Vitamin D — Baseline Status and Effective Dose

There has been more ink spilled over the efficacy of vitamin D than over that of most nutrients, with the possible exception of sodium. Why is this? Dozens of randomized, controlled trials have been conducted — some large, and many small. Unfortunately, their results have been inconsistent — some positive, some null, and the odd one or two actually negative. Even the many available meta-analyses on the topic have yielded inconsistent results. If vitamin D is actually efficacious, why is there this inconsistency?In this issue of the Journal, in yet another meta-analysis, Bischoff-Ferrari et al.1 suggest several explanations, including . . .