For decades, scientific studies suggested moderate drinking was better for most people’s health than not drinking at all, and could even help them live longer.
A new analysis of more than 40 years of research has concluded that many of those studies were flawed and that the opposite is true.
The review found that the risks of dying prematurely increase significantly for women once they drink 25 grams of alcohol a day, which is less than two standard cocktails containing 45 milliliters (1.5 ounces) of distilled spirits, two 360-ml beers or two 150-ml glasses of wine. The risks to men increase significantly at 45 g of alcohol a day, or just over three drinks.
The new report, which analyzed more than 100 studies of almost 5 million adults, was not designed to develop drinking recommendations, but to correct for methodological problems that plagued many of the older observational studies. Those reports consistently found that moderate drinkers were less likely to die of all causes, including those not related to alcohol consumption.
Most of those studies were observational, meaning they could identify links or associations but they could be misleading and did not prove cause and effect. Scientists said that the older studies failed to recognize that light and moderate drinkers had myriad other healthy habits and advantages, and that the abstainers used as a comparison group often included former drinkers who had given up alcohol after developing health problems.
Moderate drinkers tend to be moderate in all ways. They tend to be wealthier, are more likely to exercise and to eat a healthy diet, and are less likely to be overweight. They even have better teeth, scientists say.
The idea that moderate drinking may be beneficial dates back to 1924, when a Johns Hopkins biologist named Raymond Pearl published a graph with a J-shaped curve, the low point in the middle representing the moderate drinkers, who had the lowest rates of mortality from all causes.
The high point in the J represented the well-known risks of heavy alcohol consumption, such as liver disease and car crashes. The hook on the left represented abstainers.
In more recent decades, wine — and particularly red wine — developed a reputation for having health benefits after news stories highlighted its high concentration of a protective antioxidant called resveratrol, which is also found in blueberries and cranberries.
But the moderate alcohol hypothesis has come under increasing criticism over the years as the alcohol industry’s role in funding research has come to light, and newer studies have found that even moderate consumption of alcohol — including red wine — may contribute to cancers of the breast, esophagus and head and neck, high blood pressure and a serious heart arrhythmia called atrial fibrillation.
In January, Canada issued new guidelines warning that no amount of alcohol consumption is healthy, and urged people to cut drinking as much as possible. The new guidance, issued by the Canadian Centre on Substance Use and Addiction, was a stark departure from its 2011 guidelines, which recommended women limit themselves to no more than 10 standard drinks a week and men to no more than 15.
Now the Canadian agency says that consuming even two standard drinks a week is associated with health risks, and seven or more weekly drinks carry a high level of risk.