"Our study clearly showed that the risk of benign breast disease increased with the amount of alcohol consumed in this age group," says Graham Colditz, MD, DrPH, associate director of prevention and control at the Siteman Cancer Center at Washington University School of Medicine and Barnes-Jewish Hospital. "The study is an indication that alcohol should be limited in adolescence and early adult years and further focuses our attention on these years as key to preventing breast cancer later in life."

The study was published in the May issue of Pediatrics (online April 12, 2010).

About 80 percent of breast lumps are benign. But these benign breast lesions can be a step in a pathway leading from normal breast tissue to invasive breast cancer, so the condition is an important marker of breast cancer risk, Colditz indicates.

The researchers studied girls aged 9 to 15 years at the study's start and followed them using health surveys from 1996 to 2007. A total of 6,899 participants reported on their alcohol consumption and whether they had ever been diagnosed with benign breast disease. The participants were part of the Growing Up Today Study of more than 9,000 girls from all 50 states who are daughters of participants in the Nurses' Health Study II, one of the largest and longest-running investigations of factors that influence women's health.

The study showed that the more alcohol consumed, the more likely the participants were to have benign breast disease. Girls and young women who drank six or seven days a week were 5.5 times more likely to have benign breast disease than those who didn't drink or who had less than one drink per week. Participants who reported drinking three to five days per week had three times the risk.

The participants who were diagnosed with benign breast disease on average drank more often, drank more on each occasion and had an average daily consumption that was two times that of those who did not have benign breast disease. They also had more episodes of binge drinking.

The study is unique because it asked about alcohol intake while participants were adolescents instead of asking them to recall many years later how often they drank.

"We know from many other studies of adult women that alcohol intake later in life increases breast cancer risk," Colditz says. "But many women begin drinking alcohol as adolescents right at the time in which breast tissue is going through stages of rapid proliferation. So we wanted to see if the effect of alcohol on breast cancer risk was operative in this younger group."

The results of this study provide more evidence that steps can be taken to prevent breast cancer.

"There's growing evidence that physical activity can lower breast cancer risk," Colditz says. "We also know that diet and weight are important factors. Now it is clear that drinking habits throughout life affect breast cancer risk, as well."

Note: If no author is given, the source is cited instead.

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