Increasing data suggest that many or most adults in the United States and Europe would benefit from vitamin D supplements. This review summarizes the benefits of vitamin D with the strongest evidence today from randomized controlled trials for fall and fracture prevention. Beyond fall and fracture prevention, vitamin D may also reduce overall morbidity by multiple mechanisms. Prospective epidemiological studies supported by strong mechanistic evidence suggest a reduction of cardiovascular disease (incident hypertension and cardiovascular mortality) and colorectal cancer, extending to weaker evidence on immune-modulatory and anti-inflammatory benefits of vitamin D.