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Comment by cpncrunch | Hacker News Reader

Not a very good review. We know that sunlight exposure is associated with lower all-cause mortality [1]. However, vitamin D supplementation has no effect on mortality [2].

Current thinking is that it is the nitric oxide rather than vitamin D that causes the benefit from sunlight [3].

So, if you want to have the best of both worlds, you should go out in the sun rather than using vitamin D supplements.

[1] https://www.ncbi.nlm.nih.gov/pubmed/24697969

[2] https://www.ncbi.nlm.nih.gov/pubmed/31405892

[3] https://www.karger.com/article/FullText/441266

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Not enough existing research controls for when in the day vitamin D is taken or for other related nutrient levels (K, Mg).

Vitamin D is part of a whole complex network of signaling processes related to (at the very least) regulating circadian rhythms and how is calcium absorbed and used in the body.

I could see how taking vitamin D in the evening would actually be harmful if it disrupts melatonin synthesis. Do existing studies control for this? If they are, they're hard to find.

Until I see vitamin D studies controlling for those things, I take meta-analyses like that with a grain of salt. And I'll keep taking vitamin D in the mornings + magnesium in the evenings when I'm depressed in the winter. It sure seems to help.

Said as respectfully as I can, it seems like there's a lot of post-hoc justification from the supplement crowd.

I.e. 'Well, no effect was observed because Y wasn't done simultaneously.'

Which isn't to say vitamins aren't under-studied and -prioritized.

But is to say, it feels unscientific to always quibble over experiment design after the results show no effect.

> it feels unscientific to always quibble over experiment design after the results show no effect.

Respectfully, this is exactly what science is. The process of finding potential confounding variables and controlling for them in a new study is critical.

The OP isn’t saying the original study is wrong, or falsified, or whatever, just that it might not account for a particular effect. Someone should study that effect!

There is a lot of untestable post-hoc armchair experiment criticism from the supplement crowd, but this isn’t an example of that!

There are an infinite number of confounding variables in biological systems. Ergo, there are an infinite number of reasons to dismiss any particular study.

OP's suggestions are tightly scoped and proceed from a basis, but there is a point where you're dismissing concrete evidence on the basis of supposition.

I'm not usually motivated by these discussions, but it does seem like it's worth testing the difference between morning and evening for taking something that's related to circadian rhythms.

>I could see how taking vitamin D in the evening would actually be harmful if it disrupts melatonin synthesis.

How would this work? From my understanding, vitamin D blood concentration takes quite a while to build up due to the fat soluble nature, and taking a single pill doesn't cause an immediate spike just like staying inside for an entire day doesn't cause a drop.

Here's a study showing a marked circadian rhythm in serum 25-hydroxyl vitamin D levels. There are actually lots of theoretical papers about this kind of thing, yet somehow so many of these nutritional studies seem oblivious to them or something.

https://pubmed.ncbi.nlm.nih.gov/25788054/

If you dig a little you'll find a similar situation with Mg/Ca/vitamin K/vitamin D. There are lots non-controversial evidence and understanding of the relationships between them, but the nutritional studies on vitamin D supplementation seem all but oblivious to that information.

So that study seems to conclude that the blood concentration of vitamin D varies according to circadian rhythms.

That's an interesting finding, but what I'm saying is that I don't think taking a vitamin D pill has an immediate effect on your body's vitamin D levels. That's why it takes weeks or months of supplementation before you see it reflected in blood tests.

One issue here I'm realizing is in a difference of assumptions... I'm used to taking vitamin D3 drops under my tongue, which I imagine absorb differently than capsules.

But even so, fat soluble substances can get into the blood pretty quickly when you ingest them, well within the timespan of one day.

So I'm not sure if I understand your reasoning. Can you link to a source?

Something I'm reading now that sounds similar to what you're saying is that during supplementation, it takes a while for serum vitamin D levels to reach a steady state. Maybe that's what you're referring to?

Edit: check this out https://www.sciencedirect.com/topics/medicine-and-dentistry/...

> After an oral dose of vitamin D, blood levels begin to rise at 4 hours, peak by 12 hours, and return to close to baseline by 72 hours.

In this article, I take "baseline" to refer to what I called "steady state" earlier in this comment.

I've been wondering about melatonin.

It started when I heard about umbilical stem cell injections on the joe rogan episode with mel gibson. I started to look into it, and mesenchymal stem cells seem to really "fix things" that have broken down in your body. The more I read about them, the more I think they're going to be a powerful way of staying younger and fighting aging.

And then I read that melatonin is what regulates the natural generation of them in our body. Hmm.. probably something you shouldn't disrupt.

I don't know about all-cause mortality, but this recent review says vitamin D supplementation definitely helps with respiratory infections, which is more germane at the moment.

https://www.ncbi.nlm.nih.gov/pubmed/28202713?dopt=Abstract

Yeah, I was going to post something similar. Lots of evidence for vitamin D deficiency causing all sorts of issues. Very thin evidence that supplementation helps. Better evidence that producing vitamin D naturally via sunlight helps. Which suggests that the D may well be a mostly irrelevant byproduct of the pathway that matters.

