If you are a woman who drinks more than 5 cups of coffee per day, results of a new study may be music to your ears. Swedish researchers found that women who consume this amount of coffee may significantly reduce their risk of developing anti-estrogen-resistant, estrogen-receptor (ER-negative) breast cancer.
Coffee has a positive impact on breast cancer risk
Breast cancer can be divided into subtypes based on whether a hormone (estrogen or progesterone) is causing the tumor to grow, in which case the cancer should respond well to hormone suppression treatment. Therefore, breast cancer can be hormone responsive (estrogen receptor [ER] positive), non-hormone-responsive (ER-negative), progesterone receptor (PR) positive, or PR-negative.
Approximately 75 percent of all breast cancers are ER-positive, and about 65 percent of these cases are also PR-positive. The remaining cases are ER-negative or PR-negative.
In the Swedish study, which was conducted at Karolinska Institutet, investigators evaluated the relationship between coffee consumption and the risk of breast cancer among postmenopausal women—2,818 breast cancer cases and 3,111 controls without cancer. They identified the odds ratios for cancer overall and for each of the four subtypes.
When comparing coffee intake and breast cancer risk overall, the researchers found a small decrease in risk associated with drinking more than 5 cups of coffee per day when compared with 1 or fewer cups per day. However, the reduced risk was significant when the investigators focused solely on ER-negative breast cancer: women who were heavy coffee drinkers were 57 percent less likely to develop ER-negative breast cancer than women who drank 1 cup or less per day.
Why coffee appears to have this significant impact on ER-negative breast cancer is not clear. The authors speculated that coffee may contain substances, such as trigonelline and enterolactone, that differentially impact breast cancer of different ER subtypes. One earlier study, for example, published in Cancer Epidemiology, Biomarkers and Prevention, found enterolactone to be associated with a significant decrease in ER-negative breast cancer risk.
Results of this latest study from Sweden found that more than 5 cups of coffee per day may significantly reduce a woman’s chances of developing ER-negative breast cancer. Further studies are needed to verify the impact of coffee consumption on various breast cancer subtypes.
SOURCES:
Li J et al. Breast Cancer Research 2011; 13:R49. Doi:10.1186/bcr2879
Olsen A et al. Cancer Epidemiology, Biomarkers and Prevention 2004; 13:2084-89
