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.
“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 Dr. 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.”
Dr. 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.