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I'm 10 years removed from life science research at this point... but aren't these vitamin studies a dime a dozen at this point? I don't think I see a comparison of outcomes between groups that were vitamin D deficient/insufficient vs vitamin D sufficient, which I think could be a bit more useful?
I'm actually getting submarine vibes from the amount of positive Vitamin D coverage I've seen recently
What does that mean?
That someone is pumping vitamin D supplementation promotion.

I have also my own example of N(1) where supplementing vit-D made me healthier and I am nerd sitting most of the time hidden from the sun.

Pre-Covid after start of supplementation I noticed less infections, easier hangovers overall better health.

That said I mostly sit inside by the screen and live in countries where is not that much sun so it is easy for me to get positive outcome of supplementation.

I think there is a lot of people like that and that is why there is so much positive reaction for D supplementation.

Yes most studies on micronutrient supplementation are badly flawed in that way. They typically give a supplement to the study group and a placebo to the control group, but since vitamins also come from other sources the supplements are only loosely correlated with actual levels.

A better approach is to pick at least two different target levels for separate study groups. Then use periodic blood tests to precisely titrate those levels using varying amounts of supplements as needed. If the results show a clear relationship between the different blood levels and the study goal then it's likely a real causal relationship exists.

Vitamin D is one of the most overstudied topics in medicine. Yes, there are probably aspects of vitamin D function that we do not understand well, but if there were a large signal for benefit, it should have been discovered by now.
and hasn't it been discovered by now? my understanding of all the studies I see is that they confirm and reconfirm the importance of vit d. I have a coworker whose doctor prescribes vit d shots every winter because he's so deficient. The big question is why preventative care such as this is not emphasized as much by the powers that be as therapeutics.
The US Preventative Services Task Force has recently reviewed the vitamin D literatue, it is summarized here:

https://www.uspreventiveservicestaskforce.org/uspstf/recomme...

Primary care is largely concerned with preventative care. It's not that we don't want to help, it's just that in many ways we are impotent. We generally do not change practice based on single studies. But since this post is about a single study, I'll share a recent RCT in The Lancet which showed no change in mortality and signals of increased cancer with vitamin D supplementation: https://www.thelancet.com/journals/landia/article/PIIS2213-8... .

That's why they add it to milk.
While the vitamin D result was significant, this is not a slam dunk result. 123 (treatment) vs 155 (placebo) had a confirmed autoimmune disease. Low incidence rate with a small effect size hamper the power here. This is somewhat expected given the complexity of autoimmune diseases; I would have been highly suspicious of a slam dunk, silver bullet result.
Talking about Vitamin D and calcifediol: why are we not informed that Calcifediol treatment (and as such Vitamin D supplementation) significantly reduces the chance of ICU admission and mortality in COVID-19 based on RCTs [1,2]?

[1] https://pubmed.ncbi.nlm.nih.gov/34097036/

[2] https://www.sciencedirect.com/science/article/pii/S096007602...

> why are we not informed

What do you mean? I've been bombarded with Vitamin D recommendations since COVID started, from my doctor through countless podcasts. It also comes up frequently in any online discussion about COVID. And before anyone suggests otherwise, yes, Dr. Fauci has also spoken about Vitamin D.

But Vitamin D isn't a magic bullet. It helps, but it's not a miracle cure like some of the internet articles or early ad-hoc studies would imply.

Podcasts, Twitter, Youtube, Fauci (informally): yes. Official medical recommendations: none that I am aware of.
Yeah, people have been talking about the decreased Vitamin D levels in COVID patients and suggesting supplementation since almost the very beginning of the pandemic. Maybe they just don't want to draw attention away from the fact that vaccination and masking are still by far the best means of avoiding hospitalization.
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iirc, the first mention I remember was from a Stanford, CA area Doctor who was not waiting for the CDC to make a press release before making a statement about what he saw anecdotally (~Nov 2019) given how quickly his hospital was overwhelmed. Specifically, he noted that patients with Vitamin D deficiencies were having the worst symptoms.
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Because at least for Vitamin D in general, there are a bunch of studies, and overall it looks like it probably doesn't work[0].

I'd recommend taking it anyway, but there are more than two studies and the results are not solidly on the side of "it works".

[0] https://astralcodexten.substack.com/p/covidvitamin-d-much-mo...

That article is badly outdated and incomplete. I recommend reading through this more comprehensive list of studies.

https://vitamin-d-covid.shotwell.ca/

Maintaining adequate vitamin D levels probably does "work" in the sense of reducing the risk of severe symptoms. It is not a magic cure and shouldn't be relied upon as an alternative to vaccines or other therapies.

I would like to take time to debunk that whole article, but let's just focus on the article [1] I shared and to debunk his argumentation for the preprint article [2].

To begin with, you have to understand that the vitamin D3 supplement we take is usually cholecalciferol, which is metabolised by our body over a period of weeks into calcifediol. The key takeaway is that the usual supplement takes weeks to be effective.

