Comment by soneca | Hacker News Reader

Comment by soneca | Hacker News Reader

I wonder if Vitamin D would be an odd biological case of the adage ”if a metric starts being used as a goal, it ceases to be a good metric”.

From my understanding, Vitamin D has strong evidence of being a good marker of good health. A certain level of Vitamin D is strongly correlated with a lot of health indicators. But there is no strong evidence so far that it’s a cause of good health.

If that’s the case, that Vitamin D doesn’t cause good health, it just happens to be present in people with good health — and I could be wrong in both of my previous statements, I am not a specialist, I just read specialists claiming this. So, if that’s the case and Vitamin D supplement intake becomes widespread (a lot of dairy products in the US includes Vitamin D already), it might interfere in research trying to understand the relation of Vitamin D and good health.

Not just research, but a doctor checking a patient blood exam wouldn’t notice anymore the low Vitamin D and wouldn’t recommend a, probably beneficial, larger exposure to the sun.

Vitamin D is a hormone and it seems pretty clear that it plays a significant role in a number of body processes that contribute to overall health, so it doesn't seem likely that it is just a marker; it actually does help you directly, so it still makes sense to use supplements to raise your Vitamin D level if it's low.

What might well be true, IMO, is that if your Vitamin D level is low, and you can't get it back to normal with just sun exposure (which might well be an issue for people living at high latitudes, or as people age, since as I understand it your body's ability to synthesize Vitamin D from sun exposure decreases with age), you should not assume that supplements alone will be enough to protect your health. There might be other things you could do differently that would also help. In other words, low Vitamin D might be both a problem in itself (i.e., you need to get the level up) and an indirect indication of some other problem (which won't be solved just by getting the level up).

The problem is that, if the latter is the case, nobody seems to know very much about what other problems low Vitamin D might be an indication of, or what other interventions might be indicated if your Vitamin D is low, besides supplementation to get the level up. The only real advice that seems to be indicated, based on what we know now, is to take better care of your health in general--eat better, exercise more, get more sleep, etc.

You are absolutely right, for example there are many studies showing vitamin D may have a protective effect against multiple forms of cancer, here's a nice meta-study summing a bunch of them up:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1470481/

On the other hand another study has found that just taking a vitamin D supplement is not enough to statistically improve your odds of not getting cancer:

https://www.cancer.gov/news-events/cancer-currents-blog/2018...

Vitamin D is certainly important for a number of biological processes including the regulation of calcium in the body and that is well understood. But for things like cancer prevention and lowering the risk of heart disease it may simply be that naturally occurring vitamin D is just an indicator of other healthy habits like eating a diet high in fish and exercising outdoors etc.

> But there is no strong evidence so far that it’s a cause of good health.

The linked paper seems to contradict this pretty strongly.

E.g.:

> "vitamin D is a powerful nuclear receptor-activating hormone of critical importance, especially to the immune system."

That's just one example - the article mentions several others.

> I just read specialists claiming this

There are a lot of quacks in this field - are you sure you're not reading some of those?

> "vitamin D is a powerful nuclear receptor-activating hormone of critical importance, especially to the immune system."

This just means there is a plausible mechanism of action. It in no way implies positive health effects for particular levels (except possibly in limiting cases)

Wouldn't this make 'now' a good time to do a study on Vitamin D? Basically, give a grup vitamin D supplements, and compare to placebo group?

Because curing all the coronavirus histeria, i know people who've gone sunbathing for too long in relatively cold weather, because some study somwhere found out that a bunch of people who died from covid had very low vitamin D, and by correlation=causation logic, they though they needed more (but ignore the fact that most dead here were eldery in retirement homes, bedbound and pretty much never in the sun at all).

Yes, for example, vitamin D may not be an adequate substitute while artificial sunlight might be.

FDA approved vitamin D lamp:

https://www.sperti.com/product/sperti-vitamin-d-light-box/

Do read the instructions before using it, it has a 5 minute timer on it for a reason.

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