A new study has reported that women who consume at least six cups of coffee per day have a lower risk of breast cancer, and estrogen receptor negative (ER-) disease in particular, than those who drink an average of one cup per day or fewer. There is evidence that differences exist in the associations between coffee consumption and breast cancer risk depending on hormone receptor status. The study was conducted among Swedish women, who have a higher rate of coffee consumption than U.S. women, generally speaking. Included were a total of 2,818 postmenopausal breast cancer cases and 3,111 cancer-free controls. Coffee intake was determined using food recall questionnaires.
Coffee consumption was found to be associated with a 20% reduction in overall breast cancer risk in an age-adjusted model when comparing heavy with light drinkers (i.e., those consuming at least six cups per day compared to those who drank one cup per day or fewer). An over 50% reduction in the risk of ER- breast cancer was found in heavy compared to light coffee drinkers. The authors conclude that high daily intake of coffee is associated with a decrease in ER- breast cancer among postmenopausal women.
Previous studies have reported mixed results
Taken by themselves, the study results appear definitive, but they are not supported by most previous study findings, including major prospective studies among Swedish women. The effects of coffee on breast cancer risk are probably the result of a combination of factors, including genetic differences among women. Coffee consumption is not recommended for women with fibrocystic breast disease, since it has been associated with higher risk of ER- breast cancer. On the other hand, heavy consumption of coffee has been associated with significantly reduced breast cancer risk among women with BRCA1 or BRCA2 gene mutations. There is some evidence that high coffee consumption might increase breast cancer risk among premenopausal women. The bottom line is that modest coffee consumption does not appear to effect breast cancer risk in most women. We would not recommend that women with ER- breast cancer take up heavy coffee drinking based on the study results - there are more effective dietary strategies. Please see our articles on coffee and what triple negative patients and survivors should eat breast cancer.
Please see our article on how to optimize your breast cancer diet for information on what to eat during all stages of treatment and recovery.