Research from Sweden’s Karolinska Institute shows a connection between significant caffeine intake—more than five cups a day—and a reduction in the risk of hormone-negative breast cancer. The study, published in Breast Cancer Research, was on 6,000 post-menopausal women, who saw a 57 percent reduced estrogen-negative breast cancer risk, no matter whether on not they used hormone-replacement therapy or alcohol, and independent of their educational status. Researchers suggest that compounds in coffee, such as trigonolline, may provide some level of protection. Hormone-receptor status was available for only 65 percent of those studied, however. And they did not specify types of coffee, so women could have been drinking decaf or different blends that are available outside of Sweden.
Some things to remember: This research was on postmenopausal women, and TNBC is more likely to affect premenopausal women, so the effects on that population are not clear. Likewise, other dietary effects may come into play here—it could be that these women had a healthier overall diet, or a healthier lifestyle otherwise, so the effects of caffeine were mediated by other factors.
Whatever the case, too much caffeine in general is not good for you. In fact, reducing caffeine can improve your overall health. Who needs the extra nervousness that coffee brings, when you are already stressed? Switching to decaf coffee can help, but while decaf has less caffeine, it is not caffeine-free. Researchers at the University of Florida compared caffeine in decaf coffee and found that different brands had from 8.6 mg to 13.9 mg, compared to an average of 85 mg for caffeinated coffee.
Source: Li, Jingmei, Seibold, Petra, Claude, Jenny C., Janys, Dieter F., Liu, Jianjun, Czene, Kamila, Humphreys, Keith Hall, Per, 'Coffee consumption modifies risk of estrogen-receptor negative breast cancer', Breast Cancer Research , vol. 13, no. 3, R49+ (2011). Find the full article at http://breast-cancer-research.com/content/pdf/bcr2879.pdf