A systematic review showed that moderate consumption of alcoholic beverages can decrease fasting insulin and HbA1c concentrations among non-diabetic individuals and may partly explain the lower risk of type 2 diabetes among moderate drinkers observed in observational studies (**).
Moderate intake of alcoholic beverages is associated with a reduced risk of type 2 diabetes which is often explained by improved insulin sensitivity or improved glycemic status. Results of intervention studies (*) regarding this relation are inconsistent. Researchers from the Netherlands and the US conducted a systematic review and meta-analysis of intervention studies investigating the effect of alcohol consumption on insulin sensitivity and glycemic status.
The results indicated that moderate drinking of alcoholic beverages reduced fasting insulin and tended to improve insulin sensitivity among women but not among men. Similar results were observed after excluding studies with high alcohol dosages (>40 g/day). The authors pointed out that the sample sizes may have been too small and the studies of too short duration to detect influences by dosage and duration of the intervention. Thus, there can be no certainty yet whether the proposed protective mechanism can explain the observed results and more intervention studies with a longer intervention period are necessary to confirm the results.
Schrieks IC, Heil AL, Hendriks HF, Mukamal KJ, Beulens JW. The Effect of Alcohol Consumption on Insulin Sensitivity and Glycemic Status: A Systematic Review and Meta-analysis of Intervention Studies. Diabetes Care. 2015;38(4):723-732.
For more information about this article, read the scientific abstract here.
(*) Intervention studies
Intervention studies are considered to provide the most reliable evidence in epidemiological research. Intervention studies are conducted to evaluate whether an agent (i.e. moderate consumption of alcoholic beverages in the meta-analysis above) or procedure reduces the risk of developing a particular disease among individuals free from that disease at the beginning of the trial. In intervention, investigators apply treatments to individuals and then proceed to observe the effect of the treatments on the individuals.
Like intervention studies, observational studies attempt to understand cause-and-effect relationships. However, unlike interventions, the researcher is not able to control how subjects are assigned to groups and/or which treatments each group receives. Researchers record variables’ values as they naturally occur (can be retrospective or prospective) during a certain follow up period.