Lifestyle Factors and Breast Cancer Risk

DOCTORS OFTEN ADVISE people to improve their health through simple changes to their day-to-day behavior, such as avoiding alcohol, increasing physical activity or eating a nutritious diet. A Dec. 9 session at the 2025 San Antonio Breast Cancer Symposium broke down the science behind those recommendations by highlighting research that analyzed how alcohol consumption and obesity are connected to breast cancer risk.

The Sobering Truth About Alcohol and Breast Cancer

Examining research that established a link between alcohol consumption and breast cancer, Julie R. Palmer, a cancer epidemiologist at Boston University’s Slone Epidemiology Center, pointed to a 1977 study that was one of the first to connect cancer and alcohol use. Researchers found drinking alcohol was associated with breast cancer and six other cancer types. Then, a 1982 study found people who consumed more than four drinks per week had a nearly 2.5-times higher risk for breast cancer than those who drank little or no alcohol. Additionally, a 1987 study found women who reported drinking about one alcoholic drink daily had a higher risk for breast cancer than those who did not drink any alcohol. “There’s indeed overwhelming evidence that consuming alcohol is associated with an increased risk,” Palmer said.

A 2015 analysis found women who had 5 grams of alcohol—less than one drink—per day had an elevated risk for breast cancer. This research suggests “even very light drinking may increase the risk,” Palmer said. But, she cautioned, people tend to underestimate how much alcohol they drink, so those who reported minimal drinking may have actually consumed more alcohol.

Studies have consistently showed women who binge drink—having four or more drinks in a three-hour period—have a higher risk for breast cancer than women who do not drink, according to Palmer.

Researchers have explored whether elevated risk for breast cancer from drinking affects some women more than others. A review published Nov. 24, 2024, in Alcohol Clinical & Experimental Research found both pre- and postmenopausal women who drink have an increased risk for breast cancer, but the risk was higher among postmenopausal women.

Genetics also may play a role in who develops the disease, Palmer said. People have different variants of the alcohol dehydrogenase (ADH) gene, which encodes the enzymes that convert alcohol into acetaldehyde, a toxic chemical that damages DNA and proteins. Most people have the ADH1C variant, but one type of ADH1C quickly metabolizes alcohol into acetaldehyde, and another is slow to process the chemical. In a 2006 study of women with the ADH1C variant, researchers found women who had the fast-metabolizing gene were more likely to develop breast cancer than whose with the slow-metabolizing variant.

Can Cutting Back on Drinking Lower Breast Cancer Risk?

Those who already drink alcohol may question whether cutting back could reduce their risk. There’s limited evidence to answer that question, according to Mary Beth Terry, an epidemiologist at Columbia University Herbert Irving Comprehensive Cancer Center in New York City.

In a 2023 review Terry co-authored, researchers found hundreds of studies explored the alcohol-breast cancer link, but just 21 studies measured outcomes associated with stopping or reducing alcohol consumption. Our culture often thinks people don’t need to stop drinking unless they have alcohol use disorder, Terry said. “We need to be asking these questions about patterns of use, reduction of use, cessation of use,” she said.

Some limited evidence does, however, suggest stopping alcohol consumption may lower a person’s breast cancer risk. A 2022 study found, among people who drank more than two drinks per day, people who reduced their drinking to about one drink per day had an 8% lower cancer risk than those who continued to drink heavily. Additionally, a meta-analysis published Dec. 5, 2024, in Breast Cancer Research that Terry co-authored found reducing alcohol use was associated with a lower risk of developing hormone receptor-positive breast cancer.

Many people remain unaware that alcohol can increase cancer risk. “Most people still—even though we’ve known of these data for 50 years—are not aware of this,” Terry said. In recent years, however, guidelines, such as those from the American Cancer Society, have begun to caution people to limit or stop alcohol use. Terry encouraged doctors and patients to have meaningful conversations about alcohol’s potential dangers.

How Obesity Raises Breast Cancer Risk

Obesity is another modifiable risk factor for breast cancer, as well as 12 other cancers. Researchers are investigating how obesity impacts the body at a cellular level to promote breast cancer development and progression, according to Kristy A. Brown, a cell biologist at the University of Kansas Medical Center in Kansas City.

Cellular research shows a high amount of adipose tissue, or fat, in the breast may elevate breast cancer risk and encourage disease progression, according to Brown. When fat cells die, they cause inflammation, which is a risk factor for breast cancer. Lab studies also show fat cells release fatty acids that provide energy for cancer cells. Additionally, the body uses adipose tissue to convert hormones called androgens into estrogen, which many breast cancers depend on to grow.

Obesity can also inhibit the tumor suppression protein p53, which may contribute to breast cancer proliferation, Brown said.

Brown and colleagues investigated how obesity affects people already at increased risk for breast cancer. In a 2023 study in Science Translational Medicine, they analyzed breast tissue samples from women with BRCA1 or BRCA2 genetic mutations, which are associated with a high risk for breast and ovarian cancers. They found women with obesity had more DNA damage in their breast cells than those who were at a healthy weight.

Additionally, the study found elevated levels of insulin and estradiol, a form of estrogen, also stimulated DNA damage. “As we think about cancer prevention and treatment, we should be thinking about not only cell-targeting agents but thinking about the microenvironment and potentially the whole body,” she said.

Breast cancer survivor and patient advocate Stacey Tinianov encouraged people with breast cancer and their oncologists to discuss simple behavioral changes that can improve patients’ health. “If we can give some guidance on ways that potentially they can reduce their risk of a recurrence, reduce their risk of a metastases … that’s critically important,” she said.

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