The research is preliminary, however, and has limitations. The number of heavy drinkers in the study was small, at just nine. Also, it's not possible to know which came first: brain damage from alcohol use or protection to the brain from exercise.
Still, "aerobic exercise could be a beneficial recommendation for individuals with a history of heavy alcohol use," said study author Hollis Karoly, a graduate student at the University of Colorado at Boulder. "This study represents an interesting first step in this line of research. Overall, we hope that this study inspires future research into the relationship between alcohol, exercise and the brain."
Alcohol and the brain
Scientists are intrigued by how both alcohol and exercise affect the workings of the brain. Alcohol "can remodel brain chemistry and brain structure. It can lead to neuron cell death, and alcoholism can lead to dementia," said Dr J C Garbutt, a psychiatry professor who studies alcohol use at the University of North Carolina at Chapel Hill.
"Exercise has been shown to lead to enhancement of connections in the brain and may help by lowering blood pressure and changing body metabolic factors such as high fats and high blood sugar, which can negatively affect the brain."
In the new study, the Colorado researchers studied brain scans of 37 men and 23 women, aged 21 to 55, from the Albuquerque, NM, area who answered questions about alcohol use, smoking and exercise. Thirty-nine were white.
Nine appeared to be what the study defined as problem drinkers.
Those who drank but didn't exercise had lower levels of so-called "white matter" in the brain. However, Karoly said, "we found that among high exercisers, the relationship between alcohol use and white matter damage was not significant."
White matter is important for relaying messages across the brain, Karoly said, "so damage to white matter could have a whole host of negative implications as far as cognitive processes such as memory, attention and self-regulation."
The subjects didn't take tests to assess any of those mental abilities, however.
Caution before exercise
The people in the study who appeared to exercise the most reported that they got two or more hours of exercise per week. But it's not clear what kind of exercise they got or how accurate their recollections about exercise were.
Oddly, the participants in the study who exercised the most also drank the most - nearly 1.75 drinks a day, on average. Those who exercised the least drank an average of less than 1.4 drinks a day.
Although the study showed an association between exercise and brain health, it did not prove a cause-and-effect link.
Garbutt said it's difficult to find definitive conclusions in the research. "I would view this as a very early, preliminary study that may highlight some areas for future research but doesn't provide much in the way of a solid finding to communicate to the public," he said.
Garbutt cautioned that anyone who drinks heavily or suffers from alcoholism "should get a good medical evaluation before undertaking aerobic exercise. Alcohol can affect heart rhythms, bone strength and the liver and pancreas, and one shouldn't start major exercise without knowing if there are risks such as heart problems."
But if a physician says it's OK, "exercise is good and might even help the brain," he said.
For more about alcoholism, try the US National Library of Medicine.