A study at the Medical College of Wisconsin a number of years ago showed a couple of glasses of wine a day decrease the risk of stroke and heart attack, more than this is injurious.
Indeed & very heartening!
But overall, the medical literature on the benefits of low-level alcohol consumption is more mixed. There are other studies that show no benefit from low to moderate consumption. And the 'positive' studies (like the one quoted) typically do not correct for associated possible causal factors - such as the fact that low levels of wine drinking are typically correlated with people who only drink with a meal, or that people who are possessed of the self-control or socio-demographic profile to make make good judgements on alcohol are probably also making better life-choices around diet, exercise, exposure to stress etc.
Put bluntly, since it's a bit difficult to conduct the gold-standard of clinical analysis on alcohol (the double-blind clinical trial with both trial cohorts corrected for all other confounding factors) then we don't actually know.
