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 1.5 ounces of distilled spirits, two 12-ounce beers or two 5-ounce glasses of wine. The risks to men increase significantly at 45 grams of alcohol a day, or just over three drinks.

The new report, which analysed more than 100 studies of almost five 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 recognise 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.

“When you compare this unhealthy group to those who go on drinking, it makes the current drinkers look more healthy and like they have lower mortality,” said Tim Stockwell, a scientist with the Canadian Institute for Substance Use Research who was one of the authors of the new report, which was published in JAMA Network Open last week.

Once Stockwell and his colleagues corrected for these errors and others, he said, “Lo and behold, the supposed health benefits of drinking shrink dramatically, and become non-statistically significant.”

Stockwell said that the comparisons of moderate drinkers with non-drinkers were flawed for numerous reasons. People who abstain completely from alcohol are a minority, and those who aren’t teetotalers for religious reasons are more likely to have chronic health problems, to have a disability or to be from lower-income backgrounds.

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.

“They have a lot of things going for them that protect their health, that have nothing to do with their alcohol use,” Stockwell said.

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.

New York Times News Service