Alcohol consumption patterns and HbA1c, C-peptide and insulin concentrations in men.

OBJECTIVE: Observational studies support inverse associations between moderate alcohol consumption and fasting insulin concentrations, but the importance of drinking pattern on the effect of alcohol on insulin sensitivity has not been fully explored. We examined the relations of alcohol consumption patterns-including average daily consumption, frequency of consumption and drinking with meals-to fasting insulin, fasting c-peptide and hemoglobin A1c (HbA1c).
METHODS: A cross-sectional study of 462 disease-free men selected from the Health Professionals' Follow-up Study to provide information on a range of drinking patterns. Study participants were 48 to 82 years of age who provided a blood sample and detailed information on diet, life-style and alcohol consumption patterns in 1994. Among the study participants, 267 men provided a fasting blood sample and contributed to the analyses of insulin and c-peptide.
RESULTS: Biologic markers were not strongly related to average alcohol consumption. Compared to abstainers, differences in insulin concentrations-all statistically non-significant-were 0.06, 1.25, 1.02, and 0.12 micro U/mL for consumers of <1, 1-1.9, 2-2.9, 3+ drinks per day, respectively. The frequency of alcohol consumption was inversely related to fasting c-peptide and insulin concentrations after controlling for average alcohol consumption and other potential confounding variables. Compared to men who reported consuming alcohol one to three days per week, c-peptide concentrations were 0.08 ng/mL and 0.29 ng/mL lower (p-trend = 0.04) in men who reported consuming alcohol on four to five days per week and six to seven days per week, respectively. Men who consumed alcohol on most days also had lower fasting insulin levels than more irregular drinkers (p-trend = 0.05).
CONCLUSIONS: Our results suggest that frequent alcohol consumption is inversely related to fasting c-peptide and insulin concentrations.