A new study has challenged widespread assumptions that a glass of wine a day is actually good for your health. Moderate alcohol consumption does not significantly decrease overall mortality, the study found, but just two to three and a half drinks per day can put you at greater risk of death from all causes.
The study by the Canadian Institute for Substance Use was a meta-analysis of 107 studies conducted between 1980 and 2021 which included 4.8 million participants. It found that women who consume 25g or more of ethanol per day and men who consume 45g or more per day were at greater risk of death from all causes. A standard drink in the U.S. contains about 14g.
Previous research has indicated that moderate drinkers enjoy a longer life expectancy than those who abstain from alcohol, but the study authors stated that these conclusions were based on flawed analysis. In particular, they noted that the previous studies failed to control for factors that predisposed the light to moderate drinkers to better health than non-drinkers, including dental hygiene, exercise, diet, weight, and income. Some of the previous research had failed to remove former drinkers who have stopped for health reasons from their analysis. Instead, those respondents were counted in the non-drinker category, where they would skew results.
The researchers analyzed the 107 studies and adjusted for those factors, among others, after which they concluded that there was no reduction in mortality among the low to moderate drinkers. Before adjustment, the research found that men who drink at least 1.3g but less than 25g of alcohol a day enjoyed a 16% reduction in risk of mortality compared to non-drinkers. After adjustment, the reduced risk for that cohort was 6%. Women who drank the same amount of alcohol had a 13% reduction in risk in the unadjusted data, while that benefit shrank to 1% after adjustment. As alcohol consumption rose, so did risk.
The study noted that when people tend to say they drank less than they did, which means that self-reported alcohol consumption is generally underreported. Also, many people who report themselves as lifetime abstainers are actually former drinkers.
The study recommended that further research should exclude former and occasional drinkers in order to get a clearer picture of the relative risk of drinking alcohol compared to never drinking alcohol.