fat that could provide calories from other sources than protein.

It does not matter if most of the calories (i.e. more than two thirds) are provided by carbohydrates or by fat, as long as they are not provided by protein.

Fat was the solution for living far in the north because they did not have plant cultures that could provide carbohydrates.

Both the amount of fat and the amount of carbohydrates eaten in a day can vary in a very wide range without causing health problems, while the protein intake must be in a relatively narrow range to avoid problems. When eating fat with the right composition, i.e. from sources rich in essential fatty acids and in fat-soluble vitamins, something like at most 40 grams per day should be enough, so it is unlikely for someone to suffer from eating too little fat.

by adrian_b

6/24/2026 at 5:55:30 PM

Do you have any sources for this? I have also heard of rabbit starvation many times over the years, and it has always been in the context of too taking in too little fat -- essential fatty acids -- as well, due to the extreme leanness of the meat.

by Remnant44

6/24/2026 at 6:48:14 AM

I don't understand why literally everyone I know are diagnosed with Vitamin D Deficiency. Even living in sunny California. Wasn't human biology adapted for it in the last 40k years? I understand we spend more time indoors, but literally everyone?

by deepsun

6/24/2026 at 7:48:13 AM

We evolved to be in the sun for much of the day. We no longer do that. Many of us barely go outside at all anymore. Light skin is an evolutionary adaptation to mitigate the issues related to this in higher latitudes, but it's not match for modern indoor lifestyles.

by Gareth321

6/24/2026 at 7:11:59 AM

I started to take VitD on a whim and my mood and energy sure improved. Also I feel like I get sick less often. 3 friends whom I recommended VitD told me the same. Living in northern germany. YMMV.

by Imanari

6/24/2026 at 3:13:53 PM

Placebo is a strong thing. Unless you're actually getting more sunlight, it's doing nothing for you.

by nullbio

6/24/2026 at 6:32:57 PM

I'll take it ;)

by Imanari

6/24/2026 at 12:20:24 AM

Thousands of words and no mention of the obvious thing - testing whether sun exposure is beneficial or harmful.

The article opens with the observation that southern states had lower cancer rates due to solar irradiance. But then we intervene by taking pills. Why not try to absorb through the skin, even if it means something like a tanning bed?

by zhivota

6/24/2026 at 2:30:09 AM

There are many nuances and people seem bad at understanding those. Too many are getting their information from "health influencers" and 30 second videos, which is why we seem to bounce between the two extremes of "everyone should take Vitamin D!" and "Vitamin D is overrated!".

Australia has tried to explain sun safety here, taking into account that Vitamin D is best obtained from sunlight:

https://www.cancer.org.au/cancer-information/causes-and-prev...

by jerlam

6/24/2026 at 12:47:36 AM

Yep, it's sunlight.

Nobody will run that trial though because we've spent decades telling people the sun is dangerous and gives you cancer (both things can be true of course). Putting people in the sun every day would not pass ethics tests.

Also you cannot sell sunlight.

by chr15m

6/24/2026 at 8:05:50 AM

> Also you cannot sell sunlight.

Don't give them ideas.

by waysa

6/24/2026 at 4:42:34 AM

I have HIV and am under treatment using medication, I have found D3 and K2 helps alleviate some of the side effects of the medication; largely my mood. Which makes a lot of sense because my immunity system is in constant daily activity.

However, I need to get more sunlight; I just don't think supplementation is the same as being in the sun. When I was homeless I never had these mood issues, but that's complicated, living day-to-day & meal-by-meal puts you survival mode so nothing is really past the hour.

All anecdotal, duh.

by lonelyrock42

6/23/2026 at 9:33:47 PM

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

by jmhammond

6/23/2026 at 11:28:24 PM

I expect the author is aware of that: where do you think he got the graph from if there's only 'gated copies'? But Sci-Hub links are unstable even if you don't mind linking them.

by gwern

6/24/2026 at 3:31:28 AM

Linking to sci-hub for a known blogger may lead to undesired legal consequences in case the journal copyright mafia decides to make an legal example of you.

by elzbardico

6/23/2026 at 11:27:18 PM

I was told that there are lots of latitudes in North America where the sun is at too low an angle for your skin to make vitamin D for large parts of the year so you should take it during those times and then you should be fine during the summer if you get outside enough.

by green_wheel

6/23/2026 at 10:10:53 PM

The charts showing vitamin D not helping, but also slightly hurting make the topic more relevant. The title is almost too flippant of the conclusions which is don't just take more than necessary,because it's likely to actively cause harm not just slightly increase your vitamin D.

by skyberrys

6/24/2026 at 11:48:42 AM

> and it will still tell your bones to scavenge calcium... So the body scavenges a lot of calcium from your bones...

