For the millions of Americans, warnings about the carcinogenic effects of excessive sun exposure have come too little or too late.

But a panel of dermatology experts report that a number of common topical and edible agents are now being tested for their ability to slow or prevent the onset of disease among those already overexposed to ultraviolet (UV) radiation.

Tanning "is a protective maneuver by your body in response to skin damage, so there is no 'safe' tan," stressed panel speaker Dr. James M. Spencer. "But for those who didn't know any better...there are many steps between overexposure to the sun and developing skin cancer, and so there are many places we could intervene to stop the process."

As director of the division of Dermatologic Surgery at the Mount Sinai School of Medicine in New York City, Spencer reviewed the latest advances in "chemoprevention" -- the clinical term for the inhibition and reversal of the aging process and cancer brought on by UV radiation. Experts estimate that more than 1 million new cases of skin cancer will be diagnosed in the US this year.

Spencer highlighted one recent study that found a 5-year regimen of oral vitamin A significantly reduced the formation of certain types of skin cancer cells among almost 2,300 patients who had a history of precancerous skin abnormalities and were at moderate risk of full-blown skin cancer.

The researcher pointed out, however, that potentially serious side effects such as liver inflammation and elevated cholesterol levels make vitamin A a less-than-ideal treatment, and that those at very high risk of skin cancer did not seem to benefit.

But Spencer added that other research is focusing on the link between diet and cancer prevention, with green tea and soybeans standing out as two of the most promising foods. He noted that certain antioxidants in green tea -- the second most widely consumed beverage in the world after water -- and certain isoflavones found in soy products seemed to stop the growth of tumors in early animal studies.

Other preliminary findings suggest that a diet low in fat, or higher in unsaturated fat than saturated fat, may also result in fewer skin tumors, he said. Even aspirin and over-the counter nonsteroidal anti-inflammatory medicines appear to have chemopreventative effects, Spencer added.

Since it can take 10 to 20 years for the effects of sun damage to appear on the skin, these new treatments may in the long run prove to be lifesavers following sun exposure, Spencer told Reuters Health. But he cautioned that research is ongoing and inconclusive to date, so consumers should not to hastily embark on any vitamin or food program -- particularly those with side effects.

"As long as it's a trivial intervention such as incorporating soy in your diet, then it may very well be helpful, but vitamin A would not be since it has serious side effects," he said. "Green tea belongs in the lab at this point," he added. "It's a maybe. It's certainly not proven. This is an exciting horizon for the future -- but we're not there yet."