Scientists are excited about a vitamin again. The vitamin is D, nicknamed the "sunshine vitamin" because the skin makes it from ultraviolet rays. The evidence is strong and keeps growing that sun avoidance may actually cause far more cancer deaths than it prevents.
Harvard professor Edward Giovannucci claims that his research suggests that sunshine-induced vitamin D might prevent much more general cancer cases than it causes skin cancer cases, by a factor of 30 to 1. In the last three months alone, four separate studies found it helped protect against lymphoma and cancers of the prostate, lung and, ironically, the skin. The strongest evidence is for colon cancer.
Animal studies find that vitamin D promotes death of tumor cells. Epidemiological studies find elderly people with low vitamin D tend to get more cancers; black people with black pigments absorbing ultraviolet rays and reducing vitamin D synthesis have more cancers; and people in the North who get less sunshine have more cancers.
Fish oil, particularly fish liver oil, can be a good source for vitamin D, but sunshine is cheap and readily available.