UV radiation and cancer prevention: what is the evidence?

The health benefits of sunlight and the risk of skin cancer from UV exposure are still controversial. The literature was analyzed in terms of reviews, controlled and epidemiological studies for the relationships between sunshine exposure and overall cancer mortality, as well as mortality from cancer of the prostate, colon and breast. The residential and/or occupational sun exposure rate seemed to be positively correlated with a lower risk of overall morality due to organ cancer. A normal vitamin D status appeared to be an important precondition, via the local and autocrine synthesis of 1,25(OH)2D3 in the target tissues. The vitamin D hormone system is necessary for cell proliferation and differentiation; different types of vitamin D receptor gene polymorphism seemed to be associated with cancer cell growth. The health benefits of sunlight appear to outweigh the risk of skin cancer. However, the optimal UV exposure, the target level of circulating vitamin D, and whether vitamin D is the only pathway are still undetermined.