A new prospective study has reported that coffee drinking does not appear to influence the risk of hormone receptor positive (ER+/PR+) or negative (ER-/PR-) breast cancer among women 50 and older. The study was designed to investigate the association between coffee consumption and breast cancer risk according to hormone receptor status. Plausible biologic mechanisms exist whereby coffee or its components could reduce risk of breast cancer. Caffeine has been reported to suppress mammary tumor formation in animal models of breast cancer. Caffeic acid, another coffee component, has been shown to inhibit breast cancer development. Coffee could also reduce breast risk by reducing inflammation and altering estrogen metabolism. However, population study results have been inconsistent and few studies have examined the association by estrogen receptor and progesterone receptor status.

To conduct the study, the authors analyzed data from the NIH-AARP Diet and Health Study, which included 198,404 initially cancer-free women aged 50 to 71 years. Most of these women were postmenopausal. Participants filled out a questionnaire during 1995 or 1996 that captured usual coffee intake over the previous year.

A total of 9,915 cases of breast cancer were identified through December 2006 among the women enrolled in the NIH-AARP Diet and Health Study. There were 2,051 ER+/PR+ and 453 ER-/PR- cancers identified among participants for whom hormone receptor status was available. Coffee intake was not found to be associated with breast cancer risk, when comparing women who drank at least four cups per day with those who never drank coffee. The findings did not vary by body mass index (BMI) or history of benign breast biopsy. No evidence of a relationship with either caffeinated or decaffeinated coffee was found. The authors conclude that coffee did not appear to influence the risk of hormone receptor positive or negative breast cancers among study participants.

Comments regarding the study

Coffee drinking has variously been reported to have either a small positive or negative association with breast cancer risk, or no association at all, in the general population. However, the body's reaction to coffee can vary for different women based on genetic differences and other factors. For example, coffee has been reported to increase the risk of breast cancer among women with benign fibrocystic breast disease and reduce it among BRCA mutation carriers.

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.