Research on moderate drinking is open to all kinds of spin

Even moderate drinking could give you cancer, U.S. Surgeon General Vivek Murthy warned last week. But according to a congressionally commissioned report published last month, moderate drinking is associated with reduced overall mortality.

Although those findings are not as contradictory as they might seem, the dueling glosses reflect the complexities and ambiguities of epidemiology. The evidence on this subject is vast but open to interpretation, leaving ample room for spin, especially when it comes to this year's politically fraught revision of the federal government's dietary advice.

According to Murthy's advisory, alcohol consumption has been convincingly linked to "at least seven different types of cancer." And for some cancers, Murthy says, "evidence shows that this risk may start to increase around one or fewer drinks per day."

That level of consumption is well within the limits that the current edition of the Dietary Guidelines for Americans, produced jointly by the U.S. Department of Agriculture and the Department of Health and Human Services, recommends: two drinks per day for men, and one for women. Murthy, who thinks Congress should require cancer warning labels on alcoholic beverages, argues that even drinking within those limits could be lethal.

By Murthy's calculation, "17% of the estimated 20,000 U.S. alcohol-related cancer deaths per year occur at levels within those recommended limits." That estimate of 3,400 or so deaths represents about 0.6% of total cancer mortality in 2024.

The threat highlighted by Murthy is also modest from the perspective of individual drinkers. He says the lifetime risk of breast cancer for women who consume less than a drink per week, for example, is 11.3%, compared to 13.1% for women who consume a drink a day.

Oddly, Murthy did not see fit to mention a new evidence review by the National Academies of Sciences, Engineering and Medicine, which Congress commissioned to inform this year's revision of the dietary guidelines. The National Academies report concludes with "moderate certainty" that alcohol consumption within the currently recommended limits is associated with a 10% increase in breast cancer risk, but says "no conclusion could be drawn" regarding other cancers.

More strikingly, the National Academies' panel of experts found enough evidence to conclude with "moderate certainty" that drinkers who consume "moderate amounts of alcohol" face a lower risk of death from cardiovascular disease than teetotalers do. The panel also concluded, with the same level of confidence, that "moderate alcohol consumption is associated with lower all-cause mortality."

The meaning of such associations is scientifically controversial because they could be explained by variables other than alcohol consumption. One difficulty is that people may stop drinking because of illness or alcohol-related problems, which would tend to magnify the apparent health benefits of moderate drinking.

The National Academies report avoids that pitfall by limiting its analysis to studies where the comparison group consisted of lifetime abstainers. But as the report's authors note, moderate drinkers differ from abstainers in other ways that may affect their health, including socioeconomic status, physical activity, tobacco use and dietary habits.

Another problem is that people tend to lie about how much they drink — or, to put it more charitably, they tend to underestimate their alcohol consumption so it is more in line with what they think is socially acceptable. In light of that tendency, the data that inform official advice may be systematically biased toward finding health risks at relatively low levels of consumption, and that advice may itself increase the likelihood of underreporting.

Given the inherent limitations of observational studies that rely on self-reports of alcohol consumption and do not account for all the factors that may increase or reduce disease rates, it is not surprising that people continue to argue about the risks and benefits of moderate drinking. But one thing is clear: Most Americans like drinking, irrespective of what the latest medical study says, and they probably won't be dissuaded by new warning labels or by tweaks to official recommendations they already ignore.

Jacob Sullum is a senior editor at Reason magazine.

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