On Nutrition

When researchers from Tulane University in New Orleans presented data at an American Heart Association conference this spring suggesting that drinking wine with dinner could reduce risk of developing Type 2 diabetes, do you think it made headlines? Of course it did. But, as is often the case, there’s more to the story.

The researchers looked at health data from 312,400 British adults — average age 56, 95% white — who describe themselves as regular drinkers. They did not have diabetes, cardiovascular disease or cancer at the time they enrolled in the study. During the 11 years of follow-up, about 8,600 of the participants developed Type 2 diabetes. Those who consumed alcohol, especially wine, with meals were 14% less likely to have developed diabetes compared with those who imbibed without eating food. But before you go grab that bottle of pinot noir as you set the table, ask yourself this: “What about compared to participants who don’t drink at all?” We don’t know that, because the researchers excluded people who had already reduced their alcohol intake for whatever reason.

To be fair, the American Diabetes Association states that, based on clinical research, moderate alcohol intake may improve blood sugar management and insulin sensitivity, and that people who drink moderately may find that their hemoglobin A1C — a measure of blood sugar over the previous three months — is lower than during times they weren’t drinking. However, it’s unclear whether these observed benefits translate into a reduced risk of developing Type 2 diabetes.

What the Tulane research does have going for it is that it looked at not just how much alcohol people drink — like most research on alcohol intake and health — but the timing of that drinking and whether participants actually went on to develop diabetes. But my second question, after “What about the nondrinkers?” is this: In what ways do people who drink with meals differ from people who drink just to drink?

The researchers did try to account for factors such as age, sex, physical activity, diet quality, smoking status, high blood pressure or high cholesterol and socioeconomic status. But what else might influence whether someone chooses to imbibe just because it’s 5 o’clock somewhere, or instead decides to limit alcohol to mealtimes? Could that unseen factor also influence other health-related decisions? The ADA recommends that people who don’t drink regularly shouldn’t start, in part because other aspects of moderate drinkers’ lives may be behind observed links between alcohol and positive health outcomes.

Another issue is that drinking habits were self-reported, an acknowledged downside of nutrition and lifestyle research among free-living humans. Never underestimate the desire — whether conscious or unconscious — to “look good” to researchers, or to look better to yourself. “Oh no … I never drink hard liquor. Only wine” or “I only drink moderately,” or “I only drink with dinner.” If you have enough people trying to save face or simply not remembering their habits accurately, that can skew results.

In keeping with recommendations from numerous health organizations, don’t start drinking if you don’t already drink. And if you do drink, keep it moderate. Moderate drinking is defined as one glass of wine or other alcoholic beverage daily for women and up to two glasses daily for men. (One glass of wine is about 5 ounces.) And, if you have diabetes, or are at increased risk of it due to family history or already elevated blood sugar levels, consider enjoying your wine or other libation only with a meal.