Moderate alcohol consumption may not be good for you after all, scientists say
Most studies purporting to show moderate drinkers may live longer and be healthier are scientifically flawed, one study shows; another finds risks and benefits to having up to six drinks a week
Question: Is moderate drinking really good for you?
The straight answer: no
The facts: Many people believe a glass of wine with dinner will help them live longer and stay healthy, but the scientific evidence is shaky at best, according to a new research analysis.
Numerous studies have shown that moderate drinking is associated with a range of health benefits, including a lower heart disease risk and longer life, but investigators at the University of Victoria in Canada say many of these studies are flawed in design.
“A fundamental question is, who are these moderate drinkers being compared against?” says Tim Stockwell, the lead researcher on the analysis and director of the University of Victoria’s Centre for Addictions Research in British Columbia.
Stockwell and colleagues took a deeper look at those studies – 87 in all. A key issue is how studies have defined “abstainers”, says Stockwell. Most often, studies have compared moderate drinkers (people who have up to two drinks per day) with “current” abstainers. The problem is that this abstainer group can include people in poor health who’ve cut out alcohol.
When his team corrected for those abstainer “biases” and certain other issues, moderate drinkers no longer showed a longevity advantage. Further, only 13 of the 87 studies avoided biasing the abstainer comparison group – and these showed no health benefits.
What’s more, Stockwell says, before those corrections were made, it was actually “occasional” drinkers – people who had less than one drink per week – who lived the longest. And it’s unlikely that such infrequent drinking would be the reason for their longevity.
“Those people would be getting a biologically insignificant dose of alcohol,” says Stockwell, whose study was published in the Journal of Studies on Alcohol and Drugs.
Another study, published in the American Heart Association’s journal Circulation, reports that moderate drinking – up to six drinks a week – has both risks and benefits.
Researchers at the Harvard T.H. Chan School of Public Health in Boston analysed evidence of the risk of heart attack and stroke in the hours and days after drinking alcohol from 23 studies that included nearly 30,000 participants.
Immediately after alcohol intake, within one to three hours, just a single dose of alcohol increases heart rate and disrupts the heart’s normal pacing. But within 24 hours of drinking that dose of alcohol, there were improvements in blood flow and the function of blood vessel lining and a reduction in clotting, which is associated with a lower risk of a having heart attack or stroke from bleeds. Within a week of alcohol consumption, the risk of suffering a stroke as a result of a blood clot had fallen.
“Just after drinking, blood pressure rises and blood platelets become stickier, increasing the risk of heart attacks and strokes,” says Elizabeth Mostofsky, study lead author, instructor at the Harvard T.H. Chan School of Public Health and post-doctoral fellow at Beth Israel Deaconess Medical Centre in Boston. “However, regularly drinking small amounts of alcohol in the long term appears to both increase levels of HDL cholesterol [high density lipoprotein cholesterol], the so-called good cholesterol, and reduce the tendency to form blood clots.”
Heavy alcohol use, though, was associated with higher heart attack and stroke risks at all times studied: six to nine drinks in a day nearly doubled the risk and 19 to 30 drinks in a week elevated the risk by up to six times more.