How Risky Is One Drink a Day?

While heavy drinking has long been linked to a greater risk of some forms of cancer, a new study has taken a look at whether light to moderate drinking poses a threat. Researchers found that, in most cases, nonsmokers who enjoyed 1 to 2 alcoholic drinks a day did not suffer a greater chance of developing cancers linked to alcohol, such as cancers of the colon, mouth, throat and liver. But there was an exception: In women, moderate consumption was linked to a higher risk of breast cancer. The study did not examine whether there were different rates of risk for different alcoholic beverages.

The team of researchers, from Harvard’s T. H. Chan School of Public Health and Boston’s Brigham and Women’s Hospital, examined data from two ongoing prospective U.S. cohort studies—the Nurses’ Health Study and the Health Professionals Follow-Up Study—which followed 88,084 women and 47,881 men over a period of at least 30 years. Participants were sent regular questionnaires asking about their health, family history, lifestyle and diet. Questions about drinking frequency were added in the late 1980s.

The authors of the new research, published in August in the BMJ (formerly the British Medical Journal), note that multiple studies have linked heavy alcohol consumption with an increased risk of some cancers, including cancer of the colorectum, mouth, throat, larynx, liver and esophagus, and have found possible links with a higher risk of cancer of the stomach, pancreas, lungs and gallbladder. Some have drawn a link between heavy alcohol consumption and an increased risk of breast cancer. But, “few prospective studies have examined the association of light to moderate alcohol consumption, the most prevalent levels of alcohol intake, with risk of total cancer,” wrote the authors.

What do they consider light to moderate drinking? The authors define it as less than 15 grams of alcohol per day for women and 30 grams of alcohol per day for men—in wine terms, that’s a little more than one glass for women and two for men.

After analyzing the data, the team found that men who consumed light to moderate amounts of alcohol and were neither smokers or former smokers suffered no discernibly higher risk of the cancers they consider alcohol-related. However, among women who consumed just 5 to 14.9 grams of alcohol a day—basically one drink—there was a correlation to a 13 percent higher risk of alcohol-related cancer, primarily due to an increase in breast cancer cases.

The authors were only examining survey data, so they cannot draw a conclusion on why the risk of breast cancer was higher. Based on past research, they theorize that breast tissue might be more susceptible to ethanol and acetaldehyde, two compounds in alcohol that are considered carcinogens.

The large studies used for the data did not ask participants to specify which types of alcohol they drank, so it is impossible to compare the risks of wine versus beer and spirits. Some research has found evidence that moderate consumption of wine can reduce the risk of some cancers, possibly due to certain compounds in wine, such as polyphenols.

The authors caution that there are no easy conclusions on this topic. One of the authors, Yin Cao, a research fellow in the nutrition department at Harvard, said women should look at other risk factors and weigh the modest increased risk of alcohol-related cancers, primarily breast cancer, against the potential benefits of alcohol in preventing heart disease. "Our study reinforces the dietary guidelines that it is important not to go beyond one drink per day for women and two drinks per day for men," Cao told one reporter.