Ultraviolet B, vitamin D and their mechanisms in cancer prevention

Background: Recent advances confirming the role of vitamin D in prevention of cancer have created a new field of scientific interest. The main source of vitamin D is exposure of the skin to ultraviolet light, and characteristics that reduce penetration of ultraviolet B (UVB) through the atmosphere play a major role in increasing risk of cancers of the colon, breast, and other sites. Objective: The objective of this project was to systematically review all epidemiological and laboratory studies concerning effects of UVB or vitamin D on colon and breast cancer. Methods: All published research articles identified in computer sources as measuring the role of ultraviolet B vitamin D, and its metabolites in conjunction with colon and breast cancer were ascertained and abstracts or articles were reviewed. Epidemiological studies and experiments were examined and results were combined into summaries when possible. Results: The preponderance of epidemiological and laboratory studies support the hypothesis that moderate exposures to ultraviolet B and vitamin D provide important protection against colon and breast cancer, among others. The effect is present throughout life for colon cancer, but is exerted mostly during the first two decades of life for breast cancer. Conclusion: At latitudes above approximately 37degrees, climatological factors, sulfate air pollution, stratospheric ozone, and behavioral factors combine to reduce the dermal synthesis of vitamin D to virtually zero during winter months. These populations are therefore at markedly elevated risk of vitamin D deficiency, and, consequently, of colon and breast cancer incidence and mortality.