By Kathleen Doheny 
 
 HealthDay Reporter 
 
 WEDNESDAY, Aug. 28 (HealthDay News) -- Drinking even one alcoholic drink a day in the years before a woman's first pregnancy can increase her risk of breast cancer later in life, according to a large new study. 
 
 Other research has linked alcohol consumption to increased breast cancer risk, as well as finding that delayed childbearing can increase breast cancer risk. 
 
 The new research is thought to be the first to focus on the effect of alcohol intake during the time frame between the start of menstruation and a first pregnancy, the researchers said. 
 
 "The risk increased by 11 percent for every 10 grams a day of intake, about six drinks per week," said study author Dr. Ying Liu, an instructor of public health sciences at Washington University School of Medicine, in St. Louis. "These risk values were estimated as compared with nondrinkers." 
 
 "One drink was defined as one bottle or can of beer, a 4-ounce glass of wine or a shot of liquor," Liu said. 
 
 Drinking about one drink a day also increased the risk for proliferative benign breast disease, a risk factor for breast cancer, by about 16 percent, according to the study, which was published Aug. 28 in the Journal of the National Cancer Institute. 
 
 The researchers analyzed data from more than 91,000 women who took part in the Nurses' Health Study II who had no cancer history when they began. They answered questions on alcohol consumption in 1989 and were followed through 2009 to analyze their risk of breast cancer. 
 
 The new study also looked at whether the women contracted benign breast disease, and whether alcohol may have played a role in that condition, in a subgroup of more than 60,000 women who were evaluated from 1991 through 2001. 
 
 The researchers found more than 1,600 cases of breast cancer and 970 diagnoses of benign breast disease during the study period. 
 
 Drinking alcohol after the first menstrual period and before the first pregnancy was linked with a risk of both, regardless of whether a woman drank after the first pregnancy. The link held after accounting for multiple other risk factors, including family history of breast cancer. 
 
 The more the women drank, the higher their risk. 
 
 The researchers, however, found only a link between pre-pregnancy drinking and breast cancer risk, not a cause-and-effect relationship. 
 
 "Breast tissues are particularly susceptible to environmental exposures between [the onset of menstruation] and first pregnancy because they undergo rapid cellular proliferation," Liu said. During pregnancy, however, other cellular changes make the breast tissue less susceptible to cancer. 
 
 "Our results suggest that alcohol intake before the first pregnancy consistently increases the risk of breast cancer and the risk of proliferative [benign breast disease]," Liu said. She speculated that the benign breast disease may be a pathway linking drinking in early life and breast cancer, ''but not the only route." 
 
 It is crucial to put the 11 percent increased risk in perspective, said Dr. Laura Kruper, co-director of the breast cancer program and director of the Cooper Finkel Women's Health Center at the City of Hope Cancer Center in Duarte, Calif. 
 
 Overall, a woman's lifetime risk of breast cancer is about one in eight, or 12 percent. "If you take the baseline risk -- 12 percent -- and increase that by 11 percent, it is about 13 percent," Kruper said. 
 
 Liu said the one-in-eight statistic includes both drinkers and nondrinkers, but she did not know of a statistic for lifetime breast cancer risk for nondrinkers. 
 
 So although the study did find an increased risk, Kruper said, "I think the real take-home point is the more you drink the more you increase risk." 
 
 The research is another call for moderation, Kruper and Liu agreed. Liu said all women in the age category she studied "should reduce their drinking to less than one drink a day, especially before first pregnancy, to reduce their breast cancer risk." 
 
 More information 
 
 To learn more about risk factors for breast cancer, visit the American Cancer Society. 
 
 Copyright © 2012 HealthDay. All rights reserved. ||||| (Washington Post Staff Photo/Andrea Bruce) 
 
 Just one glass of wine or other alcoholic drink a day significantly raises the risk of breast cancer, while vigorous exercise such as running and bicycling reduces it, according to an expansive review of research on the effects of diet, nutrition and physical activity on the disease. 
 
 The report, which was issued Tuesday, concluded that drinking the equivalent of one small glass of wine, beer or other alcohol a day — about 10 grams of alcohol — is linked to an increased cancer risk of 5 percent for pre-menopausal women and 9 percent for post-menopausal women. A standard drink has 14 grams of alcohol. 
 
 "This suggests there is no level of alcohol use that is completely safe in terms of breast cancer," said Anne McTiernan, a cancer-prevention researcher at Fred Hutchinson Cancer Research Center in Seattle and one of the report's lead authors. "If a woman is drinking, it would be better if she kept it to a lower amount." 
 
 The review, by the American Institute for Cancer Research (AICR) and the World Cancer Research Fund, evaluated research in 119 studies encompassing data on 12 million women from around the world. It is the first such review since 2010, the groups said. 
 
 For the first time, researchers concluded evidence is strong that vigorous exercise reduces breast-cancer risk. Pre-menopausal women who were the most active had a 17 percent lower risk of developing malignancies compared to the least active women, while post-menopausal women had a 10 percent decreased risk. 
 
 [For women, heavy drinking has been normalized. That's dangerous.] 
 
 The researchers noted that many things influence cancer risk and that women can't control factors such as a family history of cancer. But, McTiernan said, "having a physically active lifestyle, maintaining a healthy weight throughout life and limiting alcohol — these are all steps women can take to lower their risk." 
 
 At the same time, she said, a healthy lifestyle is not a guarantee. Rather, it's more like wearing a seat belt. Many women will do everything they can to reduce their risks of breast cancer but still get diagnosed. "That's unfortunate, but that's what happens," she said. 
 
 Researchers were not able to calculate the degree to which vigorous exercise might cut the risk of alcohol consumption. What happens, for example, if a regular drinker also runs daily? 
 
 "The mechanism suggests that it could be helpful," McTiernan said. Alcohol increases estrogen, which is linked to increased breast-cancer risk, while physical activity reduces it. "But I can't say that for someone who drinks five drinks and then runs, that the exercise is going to negate the adverse effects of the alcohol." 
 
 The report found women who are overweight or obese have a higher risk of post-menopausal disease. 
 
 "If women lose just 10 percent of their weight, it's linked to reduced blood estrogen, inflammation" and other factors associated with breast cancer, McTiernan said. 
 
 The report also found limited evidence linking dairy foods, diets high in calcium and foods containing carotenoids to a lower risk of some breast cancers. Carotenoids include such fruits and vegetables as kale, apricots and carrots. 
 
 About 252,000 women in the United States are expected to be diagnosed with breast cancer this year. AICR estimates that 1 in 3 cases could be prevented if women did not drink alcohol, were physically active and maintained a healthy weight. 
 
 Read more: 
 
 Women with advanced breast cancer are surviving longer, study says 
 
 You just learned you have breast cancer. Now what? 
 
 Waiting and watching with 'Stage 0' breast cancer put to nationwide test
– Drinking a glass of wine a day may cut your heart disease risk, help you lose weight, or just make you generally healthier. But if you're a woman who hasn't had kids yet, it might also give you breast cancer, a new study suggests. The study found that women who had at least one drink a day between their first menstrual cycle and their first pregnancy were at significantly higher risk of eventually developing both benign and malignant breast cancer, HealthDay reports. "The risk increased by 11% for every 10 grams a day of intake, about six drinks per week," the study's author says. Previous research has suggested the alcohol-cancer link, and that waiting to have kids could increase your risk. But this is the first study to focus on alcohol in the pre-pregnancy period. Breast tissue is especially vulnerable to carcinogens during that window, Science Codex explains.