I got the news last week, I even heard it on NPR, that coffee drinkers, men at least, had fewer prostate cancers. BUT, what about women and breast cancer. Let's look at the data.
A paper, published online 11 May 2011 in Breast Cancer Research, a peer-reviewed publication, can be found at http://www.breast-cancer-research.com/content/13/3/R49 does give us some data and good news for coffee drinkers. Despite the fact that coffee has been the subject of many studies, we are just now beginning to understand the relationship between coffee intake and breast cancer. A large meta-analysis of over 500 reports (Nutr Cancer2010,62:271-283) suggested no clear cut association of coffee consumption and breast cancer risk, in general. Nevertheless, several other reviews, including Nurses Health Study data suggest a weak to modest reduction in breast cancer risk among coffee drinkers.
Coffee is a complex mixture of caffeine and polyphenols (remember the apples). The preparation of coffee also adds to the complexity. For instance, in Sweden, coffee is boiled and not filtered. Breast cancer is a complex mixture of diseases. One way that breast cancers may be subdivided is into those that are estrogen sensitive, so called estrogen receptor (ER) positive and those not influenced by estrogen called estrogen receptor negative. Only 25% of breast cancers are ER negative, so a reduction of these less common tumors might not show up in some reviews. Women are complex, too, and to define the relationship of coffee consumption to breast cancer many confounding dietary and lifestyle variables must be controlled.
A good example of such a study shedding light on the issue is the above mentioned study, comparing coffee consumption and breast cancer risk in Sweden. In Sweden, the coffee consumption is high with a median consumption of 3 cups per person per day. Researchers at the Karolinska Institute were able to control for confounding variables and detected a protective effect for coffee consumption and ER negative breast cancer in postmenopausal women. Women who drank more than 5 cups of coffee per day were 57% less likely to get ER negative breast cancer. They compared this data to a group of postmenopausal German women demonstrating only a more modest protection against ER negative breast cancer.
Although the mechanisms and even which compounds are active here is not yet clear, data suggests that coffee does have a protective effect on some forms of breast cancer.
