Baku, January 9, AZERTAC

The link between drinking alcohol and developing cancer, described in a new report by the U.S. Surgeon General, may come as a surprise to many Americans, according to ScienceNews.

Although evidence for this link has been growing for some time, fewer than half of Americans are aware of the association, according to the 2019 Cancer Risk Awareness Survey. That’s in contrast to tobacco, which 89 percent of the survey respondents identified as a cancer risk.

The Surgeon General’s Advisory on Alcohol and Cancer Risk, released January 3, puts the link between drinking alcohol and developing seven different types of cancer — including esophagus, breast, liver and colorectal — in the spotlight to help increase awareness. The report calls for adding information about cancer risk to the Surgeon General’s health warning labels on alcohol. And it recommends public health professionals and health care providers discuss the risk, which generally increases the more one drinks, with patients and the public. That way, people can take the risk into account in choosing whether or how much to drink.

The World Health Organization’s International Agency for Research on Cancer first classified alcoholic beverages as carcinogenic to people in 1988. That designation is based on studies finding an association between drinking alcohol and seven types of cancer: mouth, throat, voice box, esophagus, breast, liver and colorectal.

Researchers have identified the association through observational studies, which compare groups of people in the real world, rather than a controlled setting. Generally, the observational studies compare different groups of people over time in terms of the amount they drink and their health. Such studies need to account for other factors that can contribute to cancer risk, such as smoking and age. The association persists for drinking alcohol after considering those factors and other health behaviors, says Elisa Bandera, a cancer epidemiologist at the Rutgers Cancer Institute in New Brunswick, N.J.

One of the challenges with these studies is getting accurate information about drinking patterns, including binge drinking, and lifetime consumption of alcohol, Bandera says. The studies tend to rely on self-reporting of drinking. “Because alcohol may be perceived as an unhealthy behavior by some, there is potential for underreporting the actual amount consumed, leading to potential inaccuracies in the data,” she says.

Some analyses have combined data from multiple studies to report estimates of how many cases of cancer are tied to drinking alcohol. For example, alcohol contributed to an estimated 54,000 cancer cases in women and 42,000 in men in the United States in 2019, researchers reported in CA: A Cancer Journal for Clinicians in 2024.

Worldwide, an estimated 741,000 — that’s about 4 percent — of all new cancer cases were attributable to alcohol in 2020, some of the same researchers reported in Lancet Oncology in 2021. Most of those cases were cancers of the esophagus, liver and breast. The vast majority of the total of new cancer cases were tied to drinking the equivalent of two or more drinks a day.

Another analysis that combined 572 studies and more than 486,000 cases of cancer looked at the relative risk of developing cancer. Overall, the risk increased with heavier drinking.

Developing cancer in the esophagus, for example, is about 1.3 times as likely with light drinking, which the study defined as less than one drink a day, on average, than with not drinking. That grows to nearly five times as likely with heavy drinking, defined as more than four drinks a day, compared with not drinking. Esophagus cancer is at the high end of the relative risk spectrum. For female breast cancer, the risk was slightly elevated with light drinking and about 1.6 times as likely for heavy drinking compared with not drinking, researchers reported in the British Journal of Cancer in 2014.

With the help of enzymes, alcohol gets broken down into acetaldehyde. That chemical can damage DNA, which may lead to unchecked cell growth. The process of breaking down alcohol can also lead to the formation of molecules called reactive oxygen species. These molecules can increase inflammation and harm DNA.

Some research has suggested that drinking alcohol is linked to increased levels of the hormone estrogen. It’s possible that could help explain the link between drinking and the risk of breast cancer.

Overall, there is a need for more research on how alcohol contributes to the development of cancer, says Jo Freudenheim, a cancer epidemiologist at the University at Buffalo in New York. That’s especially true for the effect of light to moderate drinking, she says.

Also, the studies on the association between drinking and cancer risk tend to discuss the risk in terms of the amount of alcohol per day on average. So an average of seven drinks per week could mean a person has one drink per day or three to four drinks on each of two days. The second pattern probably has a different biological impact than the first, Freudenheim says, “but we need more information about that.”

“Any alcohol consumption increases cancer risk to some extent. I think it’s important for people to know what their risks are,” Freudenheim says. It means they can look at the data and decide, “I am willing to take on this amount of risk.” She finds the Canadian guidelines useful: Canada’s Guidance on Alcohol and Health discusses the risk of cancer and other health harms depending on the number of drinks a person has per week.

And for smokers, the cancer risk associated with drinking alcohol is even greater, Bandera says, particularly in the mouth, throat and esophagus. The carcinogens in cigarettes dissolve in alcohol, and the ways that alcohol changes cells in the mouth and throat eases the absorption of those carcinogens. “The combined effects of alcohol and tobacco act synergistically.”