The RCT in article [1] is so strong because it supplements calcifediol at hospital intake, meaning the supplementation is immediately effective. So you can see that as a proxy for having supplemented with normal vitamin D for a couple of weeks prior.

In article [2], the one he is promoting, cholecalciferol (normal vitamin D) is supplemented. This means it is unlikely that it will have a significant effect during the first weeks of admission.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7456194/

[2] https://www.medrxiv.org/content/10.1101/2020.11.16.20232397v...

Most of these studies suck. For example, as mentioned in this response, https://academic.oup.com/jcem/article/106/12/e5271/6348963, to that first linked study (which may apply equally to the second, as it was just a trial for the subsequent study):

> However, the authors did not provide information on 25OHD serum levels after the supplementation, limiting the evidence of a causal link between vitamin D supplementation and the observed clinical outcomes.

IIRC, there was a similar study to the above that was retracted, in fact. Possibly even #2 above?

It’s an RCT. What will those measurements contribute? In addition, it is likely the measured serum levels will be lower because they are used up.
The first linked study was an observational cohort study, not an RCT. The second cited study was an earlier related pilot RCT by some of the same authors.

Here's a recent summary looking at both those papers and many others. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8787834/ TL;DR--it's all just too inconclusive at this point. Though as always everybody remains enthusiastic, notwithstanding that vitamin D papers have been perennial favorites long before COVID, without much to show for it.

FWIW, I think this is the retracted paper I had in mind earlier: https://retractionwatch.com/2021/02/19/widely-shared-vitamin... Somewhat similar design and at least one of the same authors. Retracted because it wasn't actually as randomized as claimed.

We need to understand the impact of increased vitamin D on vitamin D average vs vitamin D deficient people. I was vitamin D deficient, lowest part of the spectrum, and since taking daily supplements I noticed less health issues overall. I believe it also helps with my sleep cycle. YMMV I am regularly tested for vitamin D and its consistently above average, but you must monitor to not exceed the threshold.
Do you just swallow a pill?
Yep, it's the most insanely underappreciated public health intervention in history.
Many public health people say that iodized salt takes those laurels. Or maybe its the most bang for the buck, at an estimated $.05/person/year to prevent intellectual and developmental problems. Guess it depends on exactly what you mean.

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

Vitamin D is a fat soluble vitamin isn't it, so maybe we need more than just swallowing a pill. We have very bad data from most Vitamin D studies suggesting it does almost nothing. The people with high natural Vitamin D who spend 1-2h per day (exercising?) outside might just imply a proxy for a healthy lifestyle.

Alternatively Vitamin D might need to be a) taken in higher quantities than the studies have done b) taken with fat c) taken with other supplements K2, NAC, Magnesium (which people are also deficient in) etc.

We could probably come up with other theories why the trials and results don't add up. Nice to see an actually positive result from supplimentation.

>> who spend 1-2h per day (exercising?) outside might just imply a proxy for a healthy lifestyle.

Try living in the north. Being outside, exercising, and sunlight exposure are three unrelated activities for at least six months of the year. Vitamin D supplements are the only way short of tanning lamps.

Also make sure you're getting your calcium levels tested as too much Vitamin D can lead to hypercalcemia.
thanks for sharing, never knew this. Got a good source to read more up on it?
I had hypercalcemia and it was causing me headaches and short term memory loss. Two things i cut off that helped a lot 1. Vit d 2. Sony noise reduction headphones
For a daily dose as low as 2000 IU this is not going to be a concern for adults, especially when taken with a meal. Generally for avg+ weight males, even 5000 IU with a large meal is not going to cause issues with hypercalcemia.

Look to avoid added calcium in multivits first. Women and those concerned with bone health should supplement with boron instead. Dietary calcium should be more than enough in typical diets. The only calcium containing supp i might take would be calcium ascorbate (it's a fairly small dose of calcium).

Having wattage emitted in RF bursts 2mm from your head is never a good idea (yup, i wholly approve of avoiding this: "2. Sony noise reduction headphones").

i've been skiing 3-4 days/week with around 8 hrs out in the sun. Would this have the same beneficial effects on me? I am always deficient but i din't bother taking anything so far due to lazyness.
For Vitamin D synthesis, the sun needs to be at an angle of 50 degrees or higher. Depending on the latitude where you live, the sun may not get that high all winter so you may need to supplement.
Surely sunlight is still sunlight even if it's from a low angle?
From memory, it's not just about sunlight, but rather specific band of uv-light; and the atmosphere filters it when the sun is at specific angles. It's not as simple as "just sunlight".
No, the composition of sunlight literally changes throughout the day. When the sun is low in the sky in the morning or evening, light is traveling through more atmosphere than it is at noon. As light travels through the atmosphere, a certain fraction is scattered in a wavelength-dependent way. UV-B light--the Vitamin-D-causing kind--has a hard time passing through the atmosphere because of interactions with ozone molecules, so at grazing angles almost none gets through. However UV-A light is less affected by ozone and can still give you a sunburn. Interestingly, ordinary glass blocks both.
Or, I don't know...go outside if you need vitamin D.
Some of us live at higher latitudes and work during the day. It's not as simple or easy as just going outside.
No, this doesn't work. You'd have to be outside in summer sunlight with your shirt off to get enough.

