Alcohol and Cancer: What’s the Link?

A recent advisory statement from the U.S. surgeon general identified alcohol as one of the leading causes of preventable cancer, contributing to nearly 100,000 new cases of cancer and about 20,000 cancer deaths in this country per year.

Alcohol is already classified by the International Agency for Research on Cancer as a group 1 carcinogen, the highest risk group, which also includes asbestos, radiation, and tobacco. And yet, most Americans are unaware.

Farhad Islami, MD, PhD, senior scientific director of cancer disparity research at the American Cancer Society, explains the link between alcohol and cancer and answers the question: How much alcohol is safe to drink?

“We know that alcohol consumption increases the risk of seven cancer types, including cancers of the oral cavity, pharynx, larynx, esophagus, colorectal, liver, and breast,” Dr. Islami says.

Oral and throat cancers are the types most closely linked to drinking alcohol. “Data shows that about 41 percent of these cancers are attributable to alcohol consumption. And then 26 percent of laryngeal cancers (voice box), 19 percent of liver cancers, 19 percent of esophageal cancers, 16 percent of female breast cancers, and 13 percent of colorectal cancers can also be attributed to drinking.”

Lower comparative risk doesn’t mean fewer cancer cases, though, he explains. “Even though a smaller proportion of breast cancers are due to drinking than are oral cavity-pharynx cancers, at least 44,000 new cases of breast cancer every year — more than any other type of cancer — are due to alcohol consumption, simply because breast cancer is a much more common cancer.”

“Nationally, about 5 to 6 percent of all cancer cases are attributable to alcohol,” Islami says. “And while it’s often thought that only heavy drinking poses a threat, we have evidence that moderate and even light drinking can raise cancer risk. For example, moderate drinking is a known risk factor in colorectal cancer, which is on the rise among younger people in the United States. And research has shown that light drinking can raise the risk of breast cancer, which is also on the rise.”

The ethanol in alcohol causes cancer in the body in several ways, Islami says. “For example, ethanol can raise estrogen levels, which in turn increases the risk of breast cancer. In the case of most other cancers, a breakdown product of ethanol known as acetaldehyde can damage DNA and then prevent the body from repairing that damage. Alcohol can also cause inflammation and increase the absorption of carcinogens from other sources, especially tobacco smoke.”

Cancer risk goes up the more a person drinks, he says. “And because all types of alcoholic beverages contain ethanol, all pose a risk.”

"On average, men drink more alcohol than women,” Islami explains. “And because cancer risk increases with the amount of alcohol consumed, the rates and numbers of drinking-related cancers are higher in men than in women. For example, approximately 18 percent of colorectal cancer cases in men are due to alcohol, compared with about 7 percent in women. There’s also some evidence that even light drinking may raise the risk.”

Women, meanwhile, appear to be more vulnerable to harmful effects of alcohol, he says. “There’s research suggesting that women who engage in heavy or extreme binge drinking are 2 to 3 times more likely to develop cancer than men who engage in similarly risky drinking.”

The combination of drinking alcohol and smoking tobacco can raise cancer risk considerably, Islami says, to levels that are higher than from alcohol or tobacco use alone.

“This is especially true for cancers of the oral cavity, pharynx, larynx, and esophagus. And we know that people of lower socioeconomic status, as well as certain groups of people, such as Native Americans, tend to have higher rates of smoking as well as smoking and drinking combined,” he says “These groups may also have limited access to early cancer detection and treatment, which can adversely affect outlook and survival.”

All alcohol drinks contain ethanol, says Islami, which means that all alcoholic beverages pose a cancer risk, “whether wine, beer, or hard liquor. It’s often thought that wine and beer, unlike hard liquor, don’t pose a threat or may even be healthy, but that’s not the case.”

“Some older data suggested that red wine may benefit the heart and that because it contains antioxidants like resveratrol, may protect against cancer. More recent data shows that wine does not seem to be cardioprotective. And while the jury’s out on resveratrol, we recommend staying away because the harms of alcohol outweigh any possible benefits. Even light drinking raises the odds of breast cancer. For every 10 grams of pure alcohol consumed per day — about two-thirds of the amount in a standard 5-ounce glass of wine, the risk for breast cancer in the United States goes up by 7 percent in premenopausal women and by about 11 percent in postmenopausal women.”

Islami says that while men have historically consumed more alcohol than women in the United States, data shows that the drinking gender gap is closing. “Over the last several years, we’ve seen that drinking, and especially heavier drinking, is on the rise among women in the United States. Recent data shows that excessive drinking is rising among women in their late twenties and thirties, and that the prevalence of binge drinking has nearly doubled among women in their thirties and forties.”

“We’re also seeing an emerging trend of ‘high-intensity drinking,’ which is defined as drinking at levels at least 2 times as high as those of binge-drinking — that is, four drinks for women and five for men in a couple of hours. This is all very concerning.”

People often ask Islami whether it pays to stop drinking if they’ve been a drinker in the past. “The answer is yes. Cancer risk begins to decline when people stop, and over time, risk may return to the level of nondrinkers for some cancer types. On another positive note, it’s important to remember that alcohol is one of the most important preventable cancer risk factors, along with tobacco use and excess body weight.”

• Alcohol is a known carcinogen and one of the leading causes of preventable cancer.
• Regularly drinking alcohol is linked to cancers of the oral cavity, pharynx, larynx, esophagus, colon, rectum, liver, and breast.
• No amount of alcohol consumption is safe.