Academic journal article Environmental Health Perspectives

Temperance in Green Tea

Academic journal article Environmental Health Perspectives

Temperance in Green Tea

Article excerpt

Throughout China and Japan, green tea is considered a staple beverage. Many epidemiologic studies have linked frequent tea intake with a lower incidence of cancer, cardiovascular disease, and neurodegenerative disorders. Consumer interest in the tea's health benefits has led to the inclusion of green tea extracts in multivitamins and other dietary supplements. But too much of a good thing could prove harmful, according to a review in the April 2007 issue of Chemical Research in Toxicology that analyzed the toxic potential of green tea polyphenols.

Currently there are no published epidemiologic studies on the toxicity of green tea supplements. But laboratory research with both rodents and dogs has shown that high doses of the most heavily studied green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG), cause liver, kidney, and gastrointestinal toxicities.

Case reports on the toxic effects of green tea extracts in humans are also beginning to emerge. "To date, there have been nine anecdotal case reports of liver toxicity in humans associated with consumption of high doses [700-2,000 mg/day] of green tea from dietary supplements," says lead author Joshua Lambert, an assistant research professor in the Department of Chemical Biology at Rutgers University. "In some cases, the subject stopped taking the supplement and the symptoms resolved, and then the subject started taking the supplement again and liver toxicity returned." Such observations, albeit anecdotal, suggest that green tea supplements are not without risk.

Cell culture studies have shown that EGCG can cause oxidative stress, although these data now need to be confirmed in animal models. The Rutgers team speculates that some susceptible individuals may carry a particular polymorphism of the gene that codes catecholamine-o-methyltransferase, an enzyme critical to the protection of cells against EGCG-mediated oxidative stress and hepatotoxicity. …

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