WASHINGTON — A new report from the National Academies of Sciences, Engineering, and Medicine reviews scientific evidence on the relationship between moderate alcohol consumption and health outcomes. Requested by Congress, the report is intended to inform the next edition of the Dietary Guidelines for Americans. The National Academies’ report does not offer dietary recommendations or advice.

The committee that wrote the report examined evidence on the relationship between moderate alcohol consumption and eight specific health outcomes, including cardiovascular disease, all-cause mortality, and certain types of cancer. For each of the eight health outcomes, the committee first determined whether there was sufficient evidence to support a systematic review for each health outcome, and then conducted an original systematic review for the outcomes with sufficient evidence. The report defines moderate alcohol intake as two drinks in a day for men and one drink in a day for women, as recommended in the current Dietary Guidelines for Americans, published in 2020. The report does not compare health outcomes across different types of alcohol.

“The evidence base from which to draw conclusions about alcohol and health is imperfect, and conducting the research has many challenges — such as a lack of standardization for terms like ‘non-drinker’ or ‘moderate drinker’ and the possibility that people are underreporting their own alcohol consumption,” said committee chair Ned 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. “Our report outlines what evidence is available on alcohol and health to inform the next Dietary Guidelines for Americans, and highlights research gaps that, if addressed, could strengthen the information available to us.”

Systematic Review Findings

Any studies that formed a comparison group by combining people who have never been drinkers with people who do not currently drink but have in the past were excluded from the report’s systematic reviews to avoid “abstainer bias.” Abstainer bias could lead to a comparison group being represented as less healthy overall, thereby underestimating or overestimating the health differences between the two groups that research seeks to compare and understand. The committee also excluded studies published prior to 2010, the date of the last comprehensive DGA review of this topic, and studies with too few participants, among other criteria.

The committee also indicated a level of certainty for each of its findings: high, moderate, or low certainty. None of the report’s conclusions reached a high level of certainty, which is unlikely without a randomized controlled trial to include in the systematic review. For some health outcomes, the committee determined no conclusion could be drawn.

• All-Cause Mortality — 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.

• Weight Changes — The report examines the relationship between alcohol and several different measures of weight change: weight-related outcomes, changes in weight, body mass index (BMI), the risk of overweight and obesity, and changes in waist circumference. The report says no conclusions could be drawn regarding the association between weight-related outcomes and moderate alcohol consumption compared with never consuming alcohol. It concluded with low certainty that in men, changes in BMI, risk of overweight, and risk of obesity are similar among men who consume amounts of alcohol at any level of moderate intake. The evidence for changes in BMI and the risk of overweight and obesity among women are inconsistent.

• Cancer — The report concluded with moderate certainty that consuming a moderate amount of alcohol is associated with a higher risk of female breast cancer compared to never consuming alcohol. It also concluded with low certainty that higher amounts of moderate alcohol consumption are associated with a higher risk of breast cancer compared to lower amounts of alcohol consumption. Among moderate alcohol consumers, the report concluded with low certainty that higher amounts of moderate consumption are associated with a higher risk of colorectal cancer compared with lower amounts of alcohol consumption. No conclusions could be drawn when comparing the risk of colorectal cancer for moderate alcohol consumers versus lifelong non-consumers, nor could an association be made between moderate alcohol consumption and oral cavity, pharyngeal, esophageal, or laryngeal cancers.

• Cardiovascular Disease — The report concludes that compared with never consuming alcohol, consuming moderate amounts of alcohol is associated with a lower risk of nonfatal myocardial infarction or heart attack (low certainty), a lower risk of nonfatal stroke (low certainty), and lower risk of cardiovascular mortality in both men and women (moderate certainty).

• Neurocognition — The report says no conclusion could be drawn regarding the association between moderate amounts of alcohol consumption and risk of developing Alzheimer’s disease, or about moderate versus never or occasional consumption and the risk of cognitive decline. The report also could not draw conclusions about the association between the risk of dementia for those with no alcohol consumption versus those with moderate alcohol consumption, or for those who consume higher versus lower amounts within moderate consumption.

The committee was also tasked with evaluating the association between maternal alcohol consumption during lactation and milk composition or production, as well as infant development. Not enough eligible studies published in or after 2010 were available to address these research questions, so the committee was unable to evaluate these associations using systematic review.

Research Gaps

Throughout its review of current literature, the committee identified a consistent set of research gaps that, if addressed, could strengthen the existing evidence on moderate alcohol consumption and health outcomes. Overarching limitations in alcohol and health research include abstainer bias; a lack of standard definitions of alcohol consumption levels and a lack of standardized cutoffs for exposure categories; underreporting of alcohol consumption by participants; lack of data stratified by smoking status, age, sex, and genetic ancestry to evaluate possible interactions with alcohol consumption and health outcomes; and limitations of observational studies. The report urges that all studies addressing the impacts of alcohol on human health speak to these limitations and consider including menopausal status as well as postpartum women and their infants when possible.

The study — undertaken by the Committee on the Review of Evidence on Alcohol and Health — was sponsored by the U.S Department of Agriculture’s Food and Nutrition Service. The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, engineering, and medicine. They operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln.

Contact:

Megan Lowry, Media Relations Manager
Office of News and Public Information
202-334-2138; email news@nas.edu