Tea contains chemicals called polyphenols that appear to block the formation of nonmelanoma skin tumors, the researchers say. Unlike sunblock, which prevents the skin from absorbing harmful ultraviolet (UV) light, tea polyphenols work after the skin is exposed to excessive sunlight. The compounds, which are found in both black and green teas, inhibit a newly discovered chemical pathway involving an enzyme called JNK-2 that appears to play a key role in the development of tumors, they say.
The scientists found that the JNK-2 (or "junk-2") enzyme increases after the skin is exposed to sunlight and stays elevated in the skin of those exposed to excess amounts of sunlight. When JNK-2 stays elevated, skin cancers are more likely to develop, they say.
In laboratory studies using mouse models of skin cancer in which the mice were exposed to ultraviolet light, the researchers demonstrated that topical exposure to green tea polyphenols decreased levels of the enzyme, which in turn delays or blocks the skin's response to UV light. Similar polyphenols are also found in black tea.
"We feel this is an important step in improving the prevention of skin cancer," says study leader Dr. Zigang Dong, M.D., a professor at the university and executive director of the school's Hormel Institute. "Topical application of certain tea polyphenols appears to block a key process that leads to skin cancer."
Dong and his research team are currently working to optimize the effectiveness of tea