Vitamin D, part 3 – The Evidence • Hacker News Board

Re: Vitamin D, part 3 – The Evidence

#151

Post by ljhsiung » Tue, Sep 08, 2020, 6:16 PM UTC

dcx wrote: post #92

This seems like it might be a little selective. What about these [1] [2] randomised controlled trials that show vitamin D supplementation has an effect on IBS symptoms? Or this [3] double-blinded trial showing supplementation improved sleep quality in people with sleep disorders? Or this [4] one showing improvements in depressive symptoms in overweight and obese subjects? The study cited in TFA is large but only uses…

Did you read the article?

> It is an essential hormone, definitely, but not a magical pill that will ward off disease. There are conditions that benefit from Vitamin D supplementation - for hypoparathyroidism, a condition that can cause dangerously low calcium levels, Vitamin D is lifesaving. For otherwise healthy adults, the benefit is less clear.

Takeaways: it's not clear what preventative benefits it has.

Even to use your vitamin C example, it's also widely touted to take vitamin C for general well being, such as helping colds. But its preventative benefits aren't clear [1]. Nobody has ever said vitamin C is useless, but it's just not a panacea (much like the article claims about vitamin D).

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1160577/

Re: Vitamin D, part 3 – The Evidence

#152

Post by davinic » Tue, Sep 08, 2020, 6:17 PM UTC

goda90 wrote: post #81

Nursie wrote: post #53

Earlier quoted context omitted.

But we can see how supplementation affects outcomes, and it turns out that so far the results on that are pretty 'meh', unless you're supplementing specifically for severe vit D deficiency.

I guess my point is, if outcomes are affected by a couple dozen variables, unless we can control for all those variables, then we might not see any affect from this one variable. And there is a limit to how many variables we can reasonably control for.

And also the effects of those couple dozen are nonlinear and the degree of nonlinearity probably varies from subject to subject.

Re: Vitamin D, part 3 – The Evidence

#153

Post by tchaffee » Tue, Sep 08, 2020, 6:19 PM UTC

0-_-0 wrote: post #131

tchaffee wrote: post #127

Earlier quoted context omitted.

> It must be important if it was worth evolving white skin over Where is the evidence that we evolved white skin to produce more vitamin D? Light skin in Europe may have evolved as a widespread thing as recently as 8,000 years ago [1], which doesn't support the idea that it was essential for survival in northern less sunny areas. Are there any studies giving strong evidence as to the causation for evolving white skin…

From the article you linked: "A sun lower in the sky and shorter day lengths would have favored skin that more easily synthesized vitamin D." The article also points out a correlation between latitude and light skin, so the evidence is pretty strong (based only what you linked) for why light skin evolved.

If you look at the full quote, the purpose is not to confirm your theory but to inject healthy doubt in your theory:

"A sun lower in the sky and shorter day lengths would have favored skin that more easily synthesized vitamin D. But researchers are now learning that other factors must have been at play."

> The article also points out a correlation between latitude and light skin

Well yes, exactly. Correlation. I asked for causation, which it seems you are still lacking.

Re: Vitamin D, part 3 – The Evidence

#154

Post by glofish » Tue, Sep 08, 2020, 6:23 PM UTC

tarsinge wrote: post #129

devaboone wrote: post #19

Earlier quoted context omitted.

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.)

I’m healthy, fit and relatively active (3-4 hours exercise / week, 30-1h walk everyday), and I just tested relatively low in Vitamin D (before winter even started). What should I do?

As the paper states the only effect of Vitamin D supplementation is that it reduces Vitamin D deficiency.

Re: Vitamin D, part 3 – The Evidence

#155

Post by tarsinge » Tue, Sep 08, 2020, 6:23 PM UTC

citruscomputing wrote: post #136

tarsinge wrote: post #129

Earlier quoted context omitted.

I’m healthy, fit and relatively active (3-4 hours exercise / week, 30-1h walk everyday), and I just tested relatively low in Vitamin D (before winter even started). What should I do?

Talk to your doctor.

I’m not sure my doctor has access to better studies than what is in the TFA. My question is weirdly formulated, what I ask is is supplementation useless given what we know? Or is it safer to stay in the (arbitrary?) recommended range? What I get from the parent post is that given low vitamin D is a symptom of poor health, supplementation is useless if someone is in good health.

Re: Vitamin D, part 3 – The Evidence

#156

Post by glofish » Tue, Sep 08, 2020, 6:25 PM UTC

copperx wrote: post #22

glofish wrote: post #16

Earlier quoted context omitted.

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?

for starters one is in the gut the other in the skin, sounds like a fundamental difference to me

Re: Vitamin D, part 3 – The Evidence

#157

Post by dnh44 » Tue, Sep 08, 2020, 6:29 PM UTC

scott_s wrote: post #43

black_puppydog wrote: post #29

Earlier quoted context omitted.

> 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…

> This is a departure from the discussion of supplementing vitamin D though, isn't it? I don't think so, no. If my hypothesis is correct, the problem is not that they didn't go outside and play sports. The problem is that they are sick , and sick people don't go outside as much. Forget Vitamin D for a moment. Imagine that every time you were outside for an hour, the Outside Fairy granted you one Outside Token. Over t…

That’s very true, but Outside Tokens are really cheap and are low risk so encouraging people to buy them seems like a reasonable hedge to make until the hypothesis can be proven.

Re: Vitamin D, part 3 – The Evidence

#158

Post by gambler » Tue, Sep 08, 2020, 6:36 PM UTC

This picture in the article is misleading:

https://static.wixstatic.com/media/3e0600_a25ba8bbf26b47a096...

At the very leat, vitamin D does seem to prevent respiratory infections. The article even admits as much later on. There are several RCTs that verify this. So why put a red cross next to "prevention of respiratory infections"?

Also, worth reading:

"Why randomized controlled trials of calcium and vitamin D sometimes fail"

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427206/

Re: Vitamin D, part 3 – The Evidence

#159

Post by chmod600 » Tue, Sep 08, 2020, 6:37 PM UTC

scott_s wrote: post #124

chmod600 wrote: post #73

Earlier quoted context omitted.

It has a green check next to "treatment for Vitamin D deficiency". What part of the article says that you should just ignore low vitamin D levels?

"Deficient" is not the same as "lower end of the normal range." If you suspect you are deficient, go to a doctor.

I said "low" not "lower end of normal". What part of my suggestion is refuted by the article?

Re: Vitamin D, part 3 – The Evidence

#160

Post by 0-_-0 » Tue, Sep 08, 2020, 6:39 PM UTC

tchaffee wrote: post #153

0-_-0 wrote: post #131

Earlier quoted context omitted.

From the article you linked: "A sun lower in the sky and shorter day lengths would have favored skin that more easily synthesized vitamin D." The article also points out a correlation between latitude and light skin, so the evidence is pretty strong (based only what you linked) for why light skin evolved.

If you look at the full quote, the purpose is not to confirm your theory but to inject healthy doubt in your theory: "A sun lower in the sky and shorter day lengths would have favored skin that more easily synthesized vitamin D. But researchers are now learning that other factors must have been at play." > The article also points out a correlation between latitude and light skin Well yes, exactly. Correlation. I aske…

I read the article but failed to see what doubt it sheds on the idea that light skin evolved to increase vitamin D production. Could you help me find it please?

You asked for evidence of causation, which I provided. Correlation of latitude with skin colour is evidence of causation. Light skin colour providing vitamin D while increasing skin cancer risk is evidence of causation. No other known advantage of light skin colour existing is an evidence of causation. Taken together, there is strong evidence of a causative link between the evolution of white skin and vitamin D production.