A new large study shows that in the years before women’s first pregnancy, drinking even a single alcoholic beverage every day increases their risk of breast cancer in the future.
Other studies have found that alcohol consumption is associated with an increased risk of breast cancer, and found that delaying fertility increases the risk of breast cancer.
The new study is the first to study the effects of drinking alcohol between the time of menstruation and the first pregnancy. "For every 10 grams of wine per day, about 6 drinks per week, the risk increases by 11%. These risk values are estimated by comparison with those who do not drink alcohol," said Dr. Ying Liu, a lecturer in public health sciences at the University of Washington School of Medicine and author of the study. "A glass of wine is defined as a bottle or can of beer, a 4-ounce glass of wine or a small glass of spirits," Liu said.
The study shows that drinking about one glass of wine a day also increases the risk of hyperplastic benign breast disease - an increase of about 16%, a risk factor for breast cancer. The study was published in the journal in the National Cancer Institute .
researchers analyzed data from more than 91,000 women who participated in the Nurses Health Study II who had no history of cancer when they started participating in the study. They answered questions about alcohol consumption in 1989 and then followed them until 2009 to analyze their risk of breast cancer.
During the period 1991-2001, the new study also evaluated a subgroup of more than 60,000 women to investigate whether these women had benign breast disease and whether alcohol played a role during this period.
During the study period, the researchers found more than 1,600 breast cancers and 970 diagnoses of benign breast diseases.
Women drink alcohol after first menstruation and before first pregnancy are associated with the risk of two diseases, regardless of whether or not they drink alcohol after first pregnancy. This connection remains true after considering a number of other risk factors, including a history of family breast cancer.
The more alcohol a woman has, the higher the risk.
However, the researchers found only a link between pre-pregnancy drinking and breast cancer risk, but not a causal relationship.
"Breast tissues are particularly susceptible to environmental influences from the early menstruation to the first pregnancy because they are in a period of rapid cell proliferation," Liu said. However, changes in other cells during pregnancy make breast tissue less susceptible to cancer.
"Our results show that drinking alcohol before the first pregnancy can continue to increase the risk of breast cancer and benign breast diseases," Liu said. She speculated that benign breast disease may be a pathway between early alcohol consumption and breast cancer, "but not the only way."
Dr. Laura Kruper, director of the Women's Health Center and co-director of the Breast Cancer Program at City of Hope Cancer Center, said it is crucial to correctly interpret the increased risk of 11%.
Overall, the risk of breast cancer in a woman is about one in eighth, or 12% in her lifetime. "If you increase the baseline risk - 12% - by 11%, that's about 13%," Kruper said.
Liu said one in eight of the data includes drinkers and non-drinkers, but she doesn't know data on the risk of breast cancer in her lifetime.
So, although the study did find an increase in risk, Kruper said, “I think the thing to note is that the more you drink, the more you increase your risk.” Kruper and Liu believe that the study once again calls for moderate drinking. Liu said that at the age group she studied, all women “should reduce alcohol consumption to less than one drink a day, especially before the first pregnancy to reduce their risk of breast cancer.”
