The study, published in Nutrition Journal, assessed the possible association between green tea intake and urinary oestrogens and oestrogen metabolites – finding that a high intake of green tea can modify oestrogen metabolism or conjugation “and in this way may influence breast cancer risk.”
Led by Dr Barbara Fuhrman from the National Cancer Institute at the United States National Institutes of Health, the research team followed nearly 200 pre-and postmenopausal women to assess the effect of green tea on oestrogen metabolism, which is a known known causal factors in the development of breast cancer.
Fuhrman and her colleagues found that daily consumption of green tea was associated with lower levels of oestrogen metabolites, which they suggested could be explained by the fact that polyphenols found in green tea can influence enzymes that metabolise oestrogens.
“Among postmenopausal Japanese American women, we observed that more frequent intake of green tea was associated with reduced urinary concentrations of oestrone,” said the researchers.
“As a rich source of phytochemicals that can interact with and regulate xenobiotic metabolising enzymes, green tea may modify metabolism or conjugation of oestrogens and may thereby impact breast cancer risk,” they suggested.
As a result, Fuhrman and her team suggested that randomised feeding studies will now be helpful in establishing the mechanisms by which green tea may modulate cancer risk.