Most adults in the United States drink alcohol, but there is steadily growing public concern about the health effects of moderate drinking.
The latest science supports those concerns, but two recent government reports suggest potential benefits exist alongside potential risks – and some experts say that formal dietary recommendations, due to be reviewed this year, could take a more nuanced approach.
It is well-established that excessive alcohol use, including binge drinking and heavy drinking, has significant negative health effects. But recent studies have found that even low levels of drinking may be harmful, and the World Health Organization has said that “no level of alcohol consumption is safe for our health.”
The current Dietary Guidelines for Americans, from the US Department of Health and Human Services and US Department of Agriculture, say that men should limit their daily alcohol intake to two drinks or less, and one drink or less for women.
These guidelines are up for review this year, and two recent reports meant to inform that process came to seemingly competing conclusions – continuing a longstanding debate on how to weigh the potential risks and benefits of alcohol.
But public attitudes in the US are already changing.
There is a known link between alcohol and cancer, and any amount of drinking raises that risk. For Surgeon General Dr. Vivek Murthy, this “direct link” was sufficient to issue an advisory and call for an updated health warning label on alcoholic beverages to highlight it.
“Alcohol is a well-established, preventable cause of cancer responsible for about 100,000 cases of cancer and 20,000 cancer deaths annually in the United States – greater than the 13,500 alcohol-associated traffic crash fatalities per year in the US – yet the majority of Americans are unaware of this risk,” Murthy said in a statement earlier this month.
Weighing risks and benefits
One of the reports meant to inform the next edition of dietary guidelines – requested by Congress and published last month by the National Academies of Sciences, Engineering, and Medicine – reinforced the link between alcohol and cancer, but to varying degrees of certainty. The researchers, who analyzed findings from about two dozen studies, concluded with “moderate certainty” that the risk of developing breast cancer was higher among those who drank in moderation than those who didn’t drink at all. There was “low certainty” that the risk of breast cancer and colorectal cancer were higher for those who drank more in moderation than those who drank less, and no association with other throat and neck cancers.
But the same report also found some potential positive associations between moderate drinking and health. Compared with people who never consume alcohol, those who drink in moderation were at lower risk of heart attack and nonfatal stroke. And overall mortality from any cause was also found to be lower among those who drank in moderation compared with those who never drank.
“We encourage all adults who choose to drink to adhere to the Dietary Guidelines and consult with their healthcare providers. No one should drink to achieve health benefits, and some people should not drink at all,” he said, adding that the organization supports the use of this study to inform the guidelines as Congress intended and as previously done.
The other report, published last week by an independent panel convened by HHS’ Interagency Coordinating Committee on the Prevention of Underage Drinking, also found lower risk of stroke among those who had an average of one drink per day, a lower risk of diabetes among women who drink at this level, and increased risk for certain types of cancer.
But it conversely found that the risk of dying from alcohol use begins at low levels of average use and increases as levels of alcohol consumption increases.
Many experts respect the complexity of the science, but warn against viewing drinking alcohol as a categorically healthy habit.
“It’s misleading to say that the science isn’t settled,” said Dr. Katherine Keyes, a professor at the Columbia University Mailman School of Public Health whose research focuses on substance use epidemiology.
“There were differences in methodology and that’s why there are some differences in the results. But when you pull apart the studies, the underlying science is consistent,” said Keyes, who was part of the independent panel convened by HHS. “There are some conditions where we did see a benefit or an inverse relationship at very low levels, but they’re really outweighed by the conditions where you see not a benefit.”
Dr. Ned Calonge, chair of the committee that wrote the National Academies report, warns that the link his group found between lower all-cause mortality and moderate drinking should not be interpreted as a summary of the relationship between alcohol and health – quite the opposite, in fact.
“All cause mortality is, I would say, a problematic outcome, because it includes so many different outcomes, which increases the potential risk of bias associated with things called confounding factors, other factors that might be responsible for the outcome,” said Calonge, who is also an associate dean for public health practice and professor of epidemiology at the Colorado School of Public Health and professor of family medicine at the University of Colorado School of Medicine.
Research on the health effects of alcohol has some significant holes, which contributes to broader possibilities for interpreting the data.
“Moderate” drinking is not consistently defined, and grouping people into different categories – such as zero to three drinks per day – could skew averages when the outcomes may be very different for people at the low end of that category and the high end of that category.
The National Academies report addressed this in their finding about breast cancer risk, noting that higher amounts of drinking are associated with higher risk of breast cancer than lower amounts – even within levels considered to be “moderate.”
The gold standard for scientific research is a randomized controlled trial that actively monitors direct comparisons between scenarios with little external variability, but most studies on alcohol’s effects are based on observation without intervention.
When reviewing findings from observational studies, the strongest conclusions are drawn from strong associations between two factors, Calonge said. But the associations found in the National Academies report – the relative risks in the positive and negative directions – were not very strong, he said.
“We can’t prove cause with observational studies,” Calonge said. “These effects are important from a public health standpoint, but we can’t get above moderate certainty because there could be additional research that has different findings.”
Doctor’s guidance on alcohol: moderation
Despite the gaps in research, many experts say the evidence of risk is too strong to be ignored.
“Even if you were to align and agree that a line of evidence is closer to the truth for one disease state, you would then look over and recognize that if you just look at a different disease outcome, the findings might go in a completely different direction,” said Dr. Ahmed Tawakol, a cardiologist at Massachusetts General Hospital.
If a new drug was being studied to reduce heart disease and the clinical trials revealed that it also raised the risk of developing cancer, that drug would never be approved, he said.
“When you use that same frame of mind in reference to alcohol, we’d say that alcohol appears to have some mechanistic actions that are beneficial, but at the same time, it comes at a consequence of really unacceptable side effects,” he said. “It becomes clear that alcohol shouldn’t be considered something that you do for the purpose of health.”
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Some research suggests that part of the way alcohol use may reduce the risk of heart attacks is the impacts it has on the limbic system, such as limiting stress signals in the brain. But there are less risky ways to achieve that same goal, Tawakol said, such as exercise that comes with multiple benefits.
Still, Tawakol says that he doesn’t usually take a strong stance against alcohol when advising his patients.
“I worry when I see this kind of black and white approach,” he said. “If you choose to drink alcohol, make sure it’s done in moderation, and also put it in the context of other lifestyle factors so that you can further buffer the potential adverse effects.”
And many are already making their own choices. About 4 in 10 adults say that they don’t drink at all, while about 1 in 8 say that they’ve participated in Dry January – with more than half of that group saying they’re doing so this year. This idea is more popular among younger Americans, with nearly 1 in 5 adults younger than 45 participating in Dry January at some point.