Bones take calcium from bones? Net effect 0 then?

by bcjdjsndon

6/24/2026 at 3:07:17 PM

Obviously that was an incorrect phrasing.

The concentration of calcium ions in the extracellular water and in blood is always kept approximately constant.

The bones are a reservoir of calcium in solid form, so whenever the concentration of calcium ions in the extracellular water drops the bones release calcium ions and whenever that concentration increases the bones retain calcium ions.

This takes care of short term fluctuations. In order to also keep the amount of calcium stored in the bones approximately constant, the gut will try to absorb more calcium from the food when it is insufficient and the kidneys will excrete the excess, when it is too much.

by adrian_b

6/23/2026 at 8:15:12 PM

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.

by xutopia

6/23/2026 at 10:21:48 PM

Leaving out skin colour from the conversations while mentioning 'randomized trials' and 'seasonal subpopulations' is problematic. Vitamin D production is highly tied to skin colour (melanin levels).

by whycome

6/23/2026 at 7:19:02 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.

by nilirl

6/23/2026 at 8:37:18 PM

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

In this case, about three weeks.

by dynm

6/24/2026 at 1:44:39 PM

I think taking a supplement every day is a good idea. I used to suffer from low vitamin D levels constantly until I started taking a daily vitamin D tablet.

by rizsyed1

6/23/2026 at 8:19:11 PM

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

Why not?

by ninalanyon

6/23/2026 at 8:28:35 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

by infinite_spin

6/23/2026 at 10:31:31 PM

They plow the mountain passes in the winter time in at least Montana and Idaho. I'd be very surprised if they don't in Colorado or Utah.

by floxy

6/24/2026 at 1:29:09 AM

They do, however the roads are, potentially icy, certainly after a storm, which means that you can't measure consistently, even if you're trying because some days the roads will be impassable.

If someone's not used to driving in snow, it'll be even worse. You should not let them drive if there's snow/ice expected in the next day; or the roads haven't been cleared yet. As someone who grew up in Minnesota, I can tell you that yes, we are better at driving in snow than people down south. However, we go in the ditch a lot anyway.

by bluGill

6/24/2026 at 7:55:39 AM

I rather liked his writing style - very easy to follow. He could have a future as a science communicator.

by tigerquoll

6/24/2026 at 10:32:43 AM

He is a professor of biostatistics at NYU

by fearnot

6/24/2026 at 4:06:00 AM

I was told I was Vitamin D deficient and accidentally over indexed on supplements and got quite sick. Some of the dosages on OTC are ridiculously high

by joehabeebs

6/24/2026 at 4:19:48 AM

A different personal experience. I had Vit D deficiency. Started on 2000IU per day and was still deficient after months. Then started on 5000IU per day, initially daily but now every other day or so. My last test was in the middle of the "normal" range. I have been taking VitD for 4 years or so. A lot of my symptoms like tiredness, sleepiness etc have improved since then.

I asked my immediate family members to do a test as well. Male/female, young old, across states and even countries. All of them except my mother had low Vit D levels. My mother regularly supplements as its recommended for bone loss prevention in that age.

by toxicdevil

6/23/2026 at 8:58:46 PM

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.

by vondur

6/23/2026 at 9:49:44 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)

by bethekidyouwant

6/24/2026 at 5:50:50 AM

Vice versa, the exaggeration of vitamin D is mildly worthless. Some need supplements, some don't.

by dippogriff

6/24/2026 at 1:39:59 PM

methylcobalamin B-12 plus Vitamin D3 is the preferred form.

Skip the D2 vitamin.

by egberts1

6/24/2026 at 12:50:11 PM

Thousands of words and no references list. Lame. Makes me suspect a piece written a bot. I have to dismiss almost all of it since there is no way to fact check and the article is filled with those asides that the bots put in there. The asides I refer to are the "are you still with me" and other psuedo-in-your-face punchy nonsense. Half the articles on the internet think I want backfill and history and punchy check-ins rather than the direct information that I used to scan through and obtain in about twenty seconds, but somehow those brand new AI slop sites are the top results on all engines (corruption since they sell services to generate those pages).

Lame. It started like enjoying an encyclopedia and ended like getting my face punched by a narcissistic robot who might have lied about facts and gave no way to spot check except redoing the entire article again myself from scratch. A novella on biophysics and no works cited?

Reading 7k words on biophysics with supposed data and science facts and getting hit with dozens of self reference footnotes instead of external citations is offensive to my intelligence.

I do not have the karma for the downvote button so I shall simply leave this.

Vitamin D is rat poison. The stuff they use in randomly controlled trials is not the stuff your body makes on its own. Too much sun and skin produced vitamin will not kill you. Too much rat poison will.

