Role of Vitamin D for Cardiovascular Health.

The prevailing medical opinion up to the 1960s held that vitamin D was a risk factor for cardiovascular disease, arising from research showing that megadoses of vitamin D caused arteriosclerosis in animals. However, the development of competitive protein-binding assays for 25-hydroxyvitamin D [25(OH)D] in the 1970s showed that only a small proportion of body vitamin D comes from diet, with more than 80% synthesized from sun exposure. A 1981 review of the epidemiology, which found that cardiovascular disease rates increased in winter with increasing latitude and were reduced at high altitudes, led to the hypothesis that ultraviolet radiation, by increasing vitamin D levels, protects against cardiovascular disease. Since then, observational epidemiological studies have reported inverse associations between serum 25-hydroxyvitamin D levels and risk of cardiovascular disease. However, randomized clinical trials are required to confirm that vitamin D protects against cardiovascular disease. Several mechanisms have been proposed for the putative protective effect of vitamin D against cardiovascular disease. These include beneficial changes in cardiac function, blood pressure (including endothelial function), insulin resistance, and inflammatory processes. [ABSTRACT FROM AUTHOR]