Confused About the Health Risks of Alcohol? So Are the Scientists

Any day now, the US government will release new Guidelines on how much alcohol is safe to drink. Right now, the advice is two drinks a day for men and one for women.

By law, the Guidelines must reflect the latest evidence. The problem? The experts who write the Guidelines are working with two scientific reports that contradict each other.

One report says moderate drinking results in lower all-cause mortality.

The other says drinking even low levels of alcohol is harmful.

If the second report wins out, the fallout could be huge. If regulators adopt the ‘no safe level’ line, it could trigger a wave of litigation in the US and supercharge the lobbying of public health advocates elsewhere.

Professor Ned Calonge, head of one of the scientific committees, explained why the reports differ so much.

A quick cheat sheet on the background

Every five years, two government departments — the U.S. Department of Agriculture (USDA) and the Department of Health and Human Services (HHS) — work to reconsider the Dietary Guidelines for Americans (DGAS). The Guidelines are meant to be the gold standard for diet and alcohol advice, based on the latest science.

Normally, the evidence would be considered by the Dietary Guidelines Advisory Committee (DGAC). But this time, two separate reports were commissioned — a decision that engulfed the process in controversy.

The first report, from the National Academies of Sciences, Medicine and Engineering (NASEM) was released in December 2024. It re-affirmed that moderate consumption of alcohol is associated with lower all-cause mortality. In other words, people who drink moderately tend to live longer than those who don’t.

The second report, from six scientists commissioned by the Interagency Coordinating Committee on the Prevention of Underage Drinking (ICCPUD), was released in January 2025 and declared, “Among the U.S. population, the risk of dying from alcohol use begins at low levels of average use.”

The NASEM report

Before undertaking a study like this, NASEM asks experts to recommend scientists for the committee. “They may develop two to three names for every area of expertise,” according to Prof. Calonge. People are then invited to join.

Prof. Calonge — Associate Dean for Public Health Practice and Professor of Epidemiology, Colorado School of Public Health, and Professor of Family Medicine, University of Colorado School of Medicine

Alcohol is a highly contentious area so, not surprisingly, the committee members were heavily scrutinised. Initially, the panel included renowned alcohol experts Drs. Ken Mukamal and Eric Rimm of Harvard; after The New York Times criticised their inclusion on the panel because of perceived conflicts of interest, both researchers were removed.

“My expertise is in methodology and moving these consensus studies forward,” he said.

As mandated by Congress, the 14-member committee tackled eight specific questions about alcohol — including its cancer risk and impact on breastfeeding — by systematically reviewing existing studies and combining the results using averaging methods.

“It’s like taking the subject results and averaging them, but then accounting for very specific things like the size of the study and what we call inclusion and exclusion criteria,” said Prof Calonge, adding that the committee followed “well-established methods for doing systematic reviews.”

The NASEM committee registered their plan with the PROSPERO database, which lets other scientists check that the reviewers did what they said they were going to do.

Prof. Calonge also asked the panellists: “If the results were different from what you expected, would you be able to agree with the report?” and required written answers.

The committee then decided what existing research to include. After speaking with the USDA, they decided to focus on papers published after 2010; the 2019 DGAS committee had already done a systematic review of work published before then.

This means NASEM didn’t evaluate any studies done in the 1980s and 1990s. This was the height of the J-curve period, when scientists were actively looking for evidence that moderate drinking had health benefits.

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How the study was done

The J-curve is a graph shaped like a tick that plots alcohol use against health outcomes. It indicates that people who drink light to moderate amounts of alcohol have better health outcomes than people who drink heavily — and better outcomes than people who don’t drink, who are known as abstainers.

The J-curve, observed for decades, is now controversial because of the work of Dr. Tim Naimi and Tim Stockwell PhD. In 2023, Stockwell and Naimi published a paper taking aim at the J-curve studies, suggesting they were biased by ‘sick quitters’.

In this view, the abstainers were already unhealthy, probably because drinking damaged their health. Therefore, the reason their health outcomes seemed worse than those of moderate drinkers is just because they were in worse shape to begin with.

This was a criticism the NASEM review took seriously, so they only used studies that compared drinkers with people who had never drunk alcohol.

They also took into account the fact that most alcohol studies rely on what people say about their drinking — a topic on which people tend to lie. After choosing their studies, NASEM sent them to an external panel to grade them.

“In the studies that we ended up including, the risk of biases were low for most of them,” said Prof Calonge.

Eight subcommittees were then formed to answer each of the questions. “We took the work of the individual subcommittees and assembled them into the findings and the conclusions that we ultimately all agreed on,” said Prof Calonge.

Then the document was reviewed by another 11 reviewers, one of whom was Stockwell.

“We started roughly in January of 2024 and the report went into review in September,” said Prof Calonge. “We made the modifications and the report came out in December.” Everyone, including the reviewers, signed it off. The report was released in December 2024 and said:

“The report concludes with moderate certainty that compared with never consuming alcohol, moderate alcohol consumption is associated with lower all-cause mortality. All-cause mortality refers to the total number of deaths in a population due to any cause.”

Almost as soon as it appeared, the report was slammed as being too biased towards the alcohol industry.

“I saw no influence of undue bias or influence on committee decisions by any committee member,” said Prof. Calonge. “I stand by the results of this report. My entire career is based on unbiased, systematic evidence review and synthesis. I reject that concept entirely.”

He added: “It's Important to say what we really said, which was ‘moderate alcohol intake is associated with a lower risk of all cause mortality’. This is not a casual statement. That’s an association.”

He emphasises that it’s a very important distinction.

"The second piece is that ‘moderate certainty’ means we can make this conclusion and future research might have a different outcome.”

What about the second report?

In early January 2025, a preliminary version of the ICCPUD report was published. The work of six scientists, it came to completely different conclusions:

“Among the U.S. population, the risk of dying from alcohol use begins at low levels of average use.”

Shortly after the ICCPUD report came out, the US Alcohol Policy Alliance convened an online seminar to encourage people to leave comments in support of it on the government’s website. Speakers criticised the NASEM report for, among other things, not surveying enough literature, using too many studies from China, Japan and Korea and not having enough alcohol specialists on the committee — ironic, given there had been two alcohol experts who were removed.

The six scientists involved in the ICCPUD report are all well-known alcohol specialists, who drew on a much wider range of evidence than was used in the NASEM report, because they weren’t limited to eight specific questions. They then did what’s known as a modelling study. These types of studies are useful in situations where people are trying to predict something (like deaths from alcohol in the future), or when the data is missing or contradictory.

In the hierarchy of science, systematic reviews like the NASEM report are typically given more weight than modelling studies, because they’re based on evidence, whereas modelling studies are only as good as the assumptions fed into them.

Regardless of the merits of each study, the fight over them has been bitter, with scientists, politicians and lobbyists accusing one another of conflicts of interest and sloppy science.

International interest in the Guidelines has been intense, because if the US government declares that there is no safe level of alcohol, it will make it easier to argue for restrictions on alcohol elsewhere.

But there is one reason to believe that all the Sturm and Drang might have been for nothing. In 2020, the DGAC recommended that the Guidelines be lowered from two drinks a day for men to just one drink a day. The then-Trump administration simply ignored the recommendations and the Guidelines stayed as they were. It’s possible that history will repeat and the recommendations won’t change.

As to the question of whether the researchers ever went out and had a beer together, Prof Calonge frowned and said, “That’s not pertinent.”

Professor Ned Colange spoke to Felicity Carter in January, shortly after both reports came out.