In the Northern Hemisphere about half the year it's impossible to get enough Vitamin D by going outside.

If Russians can do it, so can you!

Don't be a small cat!

There are many photos of Russian children in a circle around a sunlamp with only bottom underwear on.
A quick search online suggests that Russians also tend to be at higher risk for vitamin D deficiency and that the local climate/weather is a large contributing factor. I feel pretty comfortable saying that people who live in northern climates like Russia should be getting their Vitamin D levels checked, and potentially taking supplements or using sun lamps.

Big cats especially need proper nutritional intake, or they'll turn into small malnourished ones :)

It's significantly below freezing in much of the northern U.S. and virtually all population centers of Canada.
Aha, didn't know you guys have it so rough up there.
Can't tell if trolling or if you genuinely believe north = up = closer to the day star
Indeed, I had no problems with vitamin D levels when living in Georgia (the state), especially since I regularly ran or otherwise exercised outdoors after work and most weekends year round (even when it got cold, it didn't get that cold, and there was no ice to speak of south of Atlanta). But during my first winter in Colorado, hah! Good luck getting sunlight during the week when the sun sets by 4:40pm and the sidewalks and trails you run on are covered with ice even if you do get outside before then.
There are many reasons why it's not that simple.

1. We need to dress up to go outside, exposing only minimal amounts of skin.

2. People of color produce less vitamin D (most likely due to skin pigmentation).

3. Pollution and shadows significantly reduce UV light within cities.

I recently read, via HN, that the sunlight that helps produce vitamin D is mostly taken in via the eyes.
Sun goes up at 09:34 and down at 15:16, most of us are at work. And that doesn't include the mountains blocking the sun, some weeks it barely goes above them. So there's light, but no direct sun light. And when it's -10C, only a few square centimeters of my skin is exposed to the elements, not really producing any vit D.
Also not much help if the daytime sky is clouded much of the winter. Might as well go outside in Alaska.
Above or below a certain latitude, sunlight cannot give you enough vitamin D during certain parts of the year.
And to add to that, skin pigment greatly influences all of this.
Rather decrease my risk of Melanoma from UV skin damage and just supplement Vitamin D by popping a few pills everyday
Well, gee, thanks. I'm in Central Europe and it's middle of winter.
Interesting, however statistical significance seems borderline at best
Don't exaggerate your daily dose. Its difficult to overdose, requires multiple exaggerated daily intakes for several months, but some individuals have managed to achieve dangerous levels.

"Vitamin D toxicity" https://en.wikipedia.org/wiki/Vitamin_D_toxicity

Yeah, but you have to be basically gobbling these pills to get anywhere near the dangerous levels. People dumb enough to do that are probably making all sorts of other poor decisions about their health and life.
i was once accidentally taking 25.000 IU daily for a few months instead of 5.000 (400-600 IU being official recommended dosages, although many sources claim that that's way to little, hence the 5.000). went to an endocrinologist for really weird bouts of whole body weakness and exhaustion after even light activity. nothing like i had ever experienced. lab results came back with a vitamin d level of the maximum measurement level (so probably more, maybe a lot more). that's when i realized i was taking 5 times more than i had planned. i looked up vitamin d toxicity and found fatigue and muscle weakness as symptoms and had the answer to my condition. i don't want to know what would have happened if i hadn't looked it up myself, because the doctor didn't even want to see me again, claiming by letter that my blood work was just fine. so yeah, pay attention to your supplement regime.
Really, best course of action is not to guess and just get blood work done regularly.

It builds up slowly enough that your doc may suggest mega-dosing for a few weeks to bring things back in line.

Pure anectdata on the auto-immmune thing: since getting my vitamin D levels up, my alopecia barbae has completely disappeared. It's pretty crazy cause it's something I've had my entire life (and very severe at times). My doc mentioned a link between auto-immune and vitamin D, and after bringing my levels back in line, all the patches filled back in. Pretty wild, tbh.

It's not just vitamin D toxicity, it's also Calcium toxicity.

For example, vitamin D3 (Cholecalciferol) increases Calcium absorption by 5-10x fold.

Besides, Calcium (surprisingly) are toxic for human bodies as well, in excessive amounts, and accumulates with age in body tissues.

Btw, vitamin D3 (Cholecalciferol) are commonly used as rat poison.

Wow, are there more medicine/rat poison, apart from warfarin?