Introduction:
Moderate alcohol consumption is associated with a reduced risk of type 2 diabetes, but this relation appears stronger for women than men. The reduced risk of diabetes could be explained by improved insulin sensitivity or glycemic status, but results of intervention studies on this relation are inconsistent. Our aim was to conduct a systematic review and meta-analysis of intervention studies investigating the effect of alcohol consumption on insulin sensitivity and glycemic status.
Design:
Systematic review and meta-analysis of intervention studies.
Data sources:
PubMed and Embase were searched until May 2013 using a pre-specified search string.
Methods:
Intervention studies on the effect of more than 2 weeks alcohol consumption on biological markers of insulin sensitivity or glycemic status were identified and assessed on their quality. Pooled standardized mean differences (SMD) were calculated using either fixed or random effects models. Gender-stratified analyses and sensitivity analyses excluding studies with high doses of alcohol (> 40 g/day). In a meta-regression the influence of dosage and duration of intervention was tested.
Results:
We included 14 intervention studies in a meta-analysis on 6 glycemic endpoints. Alcohol consumption did not influence insulin sensitivity (SMD=0.06 [-0.13 to 0.26]) or fasting glucose (SMD=0.09 [-0.09 to 0.27]). Alcohol consumption reduced HbA1c (SMD=-0.62 [-1.01 to -0.23], P=0.002) and insulin concentrations (SMD=-0.17 [-0.34 to 0.00] P=0.049) compared with the control group. In women, alcohol consumption reduced fasting insulin (SMD=-0.23 [-0.41 to -0.04], P=0.019) and improved insulin sensitivity (SMD=0.19 [-0.03 to 0.41], P=0.087), but no significant differences were observed among men. Results were similar when only studies with moderate alcohol dosages were analysed and were not influenced by dosage and duration of the intervention.
Conclusions:
This study showed that moderate alcohol consumption may reduce fasting insulin and improve insulin sensitivity among women, but not among men. These effects may provide an explanation for the relation between alcohol consumption and type 2 diabetes. Furthermore, moderate alcohol consumption may reduce HbA1c levels among both men and women.
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