Synthetic "Vitamin" D supplements are useless at best. -
One of the top boys of the mainstream press comes to the conclusion that the sun is actually not broken yet and popping in rat poison, aka synthetic "Vitamin" D supplements may not be a healthy idea either.
Btw., "Vitamin" D deficiency is caused by Magnesium deficiency but I guess it will take them some more years to come up with such a headline if any....

https://www.nytimes.com/2017/04/10/health/vitamin-d-deficiency-supplements.html?_r=1

There is no epidemic of vitamin D deficiency, experts say, yet pointless testing and treatment are rampant.