Roles of Solar UVB and Vitamin D in Reducing Cancer Risk and Increasing Survival.

The present article reviews existing scientific evidence in support of the ultraviolet-B (UVB)-vitamin D-cancer hypothesis, now being in its 35th year. Literature evidence comes from geographical ecological and observational studies, two successful clinical trials, and an understanding of how vitamin D reduces risk of and increases survival from cancer. Each approach has its strengths and limitations, and considering findings from all of these approaches yields the best conclusions. There exist over 15 types of cancer for which UVB exposure and/or 25-hydroxyvitamin D [25(OH)D] concentrations have been found associated with reduced risk. The optimal 25(OH)D concentration for preventing and surviving cancer appears to be above 75-100 nmol/l. There exists mounting evidence that individuals with higher 25(OH)D concentration at the time of cancer diagnosis have better cancer-specific and overall survival rates, suggesting that cancer-affected people should raise their 25(OH)D concentrations.