The results of a prospective observational study by Chen WY et al. at Brigham and Women’s Hospital, Harvard Medical School, showed that even small amounts of alcohol consumption slightly increased the risk of breast cancer, and that breast cancer risk was associated with the cumulative amount of alcohol consumed in the body. Women’s risk of breast cancer increased regardless of when they started drinking alcohol as adults. The study included 105,986 women in the Nurses’ Health Study, with a total of 2.4 million years of follow-up from 1980-2008, during which 7690 patients with invasive breast cancer were diagnosed. As little as 5.0-9.9 g of alcohol per day (equivalent to 3-6 drinks per week) increased the risk of breast cancer by 15% (RR 1.15, 333 cases per 100,000 person-years). Binge drinking was associated with breast cancer risk, while frequency of drinking was not, when controlling for cumulative alcohol intake. Alcohol consumption was independently associated with breast cancer incidence whether started in early or late adulthood.