Earlier this year, the previous U.S. Surgeon General, Vivek Murthy, issued an advisory report about the links between alcohol and cancer that received widespread media attention. Alcohol consumption, the report noted, increased the risk of seven types of cancer. That message aligned with an emerging conclusion among U.S. and international public health authorities that no amount of alcohol is safe, as the World Health Organization declared in 2023. (According to recent reports, the current administration has decided not to release another major study examining the adverse effects of alcohol.)

Edward Giovannucci, DSc, MD, a professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health, discussed the Surgeon General’s report in a commentary published in the journal Cancer Causes & Control, which gently challenged some of the most pessimistic conclusions. The Wellness Letter spoke with Dr. Giovannucci about the report, the debate over moderate drinking, and the specific factors that impact the role of alcohol on health.

The Wellness Letter: The Surgeon General’s report focused on the links between alcohol and cancer. Haven’t we known for a while that alcohol can cause cancer?

Edward Giovannucci: If you had asked me two decades ago whether alcohol was carcinogenic, I would have said yes, and so that hasn’t changed. But there have been incremental increases in our knowledge, and the details about some cancers have become more clearly established. So the evidence has gotten stronger.

WL: What specific cancers are we talking about?

EG: Alcohol has an impact on cancers of the mouth, larynx, throat, and esophagus. Those organs all have direct contact with the alcohol. Alcohol is metabolized in the liver, and some of these metabolites are toxic and can lead to liver disease, including liver cancer.

In the case of colorectal cancer, alcohol does reach the lining of the gastrointestinal tract, although through the blood rather than directly from contact during ingestion. In addition, bacteria in the colon rapidly convert the alcohol to acetaldehyde, which is a carcinogen.

The impact on breast cancer is a question of particularly high interest, and it’s a bit complicated. Estrogen is a risk cancer for breast cancer, and alcohol may increase estrogen levels. Alcohol does lead to increased breast cancer risk, but the magnitude of the risk is relatively small at moderate drinking levels.

It’s also important to remember that there is a dose-response relationship. Much of the research on increased cancer risk does not separate out moderate drinking, which has potential benefits as well as potential risks. For men, that’s up to 14 drinks a week—an average of two a day. For women, it’s up to seven drinks a week.

WL: What do we know about the possible benefits of moderate drinking?

EG: There’s controversy on this, but I think there’s enough evidence to say that moderate drinking may offer some protection against heart disease and diabetes. Moderate drinking also appears to protect against kidney cancer.

With regards to the other cancers, the Surgeon General’s report is correct that overall there is an increase even at moderate levels. But the report does not consider four modifying factors. The impact of moderate drinking is relatively neutral when these factors are taken into account. The exception is the small increased risk for breast cancer among women.

WL: What are those four modifying factors? Can you elaborate?

EG: The most significant is tobacco use. It turns out that the effect of alcohol is much worse in smokers than it is in nonsmokers, and that’s not surprising. Among nonsmokers, in fact, moderate drinking does not seem to lead to a statistical increase in cancer—with the major exception of breast cancer in women.

Smokers have a higher baseline rate of cancer, so any multiplying effect of alcohol on those rates is going to lead to a much higher number of cancer cases among smokers than among nonsmokers. Also, the carcinogenic effects of alcohol are amplified in smokers. For example, in smokers compared to nonsmokers, the same amount of alcohol will produce much higher levels of acetaldehyde, a carcinogen.

A second factor is the pattern of drinking. Most studies report how much participants drink on average—say, seven drinks a week if they’re in the moderate category. But one person might drink one drink a day for seven days, and another might binge and have seven drinks in one day. Drinking seven drinks in a day will have more harmful effects and reduce the possibility of any beneficial effects.

Next is whether you’re drinking while having food, perhaps as part of a meal, or whether you’re drinking on an empty stomach. Drinking with food reduces the rate of increase of alcohol blood levels. It also dilutes any effects on the parts of the body—the mouth, larynx, throat, and esophagus—that come into direct contact with the alcohol.

WL: And the fourth factor is the type of beverage?

EG: Yes, that’s the final factor. Ethanol is the specific alcohol in alcoholic beverages and is responsible for the psychoactive effects as well as the harmful health effects. That’s the case whether it is consumed in beer, hard liquors, or wine.

But wine also has compounds called polyphenols that are found in fruits and vegetables and have anti-inflammatory and antioxidant properties. Red wine specifically is very high in some polyphenols, and there’s evidence from animal studies, in vitro studies, and some human studies that they have a positive effect. That means wine might have some extra benefits. But when recommendations are made, they generally talk about total alcohol consumption rather than breaking it down into types of alcohol.

There’s some overlap in these factors. In general, people who drink wine are more likely to be doing so with meals. People who drink beer and hard liquors are more likely to be drinking on an empty stomach.

WL: But now the message being conveyed is that no amount of alcohol is beneficial. Why the change?

EG: A few decades ago, I think some of the possible benefits of drinking were being exaggerated, especially claims about red wine—that it could help you live to 100 years, and so on. As a corrective to that, more and more research in the last decade has been interpreted to mean that there are no benefits at all, that no amount of drinking is good, that even a scintilla of alcohol is going to harm you. I think that’s an extreme corrective. It’s gone too far.

WL: So what is the take-home message?

EG: It’s really a matter of weighing the possible benefits of moderate drinking against the risks of cancer. If you’re above the recommended levels of alcohol intake or have a pattern of binge-drinking, you should think about reducing or eliminating alcohol. But if you don’t smoke and you’re in the moderate drinking range, have a healthy drinking pattern, mainly drink with meals (especially wine)—and don’t have a personal history of or elevated risk for breast cancer—I would not be too concerned: The absolute added risk from an occasional drink appears small. In such cases, it’s reasonable to enjoy an occasional alcoholic beverage as part of an overall healthy lifestyle.