A drink a day won’t necessarily keep heart problems away.

Long-term alcohol consumption — even as little as one drink a day — may enlarge your heart’s left upper chamber and increase the risk of developing atrial fibrillation, according to new research released Wednesday.

“Our study provides the first human evidence of why daily, long-term alcohol consumption may lead to the development of this very common heart rhythm disturbance,” said Gregory Marcus, M.D., senior study author and associate professor of medicine specializing in cardiac electrophysiology at the University of California at San Francisco.

“We were somewhat surprised that a relatively small amount of alcohol was associated with a larger left atrium and subsequent atrial fibrillation.”

Atrial fibrillation is a condition in which the heart beats irregularly and fails to properly pump blood — increasing the risk for stroke and blood clots. Previous research has shown associations between drinking alcohol and ventricular cardiomyopathy (heart has trouble pumping and delivering blood to the rest of the body).

Researchers analyzed data on 5,220 participants in the Framingham Heart Study, an ongoing national research project in the United States. Participants underwent electrocardiograms to measure electrical activity of the heart. Of 17,659 EKG scans taken over six years, researchers detected 1,088 incidences of atrial fibrillation.

They also found:

  • Chronic alcohol consumption was associated with higher risk for atrial fibrillation.
  • Every 10 grams per day of alcohol (one drink a day) consumed was associated with a 5 percent higher risk of developing new-onset atrial fibrillation.
  • Every additional 10 grams of alcohol a day was linked to a 0.16 millimeter larger left atrium.
  • About 24 percent, and up to 75 percent, of the relationship between regular alcohol consumption and atrial fibrillation risk could be traced back to enlargement of the left atria.

Researchers said the relationship between atrial fibrillation and alcohol consumption remained even after considering other heart health risk factors, such as high blood pressure, diabetes or smoking.

The observational findings don’t suggest that drinking alcohol directly causes heart problems. But the results challenge the popular consumer belief that alcohol benefits the heart.

“Our data suggest atrial fibrillation might be prevented by avoiding alcohol,” Marcus said. “However, just as alcohol likely has variable effects on individuals, there are almost certainly various mechanistic subtypes of atrial fibrillation. It’s not one size fits all when it comes to the effects of alcohol and heart health.”

If you drink, the American Heart Association recommends consuming alcohol in moderation. The association also cautions people to not start drinking and suggests consulting your doctor on your risks and benefits of consuming alcohol in moderation.

The study is published in the Journal of the American Heart Association.