Young women who drink alcohol every day may be raising significantly their risk of breast cancer, according to US research published Wednesday.
Each alcoholic drink a woman takes daily from when her menstrual periods start until her first full-term pregnancy ups her lifetime risk of breast cancer by 13 percent, said the study in the Journal of the National Cancer Institute.
The findings were based on a survey of 91,005 mothers in a major US health study from 1989 to 2009.
The researchers also found that each additional daily drink -- whether beer, wine or hard liquor -- raised the risk of proliferative benign breast disease by 15 percent.
The presence of these noncancerous lesions also contributes to raising breast cancer risk, according to experts at the Washington University School of Medicine.
Breast tissue cells are particularly susceptible to cancer-causing changes in youth because they grow rapidly and proliferate during adolescence and beyond, researchers said.
Another factor is the lengthening time period between the first menstrual period and the first childbirth, a trend which is likely to continue.
"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," said study author Graham Colditz, associate director for cancer prevention at Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine.
Previous research has found a link between drinking alcohol in adulthood and higher breast cancer risk.
"More and more heavy drinking is occurring on college campuses and during adolescence, and not enough people are considering future risk," said Colditz.
Health authorities say about one in eight women will be diagnosed with breast cancer in their lifetime.
Risk factors include advancing age, family history of breast cancer, having dense breasts, early menstruation, late onset menopause, having a first child after age 30 or never having children, obesity and alcohol use.