Vitamin D: More May Not Be Better
Benefits in healthy adults wear off at higher doses, research suggests
John Hopkins 2013
https://www.hopkinsmedicine.org/news/media/releases/vitamin_d_more_may_not_be_better

“...When they looked at deaths from all causes and cardiovascular disease specifically, those with blood levels of 21 nanograms per milliliter of 25-Hydroxyvitamin D — at the top of the range that the IOM considers “adequate” and at the low end of “normal” — cut their risk of death in half. Above 21 nanograms per milliliters, the data suggest that the protective effect appears to wear off...”