How alcohol impacts breast cancer risk

According to a 2021 study published in Lancet Oncology, alcohol consumption was linked to at least 740,000 new cases of seven different cancers in 2020, accounting for 4% of total cases of these cancers. Esophagus, liver, and breast cancer contributed to the highest number of cases. Several other studies have also found an association between alcohol consumption and cancer risk, including breast cancer.

When you drink alcohol, your body breaks down ethanol into a toxic chemical called acetaldehyde that can damage DNA. This damaged DNA can then lead to cells reproducing or growing haphazardly, potentially leading to the formation of cancer cells.

Drinking alcohol has also been found to increase circulating estrogen levels, possibly by stimulating the enzyme aromatase. Increased aromatase activity can lead to high levels of estrogen, which can then contribute to estrogen-receptor positive breast cancers — the most common type of breast cancer and the one that is most associated with alcohol consumption.

Altogether, these findings show "that drinking about one glass of wine a day, or one standard drink, increases risk of breast cancer over the long term by about 10 percent," said Anne McTiernan, an internist and epidemiologist who studies cancer prevention.

The amount of alcohol you drink is likely the most influential risk factor, with greater consumption being associated with higher risk. In one recent analysis, researchers found that heavy drinkers have a 52% higher risk of breast cancer compared to nondrinkers.

Drinking at a young age, before breast cells have fully differentiated, can also increase the risk of breast cancer since breast tissue is more sensitive to damage from carcinogens during this time, said Mary Beth Terry, a professor of epidemiology and environmental sciences at Columbia University.

Binge drinking (consuming four or more drinks in one sitting for women) may also uniquely increase breast cancer risk beyond what is expected from general alcohol intake. According to recent research from Terry, the risk of binge drinking may be especially harmful in younger women, potentially contributing to growing rates of breast cancer in those under 40.

Overall, "[there] is no level of alcohol use that is completely safe in terms of breast cancer," McTiernan said.

How to decrease your risk of breast cancer from alcohol

Although women are often keenly aware of their familial breast cancer risk, "you cannot change the gene makeup that you have," said Carmen Calfa, a breast medical oncologist at Sylvester Comprehensive Cancer Center in the University of Miami Health System. However, "dropping that glass of wine or changing the cocktail to a mocktail … is something women can do. [Many] are just not aware of it."

McTiernan recommends determining how much you currently drink first before thinking about how to cut back. Although a single drink is defined as 12 ounces of beer, five ounces of wine, or 1.5 ounces of liquor, you may actually be consuming two drinks in one glass depending on how it's made. You can also reduce your alcohol consumption by drinking a glass of water between each alcoholic drink.

For Calfa, having a cocktail or a glass of wine with dinner used to be routine, but she now counts her drinks and asks herself, "Do I really want this now?" before having a drink. She also often chooses nonalcoholic options, like a zero-proof beer, to enjoy a similar taste without the alcohol.

You also don't have to stop drinking completely to see benefits. Other lifestyle changes, like being more physically active, quitting smoking, and eating a balanced diet, can also reduce your breast cancer risk.

When it comes to alcohol, "you can take as much risk as you wish to take," Calfa said, "but knowing that the risk is there will empower you to make an informed choice."