Researchers have discovered that the more alcohol a young woman drinks before motherhood, the greater the risk of future breast cancer.
Investigators from the Washington University School of Medicine in St. Louis say that the new study shows, for the first time, an association between drinking between early adolescence and first full-term pregnancy and the risk of breast cancer.
Previous studies have looked at breast cancer risk and alcohol consumption later in life or at the effect of adolescent drinking on noncancerous breast disease.
“More and more heavy drinking is occurring on college campuses and during adolescence, and not enough people are considering future risk. But, 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,” said co-author Graham Colditz, M.D., Dr.P.H.
The study is published online in the Journal of the National Cancer Institute.
The researchers also found that for every bottle of beer, glass of wine or shot of liquor consumed daily, a young woman increases her risk of proliferative benign breast disease by 15 percent.
Although such lesions are noncancerous, their presence increases breast cancer risk by as much as 500 percent, said first author Ying Liu, M.D., Ph.D., a Washington University School of Medicine instructor in the Division of Public Health Sciences.
“Parents should educate their daughters about the link between drinking and risk of breast cancer and breast disease,” she said. “That’s very important because this time period is very critical.”
The findings are based on a review of the health histories of 91,005 mothers enrolled in the Nurses’ Health Study II from 1989 to 2009. Colditz was key to the development and administration of that and similar studies that track disease risk in female nurses.
Colditz and Liu didn’t consider the effects of adolescent and early adulthood drinking on women who didn’t have a full-term pregnancy because not enough were represented among those studied, Liu said.
Experts say that breast tissue cells are particularly susceptible to cancer-causing substances as they undergo rapid proliferation during adolescence and later. Adding to the risk is the lengthening time frame between the average age of a girl’s first menstrual cycle and the average age of a woman’s first full-term pregnancy.
Colditz doesn’t foresee any shortening of that, which is why young women should drink less, he said – to lower average daily consumption and, therefore, risk.
Knowledge of the cumulative or summative effects of alcohol and the chance of developing breast cancer is a new focus of health education.
“Reducing drinking to less than one drink per day, especially during this time period, is a key strategy to reducing lifetime risk of breast cancer,” he said.
Colditz said the findings call for more research into what young women can do to counteract alcohol’s adverse effects if they choose to drink. Past studies that didn’t consider alcohol use suggest that eating more fiber and exercising more lowers cancer risk for everyone.