Blocking skin cancer through diet?

Add yet another disease to the list of those from which a low-fat diet may be able to save you: skin cancer. Eating less fat than Americans generally do considerably reduces the risk of developing precancerous spots on the skin, according to a preliminary study from Houston, Texas.

Researchers there monitored the skin health of some six dozen men and women, all of whom had already suffered at least one bout of skin cancer. Half of them cut their fat intake from the typical American average of about 40 percent of calories to roughly 20 percent. The other half continued to follow their usual diets. At the end of two years, the higher-fat eaters developed an average of 10 new premalignant spots, or lesions, each. Those who had adopted the lower-fat regimen, however, averaged only about three new precancerous lesions each.

The lesions, which may be tan or brownish in color, are not the little dots that are commonly referred to as aging or liver spots. Rather, they are rough, dry, scaly bumps that measure anywhere from one-quarter inch to an inch in diameter and may also be colored red or grayish. Technically known as solar keratoses, these bumps rank as the most common precancerous skin condition, affecting more than five million Americans, frequently over age 60 and frequently with fair rather than dark skin. They show up most often on the face, lower lip, back of the hands, forearms, scalp of bald men, and neck. And they have anywhere from a one to 25 percent chance of developing into a type of skin cancer called squamous cell carcinoma if a physician does not remove them.

To be sure, squamous cell carcinoma is not among the more serious types of skin cancer. The cure rate is extremely high--95 percent when detected and treated early. In some cases, however, the cancer can metastasize (spread) to other parts of the body and prove fatal.

The researchers aren't sure, incidentally, why cutting down on fat in the diet would inhibit the development of precancerous growths that sometimes lead to squamous cell carcinoma. One theory, says head investigator Homer Black, PhD, is that lower levels of dietary fat may lead to lower levels in the body of substances that regulate immune function, such as prostaglandins. In higher concentrations, those substances could pave the way for inflammations and possible tumor formation.

Whatever the potential mechanism, it is important not only to eat a low-fat diet but also to avoid excessive sunlight--or at least wear sunscreen with a protection factor of 15. Unlike diet, too much sunlight is a known risk factor for solar keratoses and skin cancer alike.

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