Green tea found having little breast cancer prevention effect

Heavy intake of green tea was found to have little effect in reducing the risk of contracting breast cancer, contrary to common belief, according to a report released Thursday by the National Cancer Center.

As there was little difference in terms of the degree of risk between those who drink little green tea and those who drink more than 10 cups a day, "we cannot expect breast cancer prevention effect from the intake of green tea," said Motoki Iwasaki, section head of the Epidemiology and Prevention Division at the center.

Although animal tests have shown that catechin and other polyphenols contained in green tea are possibly effective in preventing breast cancer, epidemiology studies on human beings have produced varying results, according to the center.

The center had conducted tracking research since 1990 and 1993 over an average span of 14 years targeting some 54,000 women aged 40 to 69 in nine prefectures. Among them, 581 women developed breast cancer during the period.

In comparing the survey results, the center divided the women into six groups in terms of how often they drank green tea -- from less than one cup a week to more than five cups a day.

The findings showed no clear correlation between the frequency of drinking green tea and breast cancer development, the report said.

Of the 54,000 women, the center performed detailed analysis on about 44,000 over a period of some 10 years by subdividing frequent drinkers.

Even among those who habitually take green tea, including those who drink seven-nine cups or more than 10 cups a day, there was no correlation, the report showed.

The difference in the quality of the leaf, such as medium-grade and coarse-grade, did not affect the risk of developing cancer either, according to the report.

source: japan_now