cancer

Heavy drinking is clearly bad for your health. But it’s long been questioned whether moderate drinking is also risky—and, if so, how risky, exactly.

Health researchers have consistently found links between alcohol consumption and several types of cancers (namely mouth, throat, colon, rectal, liver, and breast), as well as liver diseases, injuries, and traffic accidents. But nailing down the health risks from the lower levels of drinking has been tricky. For one, much of the data on moderate drinking is from observational studies in different countries, cultures, and populations. They cannot determine if alcohol is the direct cause of any given association, and they may be swayed by other lifestyle factors. The resulting data can be noisy and inconsistent.

Moreover, many studies rely on people to self-report whether they drink and, if so, how much, which is problematic because people may not accurately assess and/or report how much they actually drink. A related problem is that studies in the past often compared drinkers to people who said they didn’t drink. But, the trouble is, non-drinking groups are often some mix of people who are lifelong abstainers and people who used to drink but quit for some reason—maybe because of health effects. This latter group has the potential to have lingering health effects from their drinking days, which could skew any comparisons looking for health differences.

Then there’s the larger, common problem with any research focused on food or beverages: some have been sponsored or somehow swayed by industry, casting suspicion on the findings, particularly the ones indicating benefits. This has been a clear problem for alcohol research. For instance, in 2018, the National Institutes of Health shut down a $100 million trial aimed at assessing the health effects (and potential benefits) of moderate drinking after it came to light that much of the funding was solicited from the alcohol industry. There was a lot of questionable communication between NIH scientists and alcohol industry representatives.

With all of that in the background, there’s been clamorous debate about how much risk, if any, people are swallowing with their evening cocktail, gameday beer, or wine with dinner.

Currently, the US dietary guidance recommends that if adults drink, they should stick to drinking in moderation, defined as “alcohol intake to two drinks or fewer in a day for men and one drink or fewer in a day for women.” But recently, health experts in the US and abroad have started calling for lower limits, noting that more data has poured in that fortifies links to cancers and other risks. In 2023, for instance, Canada released recommendations that people limit their alcohol consumption to two drinks or fewer per week—that’s down significantly from the previously recommended limit of 10 drinks per week for women and 15 drinks per week for men.

Two reviews

Now, it’s America’s turn to decide if they’ll set the bar lower, too. This year, the US will update its dietary guidelines, which are carried out by the Department of Health and Human Services and the Department of Agriculture every five years. The federal government has requested two big scientific reviews to assess the current knowledge of the health effects of alcohol, which will both inform any potential revisions to the alcohol guidelines. Now, both studies have been released and are open for discussion.

One is from the National Academies of Sciences, Engineering, and Medicine (the National Academies), which was tasked by Congress to review the current evidence on alcohol with a focus on how moderate drinking potentially affects a specific set of health outcomes. The review compared health outcomes in moderate drinkers with those of lifelong abstainers. For the review, the National Academies set up a committee of 14 experts.

The other report is from the Interagency Coordinating Committee on the Prevention of Underage Drinking (ICCPUD), which set up a Technical Review Subcommittee on Alcohol Intake and Health. For its report, the subcommittee looked not just at moderate drinking but health outcomes of a range of alcohol consumption compared to lifelong abstainers.

Based on top-line takeaways and tone, the two reports seem to have very different findings. While the National Academies review found a mix of benefits and harms from moderate drinking (one drink per day for women, and two per day for men), the ICCPUD review suggested that even the smallest amounts of alcohol (one drink per week) increased risk of death and various diseases. However, a closer look at the data shows they have some common ground.

The National Academies review

First, for the National Academies’ review, experts found sufficient evidence to assess the effects of moderate drinking on all-cause mortality, certain cancers, and cardiovascular risks. On the other hand, the reviewers found insufficient evidence to assess moderate drinking’s impact on weight changes, neurocognition, and lactation-related risks.

For all-cause mortality, a meta-analysis of data from eight studies found that moderate drinkers had a 16 percent lower risk of all-cause mortality (death from any cause) compared with lifelong abstainers. A meta-analysis of three studies suggested the risk of all-cause mortality was 23 percent lower for females who drank moderately compared to never-drinking females. Data from four studies indicated that moderate drinking males had a 16 percent lower risk of all-cause mortality than never-drinking males. Additional analyses found that the risk of all-cause mortality was 20 percent lower for moderate drinkers less than age 60 and 18 percent lower for moderate drinkers age 60 and up.

“Based on data from the eight eligible studies from 2019 to 2023, the committee concludes that compared with never consuming alcohol, moderate alcohol consumption is associated with lower all-cause mortality,” the review states. The reviewers rated the conclusion as having “moderate certainty.”

Cancer and cardiovascular disease

For a look at cancer risks, a meta-analysis of four studies on breast cancer found that moderate drinkers had an overall 10 percent higher risk than non-drinkers. An additional analysis of seven studies found that for every 10 to 14 grams of alcohol (0.7 to one standard drink) consumed per day, there was a 5 percent higher risk of breast cancer. The data indicated that people who drank higher amounts of alcohol within the moderate range had higher risks than those who drank lower amounts in the moderate range (for instance, one drink a day versus 0.5 drinks a day).

For context, the average lifetime risk of being diagnosed with breast cancer in non-drinking females is about 11 to 12 percent. A 10 percent relative increase in risk would raise a person’s absolute risk to around 12 to 13 percent. The average lifetime risk of any female dying of breast cancer is 2.5 percent.

Overall, the reviewers concluded that “consuming a moderate amount of alcohol was associated with a higher risk of breast cancer,” and the conclusion was rated as having moderate certainty.

