Sunlight, Vitamin D and Skin Cancer

Zittermann A, Prokop S, Armin Zittermann, Sylvana Prokop, Zittermann, Armin, Prokop, Sylvana

In recent years, it became increasingly clear that vitamin D exerts important pleiotropic effects, besides its well-known effects on extracellular calcium homeostasis and on bone metabolism. This article gives a comprehensive overview of studies on cardiovascular and all-cause mortality with a focus on the most recent data. 25-hydroxyvitamin D (25[OH]D) is the best indicator of vitamin D status. Low 25(OH)D levels are highly prevalent among general populations. Prospective cohort studies support the assumption that poor vitamin D status, e.g., 25(OH) D levels below 30 nmol/l, is independently associated with CVD mortality risk. However, support from randomized controlled trials for a beneficial vitamin D effect on CVD risk is still lacking. Meta-analyses of prospective cohort studies indicate beneficial vitamin D effects on overall mortality as well. There is also likely evidence from meta-analyses of randomized controlled trials that vitamin D may improve overall mortality in elderly people. Therefore, it is reasonable to supplement institutionalized individuals and other people with deficient 25(OH)D levels with daily vitamin D amounts of 20 microg. However, it is also noteworthy that prospective cohort studies provide evidence for an inverse J-shaped association between vitamin D status and overall mortality, indicating increased overall mortality risk not only at deficient 25(OH)D levels but also at 25(OH)D levels above 125 nmol/l. Although there is evidence that high 25(OH)D levels sometimes reflect low availability of the vitamin D hormone 1,25-dihydroxyvitamin D, future studies are still needed to clarify the association of high 25(OH)D levels with high mortality rates more detailed.