According to a recent study, having one drink a day halved a person's risk of dying over the next four years (http://bit.ly/Ox94v).
First study to show that moderate drinkers live longer than either teetotalers or heavy drinkers was published in 1923. Still, the only way to truly answer the question of whether moderate drinking is, in itself, beneficial would be to do a RCT.
See here why any observation may be wrong (in clinical research and otherwise): http://bit.ly/18Kp3n - Proximity does not equal causation.
Before you recommend wine for CV risk reduction, consider this: 1 in 5 men are at risk of drinking problem. Men have 15% lifetime risk for alcohol abuse, 10% risk for alcohol dependence. "Each cuts your life short by 10-15 years." Heavy drinking increases risk of depression by 40%, and 80% of people dependent on alcohol are smokers
One in five men at risk of drinking problem. Reuters, 10/2009.
Alcohol literally kills: Gary Moore had 380mg/dL in his blood, Winehouse 416mg/dL when she died surrounded by 3 empty vodka bottles. Telegraph UK, 2012.
Drinking Alcohol Daily Seems to Cut the Risk for Coronary Artery Disease the Most
Taking Up Moderate Drinking in Middle Age Decreases Cardiovascular Risk
Medical News: Exercise and Alcohol Effect on Health
A glass of wine daily may prolong life. How you can you predict which patient will have a bottle daily though?
Image source: OpenClipArt.org, public domain.