Heart benefits of moderate drinking may be hidden in the brain

While it’s well-known that excessive alcohol consumption harms many organs, including the liver, brain, and heart, a paradox exists. About 50 years ago, studies began to suggest that moderate drinking might be beneficial for the heart.

Moderate drinking is quantified as one to two drinks per day for a man, and one drink per day for a woman. Here, a “drink” is defined as either a shot (1.5 ounces) of spirits, a 5-ounce glass of wine, or a 12-ounce bottle of beer.

Heart and health benefits

The notion of heart benefits from moderate drinking emerges from observational research involving hundreds of thousands of participants. These studies have closely monitored individuals’ drinking patterns and health over several decades. 

Participants were classified as non-drinkers, moderate drinkers, and more-than-moderate drinkers. Over time, it was observed that moderate drinkers had lower rates of coronary artery disease, including fewer heart attacks, compared to the other groups.

“That makes sense, since other studies have found that moderate drinking causes ‘good’ cholesterol to rise and blood to clot a bit less easily – both of which could explain a lower rate of heart attacks,” explained Dr. Anthony Komaroff, an internal medicine specialist and editor-in-chief of the Harvard Health Letter.

Studies of moderate drinking

However, observational studies are not without limitations. If such a study finds that moderate drinkers have a lower incidence of heart disease, it doesn’t necessarily imply that moderate drinking is the direct cause. There could be other, unmeasured variables involved. 

For instance, moderate drinkers may engage in other unknown heart-healthy practices, or non-drinkers might possess a gene that increases their risk of heart disease and also affects their alcohol tolerance.

“Good observational studies do their best to take account of all the factors that might affect an outcome,” said Dr. Komaroff. “Unfortunately, they can’t be done perfectly, and they can’t take account of risk factors that have not yet been discovered.”

Randomized controlled trials

To definitively prove the benefits of any treatment or practice, including moderate drinking, randomized controlled trials are needed. These trials involve randomly assigning participants to different groups to isolate the effect of the treatment or practice. 

However, it is challenging to conduct trials on nutritional practices like moderate drinking due to difficulties in participant adherence and long-term monitoring.

Recent studies have cast doubt on the evidence that moderate drinking reduces the risk of heart disease. This doesn’t negate past studies, but adds complexity to the existing body of research.

As it stands, the evidence suggests that while moderate drinking may offer some heart benefits, it should not be recommended solely for achieving these potential benefits. On the contrary, excessive drinking is undeniably harmful, causing multiple health issues, including heart problems.

“We all wish science could provide definitive and permanent answers to important questions, but that is rarely the case,” said Dr. Komaroff. “The best that we can do is give you our current assessment of how we weigh the sometimes-conflicting evidence. Stay tuned!”

Recent moderate drinking research

In a separate report, researchers at Massachusetts General Hospital have made a breakthrough in understanding why light to moderate alcohol consumption might be beneficial for heart health. 

Published in the Journal of the American College of Cardiology, the study reveals a link between alcohol consumption and reduced stress signaling in the brain, which may lower the risk of heart disease.

This impact appeared to significantly account for the reductions in heart disease risk seen in light to moderate drinkers participating in the study, noted the researchers.

“We are not advocating the use of alcohol to reduce the risk of heart attacks or strokes because of other concerning effects of alcohol on health,” said study senior author and cardiologist Ahmed Tawakol.

“We wanted to understand how light to moderate drinking reduces cardiovascular disease, as demonstrated by multiple other studies. And if we could find the mechanism, the goal would be to find other approaches that could replicate or induce alcohol’s protective cardiac effects without the adverse impacts of alcohol.”

Substantial risk reduction

The research involved over 50,000 participants from the Mass General Brigham Biobank. The results showed that light to moderate drinking is linked to a substantial reduction in cardiovascular disease risk. This finding persisted even after adjusting for genetic, clinical, lifestyle, and socioeconomic factors.

A subset of 754 individuals underwent PET/CT brain imaging, primarily for cancer surveillance, to examine the effect of light/moderate alcohol consumption on stress-related neural network activity. 

The imaging revealed reduced stress signaling in the amygdala – a brain region associated with stress responses – in light to moderate drinkers compared to those who abstained or drank little. 

“When the amygdala is too alert and vigilant, the sympathetic nervous system is heightened, which drives up blood pressure and increases heart rate, and triggers the release of inflammatory cells,” explained Tawakol.

“If the stress is chronic, the result is hypertension, increased inflammation, and a substantial risk of obesity, diabetes, and cardiovascular disease.”

New interventions

The experts also discovered that while light to moderate drinking lowered the risk for cardiovascular disease, any amount of alcohol increased the risk of cancer. Furthermore, excessive drinking (more than 14 drinks a week) raised heart attack risk and decreased overall brain activity, potentially affecting cognitive health.

Given these findings, Tawakol and his team propose that future research should focus on new interventions that reduce brain stress activity without alcohol’s harmful effects. 

The team is currently exploring the impact of exercise, stress-reduction techniques like meditation, and pharmacological therapies on stress-associated neural networks, aiming to induce similar cardiovascular benefits.

The research was supported by the National Institutes of Health.

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