Green Tea — Best as a Beverage

Many people around the world drink green tea in hopes of warding off cancer, heart disease and immune system ailments. Green tea is a popular beverage throughout much of the world and has been used medicinally for centuries in China and India. In areas where people drink a lot of green tea, there is a lower incidence of heart disease and some cancers.

In recent years, several manufacturers have produced dietary supplements containing highly concentrated extracts of green tea’s active ingredients. The compounds are not toxic in large doses, but high concentrations may not necessarily be healthful.

A study completed by University of Mississippi researchers indicates that extremely high doses of green tea extract actually may activate -- rather than shut down -- genetic mechanisms that help certain tumors survive and grow.

“Drinking green tea still is good for you,” said Yu-Dong Zhou, a molecular biologist at the university’s National Center for Natural Products Research. “There are thousands of years of evidence on that, but the idea of taking the equivalent of hundreds of cups of tea a day is something that needs to be looked at carefully.”

Zhou is principal investigator on a study that examined the effect of high doses of the active ingredients in green tea extract on hypoxia-inducible factor-1, or HIF-1, a key regulator of how tumor cells adapt to low-oxygen conditions. “At low concentrations, it doesn’t seem to have this potentially negative effect as we saw in the lab,” she said. “A lot more study needs to be done to see what the outcome will be in people who take high doses of these compounds.”

“In theory, this effect on HIF-1 could suppress some early forms of tumors but may actually help other tumors -- especially some of the more aggressive ones -- survive and grow,” Nagle said. “We can’t really tell people for sure what will happen when they take these high doses,” she said. “Our best advice is to be careful. This needs to be studied carefully, and it will take time to determine what the actual overall effects are.”

Y-D Zhou et al, “Hypoxia-Inducible Factor-1 Activation by (-)-Epicatechin Gallate: Potential Adverse Effects of Cancer Chemoprevention with High-Dose Green Tea Extracts” , J. Nat. Prod. 2004 67(12); 2063-2069. Material from Newswise was used with permission in the preparation of this article.

As printed in the VHL Family Forum 13:1, April 2005. For permission to reprint, please contact VHL Family Alliance, editor@vhl.org. Further information is available from the VHL Family Alliance, info@vhl.org.