Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational studies and randomised trials.

Researchers reviewed 107 systematic reviews, which combine results from many health studies, including trials and observational studies. They examined vitamin D levels or vitamin D supplements in relation to many outcomes, such as cancer, heart disease, diabetes, fractures, falls, and death. Low vitamin D levels were often linked with worse health, but this does not prove that low vitamin D caused those problems. In supplement trials, benefits were generally small or absent, with the clearest possible benefit being fewer falls in some older people, especially when vitamin D was taken with calcium.

What this means for you: This review does not support buying vitamin D as a general protection against disease or aging. Supplements may help people who are deficient or at particular risk, but the evidence for broad benefits is inconsistent.