Vitamin D is an important protection

Vitamin D is an important protection against respiratory diseases and coronavirus.  Vitamin D comes mostly from sun exposure and the black and brown skins absorb it more slowly and less than whiter skins.  Maybe that is an additional reason why black and brown skinned people are dying more from the virus.  (As well as all the reasons in the news now).

There is a serious study on Vitamin D in the British Medical Journal BMJ 15th Feb 2017. Randomised, dble blind, placebo controlled, n=10,933.

The protective effect of Vit D ranges from 12% to 70% less respiratory infections, the higher rate in those who were deficient in Vit D.

25 micrograms = 1000 IU. Recommended doses vary a lot, you can read up on that, D is not expensive.