Other research has linked alcohol consumption to increased breast cancer risk, as well as finding that delayed childbearing can increase breast cancer risk. Ying Liu, M.D., Ph.D., from the Washington University School of Medicine in St. Louis, MO, and colleagues analyzed data from 116,671 female registered nurses, aged 25-44 years, on medical history, reproductive history, and lifestyle.  Drinking alcohol before first pregnancy is associated with an increased risk of benign breast disease (BBD) and breast cancer, independent of drinking after first pregnancy, according to a new study published August 28 in the Journal of the National Cancer Institute. The researchers analyzed data from more than 91,000 women who took part in the Nurses' Health Study II who had no cancer history when they began. The researchers found more than 1,600 cases of breast cancer and 970 diagnoses of benign breast disease during the study period. However, data on the relationship between drinking alcohol during the period of time between a woman's first menstrual period and first pregnancy and the risk of proliferative BBD and breast cancer had not been reported. The data indicated a dose-dependent relationship, which means the more alcohol a woman drinks during that time, the higher her risk of developing breast cancer. "Breast tissues are particularly susceptible to environmental exposures between [the onset of menstruation] and first pregnancy because they undergo rapid cellular proliferation," Liu said. The authors write, "The general consistency in the patterns of association between alcohol and risk of proliferative BBD and of breast cancer lends support to the hypothesis that alcohol intake, particularly before first pregnancy when breast tissue is likely at its most vulnerable stage, may play an important role in the etiology of breast cancer."
– Drinking a glass of wine a day may cut your heart disease risk, help you lose weight, or just make you generally healthier. But if you're a woman who hasn't had kids yet, it might also give you breast cancer, a new study suggests. The study found that women who had at least one drink a day between their first menstrual cycle and their first pregnancy were at significantly higher risk of eventually developing both benign and malignant breast cancer, HealthDay reports. "The risk increased by 11% for every 10 grams a day of intake, about six drinks per week," the study's author says. Previous research has suggested the alcohol-cancer link, and that waiting to have kids could increase your risk. But this is the first study to focus on alcohol in the pre-pregnancy period. Breast tissue is especially vulnerable to carcinogens during that window, Science Codex explains.