Author of originally linked post here. I welcome your constructive suggestions to make the review better. I intend it to be the best review on the internet of the best-available data on vitamin D & COVID-19 and think that it probably is currently.

The best method of increasing D levels to avoid deficiency is not the main point of the article. I have added a paragraph to note the debate on whether sun is better than supplements, but covering that debate adequately is beyond the intended scope. The urgent point is to get more data on D levels by patient vs. case severity/outcome. Such records should already exist in sufficient quantity if we can just get the right people from the right orgs (Kaiser? VA? big hospitals?) to simply aggregate the records and analyze or partner with researchers who will.

Every time I consider adding vitamin supplements to my diet, I'm confronted by the fact that the entire supplement industry is unregulated in the United States. How do you know the supplement you're taking is pure and of the listed dosage? You don't.

I'm pretty sure the "regulators" don't examine every molecule of atmosphere going in your lungs, nor every wild blueberry that gets eaten. If I walk out my house to the nearest farm and buy some chickens, I somehow don't need a "regulator" to bless the occasion. And yet, well-"regulated" iatrogenic deaths cause non-negligable mortality in USA [1]. You can compare the rates of poisoning yourself (dietary supplements vs regulated prescription drugs) as reported by the American Association of Poison Control Centers [2]. The rates of death due to contamination, or for other reasons, are not comparable.

This is meant to suggest you may wish to revise your risk analysis.

[1] https://jamanetwork.com/journals/jamanetworkopen/fullarticle...

[2] https://www.aapcc.org/annual-reports/ , in particular see page 1239 of the 2018 full report https://piper.filecamp.com/uniq/meDKF2EpE2jsmTOs.pdf

If I buy chicken meat and the package has pork in it, I'm going to notice. But if a vitamin supplement is actually nothing but chalk, would I notice? Probably not. Nor would it poison me, but I think getting ripped off is more likely than being poisoned.

There are a couple of well-regarded private organizations in the U.S. which write standards for and verify supplement manufacturers, one of which is United States Pharmacopeia (USP). See https://en.wikipedia.org/wiki/United_States_Pharmacopeia They serve a similar function as UL does for electrical and fire safety; and like UL some their standards are incorporated into the regulations of the U.S. and other countries.

Only a handful of well-known supplement makers are USP verified, AFAICT. (Note, verified is different than simply claiming to adhere to USP standards. It's like the difference between FIPS compliant and FIPS certified.) I try to buy Nature Made, a common brand in pharmacies which will usually carry the USP Verified mark, though it's product specific (see http://www.naturemade.com/usp).

Like with UL, this doesn't mean you're not buying useless crap, but it means you're unlikely to buy crap that will kill you, which is adulterated, or which isn't manufactured to minimum standards of safety (e.g. lead content--many supplements contain surprising levels of lead[1]).

[1] Not surprising if you consider how ubiquitous lead is in industrial environments, and that using non-contaminated materials in your food processing chain requires comprehensive, sustained efforts which translate to $$, especially in an age when so much industrial equipment comes from overseas.

EDIT: Consumer Reports details four private verification programs for supplement makers, including a table of testing regimes: https://www.consumerreports.org/supplements/how-to-choose-su... To me USP looks the best--store bought samples, more regular testing, stricter criteria for ingredients. The other 3 players they discuss are NSF International, UL (branching out, I guess), and ConsumerLab.com.

Moreover, more outside time is associated with many other healthful activities. The correct model is that people who care about their health spend more time outside and therefore have higher vitamin D levels, not that higher vitamin D levels cause a dramatic effect on health. Taking vitamin D supplements if you are not deficient isn't going to make you care about your health more and is unlikely to have a significant effect on your mortality.

Don't people who take Vitamin D supplements _also_ care more about their health though?

Eh or just want to pretend to care about their health and the cost of being guilt free about it is a monthly vitamin D bottle.

In that case, the direction of causality is also reversed. Caring about health -> higher vitamin D, not the other way around, exemplifying my point. It's the caring about health that significantly reduces mortality, not the vitamin D, so implementing vitamin D supplementation as public policy to fight Covid-19 is unlikely to have an effect.

Fwiw, much of Western Europe is vitamin d deficient through no fault of their own. There's just too much cloud cover. Thankfully the past few weeks have been really nice.

Is it the UV, or just the visible lights? i.e., can you get some of the benefit from LEDs at sunlight temperature?

UV-B makes your body produce Vitamin-D.

So, special LED that can emit UV helps for that, too, but carefully.

Oh and ordinary window glass completely blocks UV rays.

Glass actually fully blocks the helpful UV-B rays while still allowing some amount of harmful UV-A rays through.

There is an interesting illustrating picture about this. From a trucker where the sun always only hit one side through glass:

https://www.cbsnews.com/news/trucker-accumulates-skin-damage...

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