Drinking pattern and type 2 diabetes risk

The adverse effects of excessive consumption of alcoholic beverages are well established. However, the relationship between light to moderate consumption (≤ 30 g/day) and the risk of type 2 diabetes (T2D) is inconsistent. The question whether moderate consumption of alcoholic beverages is associated with a lower risk of type 2 diabetes holds substantial public health implications, since diabetes is widespread and the consequent (secondary) health problems this disease can damage the heart, brain, kidney and eyes.

Because of the inconsistent scientific data, researchers from Harvard University (1) investigated how the total intake of alcoholic beverages and drinking pattern (frequency vs. quantity, beverage type, drinking with meals) were associated with T2D risk. For this analysis, data from 330.000 women and 50.000 men in 3 prospective study groups (Nurses‘ Health Study, Nurses‘ Health Study II and Health Professionals‘ Follow-up Study) with a follow-up period of 24-33 years, were used. Former drinkers were excluded and confounding factors such age, smoking, eating pattern, physical activity and socio- economic status were adjusted. For the first time, not only the drinking amount but also the drinking frequency was considered.

Based on the data from these 3 large US study groups, a significantly lower risk of T2D among light to moderate consumers of alcoholic beverages compared with non-drinkers was found, in both men and women. This lower risk of T2D was largely driven by the drinking frequency instead of the quantity consumed. The inverse association was apparent at 1-2 drinking days per week in women and 3-4 days per week in men and was strongest for ≥ 5 days per week. These associations were evident regardless of the amount consumed (within the limits of moderate consumption, up to approx. 30 g of alcohol per day). This means that the main factor influencing the risk of diabetes was regular consumption. Those who consumed alcoholic beverages 5 to 6 days per week had a 24% (men) to 27% (women) lower risk of T2D compared to those who only consumed on 1 to 2 days per week. Each additional “drinking day” was associated with a 6% to 7% reduction in risk.

Drinking with meals had inconsistent but possibly modest inverse associations with the risk of T2D.

The authors concluded that light to moderate consumption of alcoholic beverages, especially regular light drinking was associated with a lower risk of T2D among both men and women. However, they also pointed out the undisputed risks associated with consuming large amounts of alcoholic beverages and emphasized that it cannot be recommended to start drinking for preventing diabetes.

In a commentary about this study, Zhang et al (2) pointed out the complex interplay of drinking frequency, drinking quantity and the risk of developing T2D, emphasizing the need to consider both factors in evaluating the effects of alcohol consumption on metabolic health.