Real human research per the Material Safety Data Sheets with zero slop:

https://chemtrails.substack.com/p/vitamin-d-is-rat-poison-th...

by economistbob

6/23/2026 at 10:32:11 PM

Probably heavily depends on the country/region, but here in Germany it is basically the norm to be Vitamin D deficient. Like, half of the population have a deficiency when there is some sun and basically everyone has a deficiency for months during fall/winter/spring. So I have to laugh when I read "taking vitamin D does nothing unless you’re severely deficient". Yeah like, but that's most people in many countries lmao

by d2kx

6/23/2026 at 8:07:12 PM

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

by Johnyjohnson123

6/23/2026 at 7:53:52 PM

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.

by criddell

6/23/2026 at 8:07:48 PM

examine.com

by js2

6/23/2026 at 8:52:35 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.

by criddell

6/24/2026 at 10:31:09 AM

Again, dynomight proves he's better than us.

by fearnot

6/23/2026 at 10:38:18 PM

Have a loved one that has extremely low vitamin D issues. Takes ergocalciferol from time to time and it is pretty useful in my opinion.

by rhipitr

6/24/2026 at 2:03:25 PM

the Vitamin D RDA is too low at 800iu

but taking more than 2000iu per day is not just pointless but dangerous without blood testing

Vitamin D won't cure anything once there is a disease or illness

but it does show some preventative benefits

whole lotta people on Reddit do have blood tests showing it's way too low but those of course are the loudest voices

by ck2

6/23/2026 at 7:33:26 PM

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.

by fred_is_fred

6/23/2026 at 8:50:13 PM

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.

by atahanacar

6/23/2026 at 11:40:08 PM

Principal Armchair Commander here. I second this. That said I also avoid health advice from professionals. I have too often found their incentives to be in conflict with my well being. I just do my own research and ignore everyone, especially AI.

by Bender

6/24/2026 at 12:17:44 AM

I assume you are American? I find it sad that a doctor has any incentive other than providing their patients with the best care possible.

by atahanacar

6/24/2026 at 12:24:43 AM

I assume you are American?

Was it that obvious? It would be cool if I could have a theme song. [1] and yeah I don't know how to fix the US health care system.

[1] - https://www.youtube.com/watch?v=BVkTmnJkAN8&list=PLxUfU-CW9j...

by Bender

6/23/2026 at 10:08:22 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.

by annzabelle

6/24/2026 at 12:23:33 AM

That is relatively benign compared to what I've seen before. I normally refrain from repeating misinformation, even for debunking it but I will make an exception (or two). I've seen comments ranging from "salt intake doesn't increase blood pressure because you pee what you don't need" to "blood glucose levels aren't good for diagnosing diabetes".

Edit: OK, that's not really a "range". I have no idea why I phrased it like that. Both are very dangerous statements that can be life threatening if the wrong person believes it. I just hope that comment didn't cause any diabetic ketoacidosis cases.

by atahanacar

6/24/2026 at 12:26:19 AM

It’s always great when years of medical and scientific studies are instantly debunked by HN’s top JavaScript developers. One wonders why we even bother having research universities.

by acheron

6/24/2026 at 12:27:28 AM

Do you think people seeking medical advice from HN comments might be related to their disatisfaction from the suppor they receive from medical clinicians?

by cup

6/24/2026 at 12:35:52 AM

Yes and no. Some are just way overconfident in their knowledge of medicine and human body, while it is miniscule compared to the average physician's. Medicine is a field much larger than people realize. It is easy to think you know a lot when you don't even know how much you are missing.

Having a reason doesn't make it any less dangerous though.

by atahanacar

6/24/2026 at 12:20:09 PM

I can't fully agree with avoiding the topic altogether. Yes, people need to be careful, but building real knowledge in complex subjects like health generally requires engaging continuously (same as in Computer science) with research and studies (and learning to evaluate them critically) AND gathering people' opinions and perspectives (very important, after all, the experience of an MD grows over time because of reports of side-effects from your own patient, which is close), rather than shutting out discussion entirely, even for yourself who is already an MD. Also not everyone had the opportunity or desire to study medicine formally but still want a chance to be able to understand it in greater depth, and one great way to learn is to read a ton.

We can also relate that some drugs (albeit most are illegal but whatever, it doesn't invalidate them) from recreational to bodybuilding drugs are practically only massively "studied" by the bro-science community and many topic about harm reduction and so-on stems from there, enormous amount of people have started getting interested into health, supplements... due to reading about it randomly from people.

