For decades, large epidemiological studies have shown that people who consume moderate amounts of alcohol – less than one drink a day for women, and one to two drinks a day for men – have lower risks of major cardiovascular events like heart attacks and strokes compared with people who abstain from alcohol completely as well as those who drink more.
Scientists have never been able to tease out exactly why this is the case, however. Alcohol seems to increase levels of HDL, the “good” cholesterol, and drinkers have lower levels of a sticky protein called fibrinogen in their blood, which may reduce the risk of dangerous clots. And in small amounts, alcohol may increase insulin sensitivity. But these don’t seem to fully explain the benefit.
Petra Meier, a professor of public health at the University of Glasgow, pointed out that the study can show only associations. It can’t prove that alcohol was the reason light drinkers seemed to have less stress in their brains.
“There are a number of explanations including that light-to-moderate drinkers are different from abstainers in relation to a number of personal characteristics. These differences explain why low-level alcohol consumption appears to be associated with beneficial health outcomes, but without alcohol consumption being the causative factor,” Meier said in a statement.
