In groundbreaking research published in the journal Cancer Research, European scientists have determined for the first time why green tea can protect against certain forms of cancer. One of the tea’s active ingredients is a naturally occurring polyphenol called epigallocatechin gallate (EGCG). Researchers found that in vitro, this constituent inhibits cancer cell growth when present at the low concentrations found in the serum and tissues of people who drink two or three cups of green tea per day.

Specifically, EGCG inhibits the activity of dihydrofolate reductase (DHFR), an essential enzyme for making DNA in both normal and tumor cells. Since tumor cells divide more quickly than normal cells and have higher levels of DHFR activity, DHFR is already an established target for anti-cancer drugs.

In fact, the scientists decided to investigate EGCG because they recognized its similarity in structure to the successful anti-cancer drug methotrexate. Turns out, their hunch paid off. Not only does EGCG kill cancer cells, it binds to DHFR less tightly than methotrexate, so it should have decreased side effects on healthy cells. Thus, EGCG could provide the starting point for a new family of anti-cancer drugs.

A note of caution, however: As an enzyme inhibitor, EGCG also is expected to lessen the activity of the enzyme that uses folic acid, minimizing the good effects of folate supplements. If you drink more than two cups of green tea per day, extra folate may be in order.

Did you know?
All tea (except herbal tea) comes from the same plant. Green tea is made from the dried leaves of Camellia sinensis, an evergreen bush native to China and India. The leaves used for green tea are the same as those that make white, black and oolong teas, but they are either steamed or pan-fired right after being picked.

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