Vitamin D and the heart: why we need large-scale clinical trials.

Although vitamin D supplementation appears to be a promising intervention for reducing risks of cancer, cardiovascular disease, and other chronic diseases, existing evidence on its benefits and risks is limited and inconclusive. Recruitment is now under way for the Vitamin D and Omega-3 Trial (VITAL), the first large-scale randomized clinical trial of these nutritional agents for the primary prevention of cancer and cardiovascular disease.