Daniel W. Cramer and colleagues at Brigham and Women's Hospital in Boston (US) found a dose-related link between women's consumption of coffee and their levels of oestradiol (a naturally occurring form of oestrogen) during the first five days of their menstrual cycle. The study included nearly 500 women aged 36 to 45 who were not pregnant, breast-feeding or taking hormones.

They recommend any woman with endometriosis, breast pain or family histories of breast or ovarian cancer, especially arising premenopausally, to limit consumption to two cups a day. Raised oestrogen levels have been linked with all of these female diseases.

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