The more alcohol a young woman drinks before motherhood, the greater her risk of future breast cancer, a new study has warned.
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, according to a new study from Washington University School of Medicine in St Louis.
This is the first study to link increased breast cancer risk to drinking between early adolescence and first full-term pregnancy.
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," said study co-author Graham Colditz, associate director for cancer prevention and control at Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine.
"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," Colditz said.
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 of the study, Ying Liu, a School of Medicine instructor in the Division of Public Health Sciences.
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.
Researchers 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.
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.
"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. The study is published in the Journal of the National Cancer Institute.