Although, in practice, you are partially right, it also does damage because many people will just take it as face value and just don't have enough expertise yet to do a proper reasoning around some takes and might not check if it's factual.

by pixel_popping

6/23/2026 at 9:31:32 PM

Halp us docter

by kev009

6/23/2026 at 10:11:16 PM

Vitamin D is a lifesaver for me. I'm severely deficient, and if I don't take about 10,000 IU a day, I seem to get colds every five minutes.

by innocentoldguy

6/24/2026 at 3:14:51 PM

Have you tried going outside? Spend 15 minutes in the sun every day. It's not really that hard.

by nullbio

6/24/2026 at 12:47:48 PM

Quod abundat non nocet

by voxleone

6/24/2026 at 4:27:56 AM

What if rickets is actually a variant of polio, and vitamin D is just a hormone, and not a vitamin?

Rickets still occurs in Africa with abundant sunlight, but with polio still present. (The strains that come from vaccines are usually not counted.)

by accidentallfact

6/24/2026 at 1:57:43 AM

Misinformation.

As somebody who spends an insane amount of time inside, the lack for exposure to the Sun mot just affected vitamin D levels but eyes sight too, they were terrible, and also mood.

Taking vitamin D pill instead of Sun is not the same.

by h4kunamata

6/24/2026 at 7:54:39 AM

tl;dr: The combination of vitamin D/MG cured heart arrythmia and mild depression I suffered from for almost 20 years, so I do not think it is worthless.

I had ventricular extrasystoles for a very long time of my life (18-37). This is a mostly harmless arrytmia that feels like one beat out of the normal rhythm. Around 18, I noticed it for the first time. It came and went, usually I had this for ~3 weeks and then it was gone. Over the years however, I got more and more of those and at the age of 30, I had them ~70% of the year at a rate of 5-6/min. In parallel, I felt stressed and depressed. Not from the fact that I had those, I got used to that over the years, which was not easy.

The doctors I went to said: Harmless, learn to live with it, you will still get very old. Especially the five cardiologists but also the "normal" doctor I saw never took that serious at all. I kept a diary over the years and knew that those could fully go away and I had the feeling that it was somehow correlated with what I eat. Whenever I said that, the response was: "Unlikely, you just don't pay enough attention and do not notice them anymore". Treatment advice was: Live with it or get a catheter ablation done.

Then I then went to a different doctor who actually listened to me when I said they could fully go away. She tested me for vitamin D, B12, magnesium, potassium, iron and a few other things. It turned out that I had a strong vitamin D deficiency (12 ng/ml) and a mild MG/K/B12 deficiency.

Then I took some supplements (a bit of D/MG/K/B each). That helped a bit, but not always and not consistently, but I could definitely tell that there was a relation to taking something or not. I prefer a healthy diet over supplements, so I was not very consistent taking those and when everything was good I simply stopped. The fact that this did help, but not always, kept bugging me though and I wanted to figure out what exactly helped. Long story (~5 years of experimenting) short: It most likely was the combination of D and MG, taking one in isolation did not always improve things. There seems to be a mutual dependency between them, which also seems to be studied to some extend (I started to read med publications at some point, e.g. [0]), but I am a computer scientist and not a doctor so take this with a grain of salt and definitely do not just take stuff without measuring the actual levels first.

Today, I occassionally take supplements (still do not like the idea of taking them on a regular basis) and get my D level tested every once in a while. It is now usually ~30 ng/ml which is still a bit low, but the extrasystoles are fully gone (I am 44 now).

[0] Role of Magnesium in Vitamin D Activation and Function, https://pubmed.ncbi.nlm.nih.gov/29480918/

by waffle-fry-pan

6/24/2026 at 10:32:26 AM

Yes magnesium seems to be quit a common deficiency because the heavy use of fertilizer depletes the density of minerals in the food chain. Also magnesium is a very important co-factor in the use of Vit D, so supplementing with a magnesium deficiency might not be of much use. Sadly this seems overlooked in most studies

by charlysisto

6/23/2026 at 7:46:42 PM

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.

by OutOfHere

6/23/2026 at 8:30:25 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.

by gblargg

6/23/2026 at 9:10:11 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.

by OutOfHere

6/23/2026 at 10:23:33 PM

If most people have a significant Vitamin D deficiency, then I agree that my comparison was absurd.

by gblargg

6/23/2026 at 10:32:03 PM

by d2kx

6/23/2026 at 10:45:52 PM

Without supplementation, yes, most people do have a substantial deficiency. There also exists the sufficiency range which is higher, and the optimality range which is slightly higher still.

by OutOfHere

6/23/2026 at 9:01:23 PM

[dead]

by tonetheman

6/24/2026 at 11:32:12 AM

[flagged]

by m00k3r

6/23/2026 at 9:19:21 PM

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

by burnte

6/24/2026 at 11:34:28 AM

Fake science at its best.

by crunchiepooker

6/24/2026 at 4:53:03 AM

The veracity of this article depends on who paid you for it, if at all.

by livingbuddha26