Cancer protection related to solar ultraviolet radiation, altitude and vitamin D.

A whole host of epidemiological studies have reported lower cancer rates and mortality in high-altitude regions. These studies are reviewed and discussed in detail. Evidence for the salutary role of vitamin D in protecting against cancer and other maladies will also be reviewed and discussed. The dependence of vitamin D production on sunlight and its enhancement with altitude will be demonstrated. The hypothesis is advanced and developed that the lower cancer rates observed at high altitudes arise from enhanced sunlight-induced vitamin D production levels. Protective vitamin D mechanisms which support this hypothesis as well as other supportive medical evidence are also presented.