Drinking Alcohol During Early Adulthood Raises Women's Breast Cancer Risk, Study Finds

Teens and young adult women may really want to lay off the alcohol: A new study shows a link between drinking in young adulthood and increased risk of breast cancer.

Researchers from the Washington University School of Medicine in St. Louis found that the more alcohol a woman drinks between her first period and her first full-term pregnancy, the higher her risk of developing breast cancer.

"Parents should educate their daughters about the link between drinking and risk of breast cancer and breast disease," study researcher Ying Liu, M.D., Ph.D., an instructor in the School of Medicine at Washington University School of Medicine, said in a statement. "That's very important because this time period is very critical."

The study, which is published in the Journal of the National Cancer Institute, is based on data from 91,005 mothers who were part of the Nurses' Health Study II from 1989 to 2009. They analyzed alcohol consumption during early adulthood, and how that influenced the women's risk of later developing breast cancer.

"According to our research, the lesson is clear: If a female averages a drink per day between her first period and her first full-term pregnancy, she increases her risk of breast cancer by 13 percent," study researcher Graham Colditz, M.D., Dr.P.H., the associate director for cancer prevention and control at the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine, said in a statement.

In addition to breast cancer, researchers found that a daily drink ups the risk of proliferative benign breast disease by 15 percent -- which, while not cancer itself, does raise the risk of breast cancer.

While this was an observational study, researchers did note that breast cells rapidly proliferate during adolescence and thereafter, which may make them even more susceptible at this time to carcinogens.

The study is novel in that it evaluates alcohol's effect on breast cancer when drunk in early adulthood. The International Agency for Research on Cancer already considers alcohol to cause breast cancer in adult women, with risk rising by 7 to 10 percent for every 10 daily grams of alcohol consumed, researchers wrote in the study.