Comment by kccqzy

PSA that deficiency in Vitamin D also leads to cognitive decline including dementia. https://pmc.ncbi.nlm.nih.gov/articles/PMC6132681/

I find the risk-award very clear: if you are not deficient, taking normal* amount of Vitamin D supplement has no adverse effects; but if you are deficient, the risk is quite high.

*: The normal amount is 600 IU. The recommended upper limit is 4000 IU. The gap is wide.