Vitamin D

Supplementing people who are genuinely deficient clearly helps, and vitamin D with calcium supports bone health. The large randomised trials that tested supplementation in people with adequate levels have repeatedly found no reduction in cancer, cardiovascular events or fractures. Your starting blood level, not the dose on the bottle, is what most of the evidence turns on.

Reviewed 2026-09-20

Official sources

Reviewed ingredient

This topic is also a reviewed ingredient, with dose context and claim-level evidence.

How this list was built

We searched Europe PMC for English-language papers published since 2016 whose title contains “vitamin D” or “cholecalciferol” or “25-hydroxyvitamin D”, kept meta-analyses, systematic reviews and randomised trials, then ranked them by study design first, then recency and citations. Retracted papers are removed.

Open a paper to read its abstract and ask for an AI brief of what it found.