[Vitamin D: evidence and controversies]

Vitamin D enhances musculoskeletal health and reduces mortality related to bone disease in some populations, particularly the elderly and other high-risk groups. Evidence suggests that vitamin D has an impact in cancer, cardiovascular disease, autoimmune processes, and infections. Epidemiologic studies have also detected vitamin D deficits or insufficiency in nearly all the world's populations. Such evidence has led to debate related, to a certain degree, to photoprotective measures that aim at protecting against skin cancer. The latest recommendations of the American Institute of Medicine consider that serum levels of 20 ng/mL (50 nmol/L) appear to be adequate in the general population and achievable even with minimal sun exposure. If these figures are reliable, the apparent pandemic of vitamin D deficiency reported in recent years may be exaggerated. This article reviews the evidence and issues under discussion, looking especially at the role ultraviolet radiation plays in synthesizing vitamin D in the skin. The conclusion is that sun exposure should not be used as the only source of vitamin D given that it is also clearly carcinogenic for the skin. A healthful approach combines moderate sun exposure, adequate food sources of the vitamin, and supplements whenever required.