A paper entitled “Effects of vitamin D supplementation on musculoskeletal health: a systematic review, meta-analysis, and trial sequential analysis” was recently published in Lancet. The authors identified 51 randomized control trials (RCT) with high- and low-dose vitamin D supplementation. They concluded:
Full disclosure, because of Nature’s paywall I have not read the paper in detail. However, it is my strongly held position that meta-analyses which only evaluate nutrient supplementation miss the point. It is clearly established that essential nutrients, e.g. vitamins, EPA+DHA, lutein, zeaxanthin, iron, etc, provide benefit when nutrient status is insufficient to support normal cell structure and function.
Food fortification is known to improve nutritional status, help prevent deficiency diseases and save lives. This fact isn’t based on dietary intake data. It is based on status measurements and health outcomes, e.g. effect of mandatory folic acid fortification of flour in incidence of neural tube defects.
So, with input from Dr William B Grant (@wbgrant2), here is evidence (4 examples) that it is vitamin D status, i.e. 25(OH)D3 concentrations, which is correlated with outcome and needs to be measured NOT whether an individual is randomized to a supplement or placebo arm of a RCT.
Maternal 25(OH)D3 status and Gestational Age (weeks