Many studies have hinted that alcohol, in moderation, can do a heart good. But new research suggests that moderate drinkers are no more likely than teetotallers to have clear arteries.
Protective effect not confirmed
The scientists looked at almost 2,000 patients who underwent CT angiography – an imaging test that detects "plaques" in heart arteries. Overall, there was no association between people's drinking habits and their odds of showing clogged vessels.
The findings stand in contrast to past studies that have linked moderate drinking to a lower risk of heart disease – where plaques build up in the heart arteries and may eventually trigger a heart attack.
Researchers said an advantage of the new study is that it used objective measurements.
"No prior studies have assessed the relationship between alcohol consumption and the presence of coronary heart disease as depicted by coronary CT angiography," said lead researcher Dr Julia Karady. She's with the Heart and Vascular Centre at Semmelweis University in Budapest, Hungary.
Read: Your arteries
"We could not find any relation between the presence of coronary artery disease and alcohol consumption," Karady said. "Therefore, we cannot confirm a protective [effect] of light alcohol consumption."
At the same time, she added, there was no evidence that heavier drinking raised the risk of clogged arteries.
Alcohol carries risks
However, groups like the American Heart Association (AHA) warn against excessive drinking, because it can raise blood pressure and contribute to heart failure and other cardiovascular problems.
Dozens of studies have found that moderate drinkers have a lower heart disease risk than non-drinkers – even when other health and lifestyle factors are taken into account.
In general, "moderate" is defined as no more than one glass of alcohol a day for women, and no more than two a day for men.
Read: Health benefits of moderate drinking overrated?
But those studies do not prove that alcohol, itself, protects the heart. And the AHA stresses that people should not start drinking in the hopes of gaining any health benefit – in large part because alcohol also carries risks.
Dietary guidelines from the US federal government say the same thing.
Dr Kenneth Mukamal studies lifestyle factors, including drinking habits, and the risk of heart disease. His own research has found that moderate drinkers typically have a lower risk of heart disease than non-drinkers.
People's smoking habits
According to Mukamal, the new study is too "limited" to draw any conclusions.
For one, the study patients were all sent for CT angiography because their doctors thought they might have heart disease, said Mukamal, an associate professor of medicine at Beth Israel Deaconess Medical Centre in Boston.
"They all had a similar suspicion for heart disease," he said. "So that tends to minimise the ability of any behavioural factor to influence the amount of coronary disease."
Plus, Mukamal said, it's not clear whether the study fully accounted for people's smoking habits. That's important, he noted, because smoking and drinking go hand-in-hand for some people.
Read: Smoking inflames aorta
The new findings were based on almost 2,000 patients referred for CT angiography. Almost 40 percent said they regularly drank alcohol – typically having about seven drinks a week.
Patients were considered light-to-moderate drinkers if they had no more than 14 "units" of alcohol in a week. A unit translates to about seven ounces of beer, just over three ounces of wine, or 1.35 ounces of liquor.
Larger study planned
Overall, the study found, there was no connection between people's drinking habits and their chances of having artery-clogging plaques.
And it made no difference whether wine, beer or liquor was the alcohol of choice. None appeared protective at moderate levels, Karady said.
Karady was scheduled to present the findings at the Radiological Society of North America annual meeting in Chicago. Research presented at meetings is considered preliminary until published in a peer-reviewed journal.
The researchers are planning a larger study to help confirm the new findings.
Regardless of the true relationship between moderate drinking and heart disease, the advice from experts remains the same.
If you already drink, the AHA says, do so only in moderation.
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