Vitamin D supplements and disease prevention: Neglect or good practice? Authors' reply to letters by Rhein and Degner

We wonder what compelled Rhein to accuse us of “condescending neglect” of northern Britain, especially given that one of us lives in northeast Scotland. She says that the evidence for vitamin D supplements is good enough for her, citing meta-analyses of randomised trials for patients in critical care, cancer mortality, and asthma. But these meta-analyses have substantial limitations that led their authors and authors of similar contemporaneous reviews to call for more trials, not for changes to clinical practice. The other evidence that she cites is from observational studies or studies with surrogate endpoints, which are insufficient to inform clinical practice.

Arguably the best evidence for whether people at risk of vitamin D insufficiency in northern Britain should take supplements is from the RECORD trial. This large trial of older adults from 21 sites across England and Scotland showed that 800 IU daily of vitamin D had no effect on total or hip fractures, falls, cardiovascular or cancer mortality, infections, preventing diabetes, or the need for more diabetic medication. Furthermore, no evidence was found for a differential effect of vitamin D supplementation according to latitude, with 1636 of 5292 participants recruited in Scotland.