As a green tea devotee, I feel a glow of good health whenever my favorite hot beverage is lauded for its wellness-boosting properties. Rich in polyphenol antioxidants, green tea is said by some to protect against heart disease and cancer, as well as to supply other health perks. But new research provides a reminder that not all of green tea's purported goodness is steeped in strong evidence.
The study explored whether drinking green tea can reduce the risk of breast cancer. This theory is rooted partly in the fact that green tea is consumed widely in Japan and other Asian countries that have lower rates of breast cancer. Animal and laboratory studies have also suggested that green tea may inhibit the growth of cancer cells.
In the new study, researchers looked at data on nearly 54,000 middle-aged women in Japan. Over five years, the participants completed two detailed questionnaires asking about their health, lifestyle, and diet, including their consumption of green tea. The researchers then tracked who developed breast cancer. On average, the study followed the women for 13.6 years.
The researchers found no difference in breast cancer risk based on how much green tea the women drank. Those who consumed five or more cups a day were just as likely to develop breast cancer as those who drank less than one cup per week.
These findings are striking. But this type of study can't prove that green tea has no effect on breast cancer risk. And since the study included only Japanese women, we can't be certain that these findings apply to other groups. For example, it's possible that green tea might have a different effect in women of other ethnic backgrounds, or with different diets.
Even so, it provides a reminder that when it comes to health benefits, be cautious about reading too much into the green tea leaves.
What you need to know. If you drink green tea, you should do so primarily because you enjoy it, not because you expect it to lower your risk of breast cancer or another disease. As this study illustrates, not all the health benefits attributed to green tea are certain.
—Sophie Ramsey, patient editor, BMJ Group
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