This article concludes that moderate alcohol consumption is associated with a decreased incidence of diabetes mellitus and a decreased incidence of heart disease in persons with diabetes. The authors suggest that further studies are needed to assess the long-term effects of alcohol consumption on glycemic control and noncardiac complications in persons with diabetes.

Howard, A. A., Arnsten, J. H., Gourevitch, M. N. (2004). Effect of alcohol consumption on diabetes mellitus: a systematic review. Ann Intern Med, 140(3), 211-9.  http://www.annals.org/cgi/content/abstract/140/3/211 

Authors:  Andrea A. Howard, Julia H. Arnsten, Marc N. Gourevitch.