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Earlier quoted context omitted.
I think just as likely is the general problem of people who take supplements being generally more conscientious and less likely to engage in risky behaviours (e.g. wearing sunscreen in summer)
Or they are supplementing because they don't get much sun to begin with
People who avoid the sun more likely to take vitamin D supplements?
I don’t have access to the full paper, but I would expect that they at least tried to control for sun exposure. In general, if you can think of an obvious confounding factor in about five seconds, then it’s a safe assumption that professional researchers thought of it too.
I work in academic medicine. I read a lot of papers. This is not at all a given in my experience, except maybe in the tippy top journals (Nature, NEJM). When in doubt, read the paper, see if they mention the confounder you thought of.
I see research on essential vitamins all the time on HN. It really makes you think. There's cohorts who will debunk the studies based on methodology or glaring flaws. There's cohorts who will provide anecdotal evidence in support. There's even cohorts who will bring up a history lesson/"conspiracy" we all forgot about. It really makes you wonder about essential vitamins though. There's so many of these types of studi…
> experts continue to weigh in that we don't get enough essential vitamins and minerals through our diets
First, would be better to list some specifics rather than "experts say". But even if so, saying that people don't get enough of some micronutrient X from food, it doesn't necessarily follow that supplementation with pills will lead to better health (except in some specific and extreme circumstances that rarely affect people these days, e.g. scurvy).
Second, this was not the entire controversy around Pauling's vitamin C fantasy. His recommended doses were orders of magnitude larger than recommended amounts - it wasn't just about being "more personalized". Nevermind that Pauling's vitamin C theories have been thoroughly disproven.
I was told recently that US Doctors have lost their license over this topic; no idea if that is true.
Earlier quoted context omitted.
Doctors recommend supplementing vitamin D if you have a measured deficiency. Most people naturally settle to 20 ng/mL or higher, and just incidental exposure, or eating certain foods can help you either absorb or synthesize it. There are also people, like me, who no matter what, we can't make as much vitamin D for whatever cluster of genetic factors causes that. Some of us are always tired unless we take 50,000 IU of…
That’s over double the dose considered “safe”. Obviously, I’m not suggesting you do otherwise; it’s just way outside the bounds of what most adults would do unless directed to by their physician.
https://www.ncbi.nlm.nih.gov/pubmed/19667143
Must be much higher in sunnier regions.
Earlier quoted context omitted.
Did the study not control for confounding factors?
It did, they state that right in the summary.
It's easy for me to imagine tons of confounding factors that are associated with vitamin supplementation, e.g. wealth (wealth is associated with better health outcomes nearly everywhere you look), diet in general, exercise levels, etc. I highly doubt they accounted for all of these.
Earlier quoted context omitted.
This is the most plausible reason.
The most plausible reason is that the scientific peer-reviewed result is correct, not the tiring "correlation does not imply causatian" commenter on HN who at most skimmed the paper. 2009: > Epidemiological data show an inverse relationship between vitamin D levels and breast cancer incidence. In addition, there is a well-documented association between vitamin D intake and the risk of breast cancer. Low vitamin D int…
Quite the odd take given the last sentence in the abstract of this paper is essentially "correlation is not causation":
> In conclusion, regular use of vitamin D associates with fewer melanoma cases, when compared to non-use, but the causality between them is obscure.
Use of vitamin D supplement is also probably correlated with sunscreen use. That is, health-conscious people use both.
Most men never use sunscreen, including those who spend a great deal of time outdoors. I seriously doubt that cohort takes vitamin D.