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Wednesday 20th June 2018

Green tea does not protect against cancer

2nd November 2010

A new Japanese study has shown that there is no demonstrable link between the consumption of green tea and breast cancer.


The findings suggest that the hot drink, which has been linked to many other health benefits, does not protect women against breast cancer, in spite of being rich in antioxidants.

The study's conclusion contradicts previous research on both animals and human cells that suggested green tea could boost anti-cancer defences in the human body.

In a five-year analysis of 54,000 women, researchers at the National Cancer Centre in Tokyo said they found no association between drinking green tea and breast cancer risk.

Study lead author Motoki Iwasaki said that previous studies on the effects of green tea on breast cancer risk in humans had been inconclusive.

But he said his team had conducted a large-scale, population-based prospective cohort study, which was one of the first to include a wide range of tea intakes.

He said the study differentiated between women who drank less than one cup of green tea per week and those who drank 10 or more cups a day.

He said the team found no overall association between green tea intake and the risk of breast cancer.

Published in BioMed Central's open access journal Breast Cancer Research, the study assessed tea intake by a questionnaire, once at the beginning of the study and then again five years later.

It relied on notifications from major local hospitals in the area of the study, along with population-based cancer registries, to determine which women were eventually diagnosed with breast cancer.

The popularity of green tea as a beverage in Japan provided a large number of tea-drinking participants.

While around 12% of women drank less than one cup of green tea per week, 27% drank five or more cups per day.

Iwasaki said that another strength of his study was its prospective design, in which information was collected before the subsequent diagnosis of breast cancer.

In this way, the exposure recall bias inherent to case-control studies was avoided, he said.

The researchers concluded that drinking green tea as a beverage was unlikely to reduce the risk of breast cancer, regardless of green tea type and the number of cups consumed.

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