Researchers in the US are developing a new cream composed of compounds found in tea, which they claim will help fight skin cancer, the most common type of cancer in the United States. Early animal tests on the lotion are promising, said the researchers, presenting their work yesterday at an American Chemical Society meeting.
The polyphenols in tea, also found in wine and chocolate, appear to block the formation of non-melanoma skin tumours, reported the researchers from the University of Minnesota in Austin. 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 inhibit a newly discovered chemical pathway - involving an enzyme called JNK-2 - that appears to play a key role in the development of tumours. 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, explained the scientists.
In studies on mice that had been exposed to ultraviolet light, 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," said study leader Dr Zigang Dong, a professor at the university and executive director of the school's Hormel Institute.
Human testing of the proposed skin cream could begin in a few years, he added. Dong's team are currently working to optimise the effectiveness of tea components against cancer. Designed to be applied after exposure to excessive sun, the skin cream could be used alone or combined with sunscreen to help maximise cancer protection.
It is not yet known if the tea chemicals will inhibit melanoma, the least common but most deadly type of skin cancer. Previous research has found that drinking tea, particularly green tea, may be effective against skin cancer. This is thought to be due to tea's high level of antioxidants, which destroy free radicals that can trigger the cancer process. The much-studied popular drink has also been found to fight colon and bladder cancer, protect heart health and fight allergies and the onset of arthritis.
"Drinking tea may help, but you'd have to drink a large amount to accumulate in the skin, perhaps as many as 10 cups a day. It's easier to concentrate it in a cream form, and it's probably more effective," said Dong.
The research, presented yesterday during a Tea and Health symposium at the ACS meeting, followed findings by Japanese researchers that a green tea extract significantly reduced body fat when fed to mice daily over several months. The extract, which seems to inhibit the absorption of fats and starches, is being developed into a pill or drink that the scientists hope will have a similar fat-fighting effect in people.
Another paper looked at its ability to reduce the risk of mouth cancer in smokers. In a small pilot study on human subjects, the researchers found that drinking five cups of green tea daily over a four-week period significantly reduced DNA damage in the mouth cells of smokers, reducing their likelihood of developing precancerous lesions and ultimately cancer.