Methodology

For the study, researchers reviewed the available evidence published in the past five to 15 years on the effects of moderate alcohol consumption on weight, cancer risk, cardiovascular disease, neurocognition, and all-cause mortality, focusing specifically on studies whose comparison groups didn't combine people who never drink with former drinkers, in order to avoid bias.

"Research on the health effects of moderate drinking is challenging," wrote Ned Calonge, chair of NASEM, as well as associate dean for public health practice and professor of epidemiology at Colorado School of Public Health, in the introduction of the report. "Currently there are no published clinical trials for most important health outcomes, so even the substantial evidence base noted above is challenged by threats of bias inherent in observational studies, especially residual confounding."

The researchers defined moderate drinking as two drinks per day for men and one drink per day for women.

The committee then graded the quality of the evidence using a scale ranging from low to high certainty, with low certainty meaning the evidence was either not enough or too inconsistent to clearly assess health effects. All conclusions were also based on correlations, meaning the report doesn't explain whether alcohol consumption had a causal relationship to the outcomes.

Conclusions

For all-cause mortality, the report found strong evidence that heavy drinking — which was defined as more than three or four drinks a day — has significant effects on health, including increasing the risk of death.

"However, the association of moderate alcohol consumption with all-cause mortality is less clear," the report said, citing eight eligible studies. According to the researchers' meta-analysis, those who consumed moderate levels of alcohol had a 16% lower risk of all-cause mortality than those who never drank, a conclusion that was graded as being of moderate certainty.

Other meta-analyses in the report found that moderate drinking was associated with a lower risk of heart attack, stroke, and cardiovascular disease mortality than never drinking. The researchers graded the conclusions on nonfatal heart attack and stroke as low certainty and the conclusion on cardiovascular disease mortality as moderate certainty.

The researchers also conducted a systematic review of seven eligible studies on the relationship between alcohol and changes in weight, and found there was not enough evidence to draw a conclusion on moderate drinking's effect on weight-related outcomes compared to never drinking. They came to the same conclusion between degrees of moderate alcohol consumption and changes in weight or waist circumference.

For cancer, researchers reviewed 14 studies and found with moderate certainty that consuming a moderate amount of alcohol was associated with a higher risk of breast cancer compared to never drinking alcohol. In addition, among moderate drinkers, those who drank more had a higher risk than those who drank less — a conclusion the researchers graded as low certainty.

The researchers did not reach a conclusion on the associations between moderate drinking and the risk of colorectal, oral cavity, pharyngeal, esophageal, or laryngeal cancers. However, they did conclude with low certainty that moderate drinkers who drank more had a higher risk of colorectal cancer than moderate drinkers who drank less.

Research was mixed on a link between moderate drinking and the risk of neurocognitive problems like dementia, Alzheimer's disease, and cognitive decline. The researchers didn't draw any conclusions related to alcohol's effect on neurocognition.

Recommendations will be made for the 2025 Dietary Guidelines for Americans using the report as well as another report from a separate panel with HHS. The second report has yet to be released but is expected to come in January.

Surgeon General says alcoholic beverages should have warning labels

Meanwhile, Surgeon General Vivek Murthy on Friday said that alcoholic beverages should carry warning labels about the link between alcohol consumption and cancer risk, similar to the warning on packs of cigarettes.

Murthy said that alcohol directly contributes to 100,000 cancer cases and 20,000 related deaths each year.

"Many people out there assume that as long as they're drinking at the limits or below the limits of current guidelines of one a day for women and two for men, that there is no risk to their health or well-being," he said. "The data does not bear that out for cancer risk."

"[W]e've seen in the first two cases that when people were warned about these risks, they became part of our common knowledge. They sort of just shape our behavior," he said. "What I want people to know here is that, while we don't have data to give a precise level at which every person can drink and minimize their risk of cancer, the exact level that's right for each individual does depend on their own risk of cancer based on their genetics, their family history, environmental exposures."