With the new year comes Dry January and a new surgeon general’s advisory on alcohol and cancer risk.

Moderate drinking was once thought to have benefits for the heart, but better research methods have thrown cold water on that.

“Drinking less is a great way to be healthier,” said Dr. Timothy Naimi, who directs the Canadian Institute for Substance Use Research at the University of Victoria in British Columbia.

On Friday, U.S. Surgeon General Dr. Vivek Murthy called for updating the existing surgeon general’s health warning label on alcohol-containing beverages to include the risk of cancer. His proposal would require approval from Congress.

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What’s the Harm in Drinking Alcohol?

Drinking raises the risk of several types of cancer, including colon, liver, breast and mouth and throat. Alcohol breaks down in the body into a substance called acetaldehyde, which can damage your cells and stop them from repairing themselves. That creates the conditions for cancer to grow.

Thousands of U.S. deaths per year could be prevented if people followed the government’s dietary guidelines, Naimi said.

Those guidelines advise men to limit themselves to two drinks or fewer per day and women to one drink or fewer per day. One drink is the equivalent of about one 12-ounce can of beer, a 5-ounce glass of wine or a shot of liquor.

According to Murthy’s advisory, there are about 100,000 alcohol-related cancer cases and about 20,000 alcohol-related cancer deaths annually in the United States.

“As you consider whether or how much to drink, keep in mind that less is better when it comes to cancer risk,” Murthy wrote Friday on the social media platform X.

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What About Moderate Drinking?

That idea that moderate drinking has health benefits came from imperfect studies comparing groups of people by how much they drink. Usually, that was measured at one point in time. And none of the studies randomly assigned people to drink or not drink, so they couldn’t prove cause and effect.

People who report drinking moderately tend to have higher levels of education, higher incomes and better access to health care, said Naimi.

“It turns out that when you adjust for those things, the benefits tend to disappear,” he said.

Another problem: Most studies didn’t include younger people. Almost half of the people who die from alcohol-related causes die before the age of 50.

“If you’re studying people who survived into middle age, didn’t quit drinking because of a problem and didn’t become a heavy drinker, that’s a very select group,” Naimi said. “It creates an appearance of a benefit for moderate drinkers that is actually a statistical illusion.”

Other studies challenge the idea that alcohol has benefits. These studies compare people with a gene variant that makes it unpleasant to drink to people without the gene variant. People with the variant tend to drink very little or not at all. One of these studies found people with the gene variant have a lower risk of heart disease — another blow to the idea that alcohol protects people from heart problems.

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What Do Guidelines Say?

Guidelines vary a lot from country to country but the overall trend is toward drinking less.

The United Kingdom, France, Denmark, Holland and Australia recently reviewed new evidence and lowered their alcohol consumption recommendations. Ireland will require cancer warning labels on alcohol starting in 2026.

“The scientific consensus has shifted due to the overwhelming evidence linking alcohol to over 200 health conditions, including cancers, cardiovascular diseases and injuries,” said Carina Ferreira-Borges, regional adviser for alcohol at the World Health Organization regional office for Europe.

Naimi served on an advisory committee that wanted to lower the U.S. recommendation for men to one drink per day. That advice was considered and rejected when the federal recommendations came out in 2020.

“The simple message that’s best supported by the evidence is that, if you drink, less is better when it comes to health,” Naimi said.