(Reuters Health) - Having more than one alcoholic drink a day has long been linked to increased breast cancer risk in studies involving mostly white women, but new U.S. research finds similar risk increases among black women.
Compared to light drinkers who had less than four alcoholic beverages a week, African American women who consumed at least two drinks a day were 33 percent more likely to develop invasive breast cancer, the study found. With one drink a day, black women still had an elevated risk for all types of breast malignancies.
“Many breast cancer risk factors like family history cannot be changed, however, alcohol drinking can be moderated if a woman wants to decrease her risk,” said senior study author Melissa Troester, a researcher at the University of North Carolina at Chapel Hill.
“Most studies show that risk is only significantly increased if women drink more than one drink per day,” Troester added by email.
Alcohol is a well known risk factor for breast cancer, but much of the previous research establishing this connection has been done in white women, Troester and her colleagues note in the journal Cancer, Epidemiology, Biomarkers and Prevention.
It’s possible alcohol may interfere with hormone levels in a way that encourages tumor growth, and it also might cause genetic damage that makes cancer more likely, Troester said. The type of drink most responsible for cancer seems to be whatever type of alcohol women drink the most.
“Studies of alcohol and breast cancer have been conducted in many countries across the globe, and in each country, the beverage that is most widely consumed is associated with increased risk,” Troester said. “This has led researchers to conclude that it is the alcohol content rather than the specific drink that is causing the increased risk.”
For the current study, researchers examined data on drinking habits for 22,338 African American women, including 5,018 who were diagnosed with invasive breast cancer.
Overall, 45 percent of the women said they never drank and another 21 percent said they used to consume alcohol but currently did not.
Compared to light drinkers, women who said they never drank were 12 percent more likely to develop invasive tumors. The increased risk was smaller, around 4 percent, for former drinkers and for women who currently had four to six drinks a week.
For those who had 7 to 13 drinks a week, the risk increase was 7 percent compared to light drinkers.
Other risk factors for breast cancer, such as smoking, oral contraceptive use and whether women had gone through menopause didn’t appear to alter the connection between drinking and breast malignancies, the study also found.
The study isn’t a controlled experiment designed to prove whether or how alcohol causes breast cancer. Researchers also lacked data on diet and exercise, which can influence the risk of breast malignancies, and they didn’t know why some women chose to abstain from drinking.
“Women who never drink may be different than light drinkers in other risk factors, e.g. their diet,” said Dr. Mary Daly of Fox Chase Cancer Center in Philadelphia.
“Light drinkers may be more likely to adhere to a Mediterranean diet which includes moderate alcohol intake and which has been associated with better overall health and with lower breast cancer risk,” Daly, who wasn’t involved in the study, said by email.
Even so, the current study establishes that black women have an increased risk of breast cancer with alcohol use, a connection previously seen in research of white women, said Dr. Sharon Giordano of the University of Texas MD Anderson Cancer Center in Houston.
“The take-home message is that African-American women are also at increased risk of breast cancer due to alcohol use and should be encouraged to limit alcohol use,” Giordano, who wasn’t involved in the study, said by email.
SOURCE: bit.ly/2p52Gh1 Cancer, Epidemiology, Biomarkers and Prevention, online April 18, 2017.