We frequently get warnings against too much sun exposure and are cautioned to use sun block and to cover up, but being in the sun may actually protect against some cancers. While overexposure and sun burn can increase the risk of skin cancer, some exposure to the sun is good.

A study appearing in the July-August, 2006 issue of Anticancer Research, suggests that a reduced risk for cancer in several locations is associated with sunlight (ultraviolet B). Exposure to the sun increases vitamin D production. Vitamin D is known to protect against cancer; it inhibits blood supply to the tumor and inhibits metastasis.

The lead author of the study, Dr. William Grant, recommends vitamin D supplementation (1,000-1,500 IU per day), and moderate exposure to the sun (15 minutes, 3x per week for a fair-skinned person, more for dark-skinned individuals). Both the supplementation and the sun exposure are still controversial. One study, appearing in the New England Journal of Medicine (2006;354:684-696) was not very favorable for vitamin D supplementation as a cancer preventative. Dr. Williams points out that the study only used 400 IU of vitamin D and that a higher dose would be more effective. This echoes a common criticism that medical research done on natural substances is frequently designed to fail.