NEW YORK—A variety of simple dietary interventions could prove effective in inhibiting carcinogenesis and reducing the incidence of skin cancers, said James M. Spencer, MD, associate professor of dermatology, Mount Sinai School of Medicine, New York.

"Chemoprevention is a big research area, not just for skin cancer, and I think in the next few years, we’ll see many promising new candidates emerge," Dr. Spencer said at an American Academy of Dermatology (AAD) press conference.

In the setting of skin cancer, chemoprevention has already been demonstrated for vitamin A in relation to squamous cell carcinomas in moderate-risk populations, while vitamin A derivatives have proven effective for certain high-risk populations, Dr. Spencer said. However, he noted, long-term use would be limited by skeletal toxicity and other potential side effects. Other promising but less-toxic dietary approaches are under study now.

Research dating back to 1939 suggests that animals fed high-fat diets may be more susceptible to skin cancers, he said. More recently, a study found a relatively protective effect against UV-induced squamous cell carcinoma among mice fed a constant percentage of unsaturated fats vs mice fed saturated fats.

In one human study, patients with a history of nonmelanoma skin cancer went on a low-fat diet (20% of total calories) and were compared to a control group (38% of calories). At 2 years, there was a significant reduction in new skin cancers in the low-fat group, "although it is hard to get your fat content down to 20%," Dr. Spencer observed.

Vegetables, Grain, and Green Tea

Nutrients or non-nutrients (ie, trace elements such as selenium) in the diet may alter susceptibility to UV-induced skin cancers, he said. Research has shown that mice fed a crude diet of vegetables and grain have a lower liver cancer incidence than mice fed a semipurified diet.

Epigallocatechin-3-gallate (EGCG), a polyphenolic antioxidant found in green tea, has been of interest to researchers and health-food store customers. In mice, EGCG given topically or orally inhibits UV-induced skin cancer, he said.

Diets rich in soybeans have been associated with a lower incidence of breast, prostate, liver, and other cancers, he commented. In animal studies, high-soybean diets inhibited skin and other tumors induced by radiation or carcinogen.

Isoflavones have emerged as the leading potential protective candidate in soybeans. Genistein, the most potent of these phytochemicals, was shown in a Mount Sinai study of nude mice to be potentially effective for prevention of UV-induced carcinogenesis and sunburn. "Genistein is not a sunscreen—it does not block ultraviolet light; rather, it works later in the carcinogenic process," he said.

While entrepreneurs tout the purported health benefits of green tea and soybeans, the findings related to UV-induced carcinogenesis "belong in the laboratory at this point," Dr. Spencer said. "It’s an exciting research area, but certainly not proven, and they’re not even sure, exactly, which component of green tea might have this effect." That said, Dr. Spencer commented that higher-risk patients would now be candidates for "trivial" interventions, such as addition of soybeans to the diet, based on research findings to date, particularly if the intervention is cheap and carries little to no risk of long-term side effects.