Live data from Hacker News

Vitamin D, part 3 – The Evidence

devaboone.com

21–30 of 218 posts

Re: Vitamin D, part 3 – The Evidence

#21
post #10

If deficiency is linked to all these maladies then why aren’t we seeing them occur with less frequency in areas that get full sun year round?

Do areas that get full sun year round have people with more vitamin D? Those places have people with darker skin which blocks vitamin D production. Actually, the only reason white people exist in the first place is because of vitamin D, so you would expect vitamin D to have strong positive effects based on this fact alone.

Re: Vitamin D, part 3 – The Evidence

#22
post #16
post #2

So Vitamin D deficiency is linked to cancer, heart disease, respiratory infection, stroke, diabetes, and death. But taking it as a supplement helps with none of the above. What is a reasonable hypothesis then? That having an active lifestyle that brings you outside in the sun both causes your Vitamin D to go up, and is correlated with better physical health in general?

There is a fundamental difference between vitamin D generated in your skin versus vitamin D placed in your gut. The mechanisms by which it acts and the effects it has on you are probably radically different. We are more than just a pile of various materials.

What is that fundamental difference?

Re: Vitamin D, part 3 – The Evidence

#23
post #5
post #2

So Vitamin D deficiency is linked to cancer, heart disease, respiratory infection, stroke, diabetes, and death. But taking it as a supplement helps with none of the above. What is a reasonable hypothesis then? That having an active lifestyle that brings you outside in the sun both causes your Vitamin D to go up, and is correlated with better physical health in general?

It might just be that the production of vitamin D via sunlight has other effects on the body, perhaps vitamin D has been a proxy for those effects but for obvious reasons taking it as a supplement doesn't trigger the same outcome. It's unfortunate that exposure to UV is so harmful, I'm left wondering if trials using UV lightboxes to stimulate vitamin D production would change the kinds of outcomes (cancer, heart dise…

Exposure to UV light is not "so harmful".

What is harmful is being indoors all the time, and getting out so rarely that you get sunburned in short amount of time. Far more damage is done by being indoors too much than being outdoors too much.

The white skin has evolved because the body needs sun and UV light to function, one would die otherwise.

Re: Vitamin D, part 3 – The Evidence

#24
post #10

If deficiency is linked to all these maladies then why aren’t we seeing them occur with less frequency in areas that get full sun year round?

Linked does not mean caused by. In fact, this entire post is laying out the evidence that low Vitamin D is unlikely to cause any of these illnesses.

Re: Vitamin D, part 3 – The Evidence

#25
The most obvious evidence to me has always been that Europeans are not black. A change like the loss of melanin requires selective pressure, which in this case was likely furnished by less vitamin D as we migrated away from the equator. The pressure must have been significant since being white carries a big downside: higher vulnerability to sunburn and skin cancer. When I lived in Cali I always envied my darker skinned friends who did not have to smear goo on themselves at the beach.

I gotta say though... the world would have far less race problems had that odd little quirk of photosynthesis of a key nutrient not existed.

Re: Vitamin D, part 3 – The Evidence

#26
post #2

So Vitamin D deficiency is linked to cancer, heart disease, respiratory infection, stroke, diabetes, and death. But taking it as a supplement helps with none of the above. What is a reasonable hypothesis then? That having an active lifestyle that brings you outside in the sun both causes your Vitamin D to go up, and is correlated with better physical health in general?

That is a reasonable hypothesis. Also, people who are very ill are less likely to get outside and get enough sun, so they will develop low Vitamin D. Vitamin D is likely a marker of poor health. (Once the Vitamin D gets low enough, we do see direct harmful effects from it (think rickets in children), and this may contribute to poor health at that point.)

Have there been any studies that test if the absorption of Vitamin D (from supplements) is influenced by disease compared to healthy people?

Re: Vitamin D, part 3 – The Evidence

#27
post #15
post #2

So Vitamin D deficiency is linked to cancer, heart disease, respiratory infection, stroke, diabetes, and death. But taking it as a supplement helps with none of the above. What is a reasonable hypothesis then? That having an active lifestyle that brings you outside in the sun both causes your Vitamin D to go up, and is correlated with better physical health in general?

I would frame it in the opposite direction: having a serious illness is correlated with low levels of Vitamin D. People with a serious illness may stay inside more, and go outside less. It's possible that "low levels" of Vitamin D are still within the healthy range, and they merely are an indication of how much time the person has spent outside during the day. In other words, it's possible that Vitamin D is pure symp…

[deleted]

Re: Vitamin D, part 3 – The Evidence

#28

TL;DR: skip to the part "The areas in which meta-analyses have identified benefits from Vitamin D" Also "Vitamin D failed to prevent cancer, stroke, heart attack, or cardiovascular death. " Which is fair enough. But at least for the cardiovascular diseases mentioned, I don't think it was expected. And of course, this does not mean anything against the role of Vitamin D in Covid prevention Basically: don't dismiss X f…

I find it odd to encourage people to skip what I consider the most important conclusion for most people: "Vitamin D does not appear to prevent disease in healthy adults."

Re: Vitamin D, part 3 – The Evidence

#29
post #15
post #2

So Vitamin D deficiency is linked to cancer, heart disease, respiratory infection, stroke, diabetes, and death. But taking it as a supplement helps with none of the above. What is a reasonable hypothesis then? That having an active lifestyle that brings you outside in the sun both causes your Vitamin D to go up, and is correlated with better physical health in general?

I would frame it in the opposite direction: having a serious illness is correlated with low levels of Vitamin D. People with a serious illness may stay inside more, and go outside less. It's possible that "low levels" of Vitamin D are still within the healthy range, and they merely are an indication of how much time the person has spent outside during the day. In other words, it's possible that Vitamin D is pure symp…

> It's not even necessarily the case that going outside is healthy, but that healthy people tend to go outside more.

This is a departure from the discussion of supplementing vitamin D though, isn't it?

I guess the treatment "go out and do sports" is a very different one compared to "X amount of vitamin D per day as a supplement" and the former may indeed be healthy, while the latter may not be, even though they both result in higher levels of vitamin D.

Re: Vitamin D, part 3 – The Evidence

#30
post #11
post #2

So Vitamin D deficiency is linked to cancer, heart disease, respiratory infection, stroke, diabetes, and death. But taking it as a supplement helps with none of the above. What is a reasonable hypothesis then? That having an active lifestyle that brings you outside in the sun both causes your Vitamin D to go up, and is correlated with better physical health in general?

There are thousands of reasonable hypothesis, and it is extremely costly (and in some cases, nearly impossible) to test. e.g. our bodies need sunlight and cholesterol in order to synthesize vitamin D; This process also apparently has some other outputs like NO which are much harder to measure since they get used quickly. It is possible that vitamin D is merely (mostly) a measure of the prevalence of this process, and…

The NO production might explain most of this through it's anti-inflammatory properties. The instant reduction in blood pressure is likely just the tip of the iceberg for UV's effects on the body.
Post reply on HN