When you live in a sunny climate (like I do), your risk of colon cancer and other cancers drops. Scientists from Johns Hopkins University credit this phenomenon to possibility that greater serum levels of vitamin D is responsible. But don't start thinking of joining me in Arizona just yet. Skin cancer risk skyrockets here.
Mohr SB. A brief history of vitamin d and cancer prevention. Ann Epidemiol 2009;19:79-83.