Biomedical Frontiers: Fall 1996, Vol.4, No.1
A Tea-Skin Cancer Connection

Can the pigments in tea protect against sunburn and skin damage that leads to cancer? Dr. Zhi Yuan Wang, research scientist in the department of dermatology, is aiming to find out.

Ten years ago the suggestion that tea could prevent cancer would have made Dr. Wang laugh: At the time, epidemiological studies linked tea drinking to cancer of the esophagus. Seeking to find further proof of that conclusion, Dr. Wang emigrated from his native land, China, in 1986 to work under Dr. David Bickers, then chairman of dermatology at Case Western Reserve University.

Today, Dr. Bickers is chairman of dermatology at P&S, and Dr. Wang is still pursuing the tea-cancer connection. In the intervening years, Dr. Wang has been a leading researcher in uncovering evidence that tea can prevent cancer in experimental models. (The connection to esophageal cancer was disproved when further studies found that hot drinks--not tea--were the cause. Furthermore, in 1995 Dr. Wang published a paper that showed tea prevented nitrosamine-induced esophageal cancer in rats.)

Dr. Wang was the first scientist to demonstrate that treatment with tea extracts could protect animals against ultraviolet (UV) light-induced skin carcinogenesis. Subsequent preliminary studies have shown that topical and ingested doses of either green or black tea extracts protect against sunburn and skin cancer induced by sunlight.

According to Dr. Wang, it makes sense that tea--and, indeed, many other plants and flowers--should contain a photo-protective chemical. "Plants are exposed to DNA-damaging UV light, so we believe that it is likely that plants should have their own sun protection system," he says. "Polyphenols in tea--specifically, flavonoids--may be the chemical that provides this protection." For instance, tea that grows in the mountains is exposed to more UV light than other tea and is also richest in polyphenols. (And, perhaps not coincidentally, mountain-grown tea is considered to have the best flavor.) The enzyme tyrosinase converts flavonoids in green tea to black tea pigment. In humans, tyrosinase is a key enzyme that converts tyrosine to melanin pigments.

"Plants are exposed to DNA-damaging UV light, so we believe that it is likely that plants should have their own sun protection system."

Dr. Wang plans to identify the specific components of tea that provide sun and cancer protection and to pursue studies addressing their mechanisms of action. Eventually, if all goes well, researchers plan to conduct clinical trials on the effectiveness of tea, both as a topical agent and as a beverage, against sunburn and skin cancer.