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Tea Times - Animal studies suggest tea is a cancer-preventing agent

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Skin and other cancers in mice inhibited by green tea Washington, DC, August 31, 1995 -- Tea appears to act as a cancer-preventing agent in laboratory animals, according to findings presented today at a research conference sponsored by the American Institute for Cancer Research (AICR) on the role of diet in cancer prevention and treatment. These findings provide encouragement in the continuing search for cancer-preventing agents for humans.

In a morning session on the health benefits of polyphenols, some of which are found in tea, Hasan Mukhtar, Ph.D., of Case Western Reserve University cited extensive epidemiological and experimental studies suggesting that green tea may afford protection against certain cancers in certain animal populations. Noting that black tea, which is consumed by 78% of the world's population, may possess similar healthful properties, Dr. Mukhtar said, "In comparison to green tea, the benefits of black tea are less well-studied. Collectively, however, these data provide strong support indicating that black tea may have similar beneficial effects to green tea."

In his review, Dr. Mukhtar demonstrated that polyphenols in green tea appear to effectively afford protection in mice against all three stages of cancer: tumor initiation, tumor promotion and tumor progression. In one series of studies, he reported that green tea administered to mice either topically, or orally in drinking water, resulted in inhibition of skin tumor growth/development. In other studies, administration of green tea resulted in reduced tumor burden that occurs following exposure to ultraviolet-B radiation, the major risk factor for skin cancer in humans. Additional studies using laboratory mice showed that green tea has the property of preventing chemically-induced cancers, including that of the lung, forestomach, esophagus, duodenum, pancreas, liver and colon.

Although research findings in laboratory animals are relevant to human health, Dr. Mukhtar was careful to note that experimental studies on humans have yielded inconclusive results so far. He also reported some recent in vitro data from studies conducted in his laboratory on human prostate cancer cells that indicate green tea polyphenols may afford protection against prostate cancer development. Further studies to define the population which could benefit from tea drinking or by using tea in other edible products are expected.

Existing information suggests that some plant polyphenols may protect against cancer-causing substances by inhibiting the bindings of the genetic material to ultimate carcinogenic substances that may be produced in cells as a result of carcinogenic exposure. Polyphenols may also afford protection against cancer by inhibiting the metabolism of the carcinogenic material.

-Press release from the Tea Council of the USA

Dr. Mukhtar is professor and research director of the Department of Dermatology, the Department of Environmental Health Sciences, the Department of Physiology and Biophysics, and of the Cancer Center at Case Western Reserve University. He is also co-director of the Skin Disease Research Center at Case Western Reserve University. He is an AICR grant recipient.