A meta-analysis on colorectal cancer risks found a “statistically nonsignificant higher risk” in moderate drinkers compared to non-drinkers. However, studies looking at alcohol consumption at the highest levels of moderate drinking for males (e.g., two drinks per day) suggested a higher risk compared to males who drank lower amounts of alcohol in the moderate range (one drink per day).

The review concluded that there was insufficient evidence to support a link between moderate drinking and oral cavity, pharyngeal, esophageal, and laryngeal cancers.

Finally, for cardiovascular risks, meta-analyses found moderate drinking was associated with a 22 percent lower risk of heart attacks and an 11 percent lower risk of stroke (driven by lower risk of ischemic stroke, specifically). The reviewers rated these associations as low certainty, though, after noting that there was some concern for risk of bias in the studies.

For cardiovascular disease mortality, meta-analyses of four studies found an 18 percent lower risk of death among moderate drinkers compared with non-drinkers. Broken down, there was a 23 percent lower risk in female drinkers and 18 percent lower risk in male drinkers. The lower risk of cardiovascular disease mortality was rated as moderate certainty.

The ICCPUD review

The ICCPUD subcommittee’s report offered a darker outlook on moderate drinking, concluding that “alcohol use is associated with increased mortality for seven types of cancer (colorectal, female breast, liver, oral cavity, pharynx, larynx, esophagus [squamous cell type]),” and “increased risk for these cancers begins with any alcohol use and increases with higher levels of use.”

The review modeled lifetime risks of cancer and death and relative risks for a long list of problems, including infectious diseases, non-communicable diseases, and injuries. Also, it didn’t just focus on non-drinkers versus moderate drinkers, but it assessed the relative risk of six levels of drinking: one drink a week; two drinks a week; three drinks a week; seven drinks a week (one a day); 14 drinks a week (two a day), and 21 drinks a week (three a day).

Overall, the analysis is very much a rough draft. There are some places where information is missing, and some of the figures are mislabeled and difficult to read. There are two figures labeled Figure 6, for instance and Figure 7 (which may be Figure 8), is a graph that doesn’t have a Y-axis, making it difficult to interpret. The study also doesn’t discuss the level of potential bias of individual studies in its analyses. It also doesn’t make note of statistically insignificant results, nor comment on the certainty of any of its findings.

For instance, the top-line summary states: “In the United States, males and females have a 1 in 1,000 risk of dying from alcohol use if they consume more than 7 drinks per week. This risk increases to 1 in 100 if they consume more than 9 drinks per week.” But a look at the modeling behind these estimates indicates the cutoffs of when drinkers would reach a 0.1 percent or 1 percent risk of dying from alcohol use are broad. For males, a 0.1 percent lifetime risk of an alcohol-attributed death is reached at 6.5 standard drinks, with a 95 percent confidence interval spanning less than one drink per week and 13.5 drinks per week. “This lifetime risk rose to 1 in 100 people above 8.5 drinks per week,” the text reads, but the confidence interval is again between one and 14 drinks per week. So, basically, at anywhere between about one and 14 drinks a week, a male’s lifetime risk of dying from alcohol may be either 0.1 or 1 percent, according to this modeling.

Death risks

Regarding risk of death, the study did not look at all-cause mortality, like the National Academies review. Instead, it focused on deaths from causes specifically linked to alcohol. For both males and females, modeling indicated that the total lifetime risk of any alcohol-attributed death for people who consumed one, two, three, or seven drinks per week was statistically non-significant (the confidence intervals for each calculation spanned zero). Among those who have 14 drinks per week, the total lifetime risk of death was about 4 in 100 from all causes, with unintentional injuries being the biggest contributor for males and liver diseases being the biggest contributor for females. Among those who have 21 drinks per week, the risk of death was about 7 in 100 for males and 8 in 100 for females. Unintentional injuries and liver diseases were again the biggest contributors to the risk.

Some experts have speculated that the lower risk of all-cause mortality found in the National Academies’ analysis (which has been seen in previous studies) may be due to healthy lifestyle patterns among people who drink moderately rather than the protective effects of alcohol. The line of thinking would suggest that healthy lifestyle choices, like regular exercise and a healthy diet, can negate certain risks, including the potential risks of alcohol. However, the ICCPUD emphasizes the reverse argument, noting that poor health choices would likely exacerbate the risks of alcohol. “[A]lcohol would have a greater impact on the health of people who smoke, have poor diets, engage in low physical activity, are obese, have hepatitis infection, or have a family history of specific diseases than it would other individuals.”

Relative risks

In terms of relative risk of the range of conditions, generally, the ICCPUD study found small, if any, increases in risk at the three lowest levels of drinking, with risks rising with higher levels. The study’s finding of breast cancer risk was in line with the National Academies’ review. ICCPUD found that pre-menopausal females who drink moderately (one drink per day) had a 6 percent higher risk of breast cancer than non-drinkers, while post-menopausal moderate drinkers had a 17 percent higher risk. (You can see the complete set of relative risk estimates in Table A6 beginning on page 70 of the report.)

For some cancers, moderate drinking raised the risk substantially. For instance, males who have two drinks per day see their risk of esophageal cancer more than double. But, it’s important to note that the absolute risk for many of these cancers is small to begin with. The average risk of esophageal cancer in men is 0.8 percent, according to the American Cancer Society. With the increased risk from moderate drinking, it would be below 2 percent. Still, alcohol consumption increased the risks of nearly all the cancers examined, with the higher levels of alcohol consumption having the highest risk.

As for cardiovascular risks, ICCPUD’s review found low risk in several of the categories. The risk of ischemic heart disease was lower than that of nondrinkers at all six drinking levels. The risk of ischemic stroke was lower among drinkers who had one, two, three, or seven drinks per week compared to non-drinkers. At 14 and 21 drinks per week, the risk of ischemic stroke rose by 8 percent.