Ultraviolet light has long been considered the major cause of most skin cancers, so prevention has focused on staying out of the sun and wearing protective clothing and sunscreen.

But studies in recent years have indicated that several nutritional factors also may play a role, according to Harvey Arbesman, a dermatologist and clinical assistant professor in the departments of Social and Preventive Medicine and Dermatology.

Primary among these factors, Arbesman said, are dietary fat and antioxidant vitamins and minerals.

Half of all new cancers diagnosed in the U.S. are skin cancers. Melanoma, the most serious form of skin cancer, accounts for only about 4 percent of total skin cancers, but is more prone to spreading and can be fatal. The remaining 96 percent are labeled nonmelanoma skin cancers, and they account for an estimated 1 million new cases of skin cancer per year.

Arbesman will review findings of scientific literature dealing with the relationship between nutrition and these nonmelanoma cancers in Orlando tomorrow at the annual meeting of the American Academy of Dermatology and discuss the role of nutritional factors in treating patients at risk.

The majority of nonmelanoma skin cancers are basal cell carcinomas, which rarely spread, but can cause significant local damage that requires surgery, Arbesman said. The remaining nonmelanomas are squamous cell cancers, which pose a slightly increased risk of spreading but are usually easily treated, he noted.

"Clinical trials have demonstrated that a low-fat diet can reduce the development of new precancers called actinic keratoses, as well as basal cell and squamous cell carcinomas," he said. "One recommendation for patients at risk of developing these growths is to consume a diet containing no more than 20 percent of calories from fat."

Risk factors for developing new nonmelanoma skin cancers include a history of precancerous lesions, fair skin, red or blond hair, early severe sunburns and a history of intense sun exposure.

Antioxidant vitamins with the ability to neutralize damaging free-radical molecules produced as a byproduct of normal metabolism and by ultraviolet light have been shown to be potentially important in protecting against skin cancers.

"Some animal and epidemiologic studies have shown that a higher intake of Vitamin C can reduce the development of nonmelanoma skin cancer," Arbesman said. "Another recommendation for persons at risk might be to increase their intake of foods rich in Vitamin C to consume 500 milligrams per day. They also may benefit from increasing their intake of foods containing beta carotene, such as carrots, sweet potatoes and broccoli."

Vitamin E has been shown to reduce the development of ultraviolet light-induced tumors in animals, he reported, but because Vitamin E can interact with other medications, Arbesman cautioned against taking supplements without consulting a physician.

Selenium, a mineral that acts as an antioxidant, also may play a role in reducing the risk of skin cancer. Selenium is available liberally in food sources such as brown rice, whole grains and Brazil nuts. One single Brazil nut provides 120 micrograms of the mineral, exceeding the 100 microgram recommended daily dose, he noted.

Arbesman cautioned against taking selenium supplements because of potential adverse side effects, which include blackened or fragile fingernails, irritability, nausea and vomiting.

"These nutrients that have been shown to have an impact on nonmelanoma skin cancers are already part of most diets, and they benefit other organs as well," he said. "Everyone can benefit from eating more fruits and vegetables.