Cancer Prevention

Evidence of vitamin D's protective effect against cancer is compelling. For more than 50 years, documentation in the medical literature suggests regular sun exposure is associated with substantial decreases in death rates from certain cancers and a decrease in overall cancer death rates. Recent research suggests this is a causal relationship that acts through the body's vitamin D metabolic pathways. For instance, some evidence points to a prostate, breast and colon cancer belt in the United States, which lies in northern latitudes under more cloud cover than other regions during the year. Rates for these cancers are two to three times higher than in sunnier areas.¹

Dark-skinned people require more sun exposure to make vitamin D. The thickness of the skin layer called the stratum corneum affects the absorption of UV radiation. Black human skin is thicker than white skin and thus transmits only about 40 percent of the UV rays for vitamin D production. Darkly pigmented individuals who live in sunny equatorial climates experience a higher mortality rate (not incidence) from breast and prostate cancer when they move to geographic areas that are deprived of sunlight exposure in winter months. The rate of increase varies, and researchers hesitate to quote figures because many migrant black populations also have poor nutrition and deficient health care that confound statistics somewhat.²

Although excessive sun exposure may give rise to skin cancer, researchers as early as 1936 were aware that skin cancer patients have reduced rates of other cancers. One researcher estimates moderate sunning would prevent 30,000 annual cancer deaths in the United States.³

Vitamin D may also go beyond cancer prevention and provide tumor therapy. Much ado has been made of pharmaceutical angiogenesis inhibitors--agents that help inhibit the growth of new, undesirable blood vessels that tumors require for nutrient supply and growth. Laboratory tests have shown vitamin D to be a potent angiogenesis inhibitor.⁴

Vitamin D also works at another stage of cancer development. Tumor cells are young, immortal cells that never grow up, mature and die off. Because vitamin D derivatives have been shown to promote normal cell growth and maturation, drug companies today are attempting to engineer patent able forms of vitamin D for anti-cancer therapy.⁵