NEW YORKA 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
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
sunscreenit 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.