Verdandi wrote:
Frakkin wrote:
All I know is too much vitamin D taken as a supplement can shorten your lifespan.
Could you elaborate on this? I can find nothing relevant via google.
I think it's possibile she is be referring to taking multivitamins. There have been some weak correlations found in observational studies between taking multivitamins and a slight increase in all-cause mortality. But there is nothing I have seen linking D3 supplements specifically with shortened lifespan. But if you want the boring details about why this makes little sense, here they are.
The D3 we get in supplements is bioidentical to that we produce on our skin (in fact, the D3 in supplements is generally harvested from sheepskin). D3 is created on the skin when UV-B rays interact with a form of cholesterol. It then binds with oil on the skin and is absorbed and carried by the blood to the liver, where it is converted to calcidiol , which is then the form of vitamin D that is used by all the cells in the body. On the other hand, when we ingest D3 as a supplement, it binds with fat in the stomach, is absorbed in the intestines, and then is carried by the blood to the liver where it too is converted to calcidiol. So while the two forms enter the body in different ways, once they get into the bloodstream, their paths and functions are identical.
Since we absorb 10,000-20,000 IU of D3 from just 10 minutes of summer sunlight, and since we evolved in equatorial Africa, where the sun is at "summer" strength all year, there is absolutely no reason to think that taking 1/10th that much via supplements should be in any way dangerous, and, in fact, it could well be inadequate.
An additional problem with observational studies (like the few that have been said to show dangers with multivitamins) is that they are intended to unearth correlations for further study in double-blind trials. And while the studys' authors almost always know this, they also know that if they present some sensationalized sentences in their conclusions and then include those sentences in a press release, than can get huge media attention. This might get them lots of grant money, but it also is a terrible way to mislead and confuse the general public.