Study: 2 Cups of Coffee a Day for Some May Increase Breast Cancer Risk

Women who are at a higher risk of developing breast cancer and drink more than two cups of coffee a day may be increasing their estrogen levels, possibly adding to their risk for developing the disease, according to researchers at Brigham and Women's Hospital in Boston.

Higher estrogen levels can be a risk factor for women who have a family history of breast or ovarian cancer and can exacerbate endometriosis and breast pain.

In their study, published in the journal Fertility and Sterility, researchers report that women who drank the most coffee had higher levels of estradiol, a natural form of estrogen, during days 1 to 5 of their menstrual cycle, known as the follicular phase.

Researchers studied a group of 498 women, ages 36 to 45, who were not pregnant, breast-feeding or using hormones. Women were surveyed about their environment, body measurements and composition, smoking habits and diet, including sources of caffeine. The women's hormones were measured during the first five days of their menstrual cycle.

Women who drank more than one cup of coffee per day, as well as those who ingested the most cholesterol and alcohol, were found to have significantly higher estrogen levels during the follicular phase of the menstrual cycle, according to the study.

Caffeine levels from all sources were associated with higher levels of estrogen regardless of the women's age, body mass index, caloric intake, smoking and alcohol consumption. Women who ingested at least 500 mg (equivalent of 4 to 5 cups of coffee) of caffeine daily had nearly 70 percent more estrogen during the early follicular phase than women consuming less than 100 mg of caffeine each day (equivalent to less than one cup of coffee).

Other Sources: Fertility and Sterility