Sunlight

Sunlight Actually Prevents Cancer

Insufficient exposure to ultraviolet radiation may be an important risk factor for cancer in Western Europe and North America, according to a new study published in the prominent Cancer journal that directly contradicts official advice about sunlight.

The research examined cancer mortality in the United States. Deaths from a range of cancers of the reproductive and digestive systems were approximately twice as high in New England as in the southwest, despite a diet that varies little between regions.

An examination of 506 regions found a close inverse correlation between cancer mortality and levels of ultraviolet B light. The likeliest mechanism for a protective effect of sunlight is vitamin D, which is synthesized by the body in the presence of ultraviolet B.

The study's author, Dr William Grant (wbgrant@infi.net) , says northern parts of the United States may be dark enough in winter that vitamin D synthesis shuts down completely.

While the study focused on white Americans, the same geographical trend affects black Americans, whose overall cancer rates are significantly higher. Darker skinned people require more sunlight to synthesize vitamin D.

There are 13 malignancies that show this inverse correlation, mostly reproductive and digestive cancers. The strongest inverse correlation is with breast, colon, and ovarian cancer.

Other cancers apparently affected by sunlight include tumors of the bladder, uterus, esophagus, rectum, and stomach.

Cancer March 2002; 94:1867-75