For some scientists, the question will not go away. No study, these critics say, has ever proved a causal relationship between moderate drinking and lower risk of death -- only that the two often go together. It may be that moderate drinking is just something healthy people tend to do, not something that makes people healthy. "The moderate drinkers tend to do everything right -- they exercise, they don't smoke, they eat right and they drink moderately," said Kaye Middleton Fillmore, a retired sociologist from the University of California, San Francisco, who has criticized the research. "It's very hard to disentangle all of that, and that's a real problem." ... "The bottom line is there has not been a single study done on moderate alcohol consumption and mortality outcomes that is a 'gold standard' kind of study -- the kind of randomized controlled clinical trial that we would be required to have in order to approve a new pharmaceutical agent in this country," said Dr. Tim Naimi, an epidemiologist with the Centers for Disease Control and Prevention.
There are obvious issues with a randomized controlled clinical trial outlined in this article. The bigger issue seems to be that associations are overwhelming in the medical literature, and the way the media works in relation to health stories means that preliminary stuff gets way over-hyped very quickly. On the other hand, the article doesn't mention resveratrol and red wine. I suspect that's because at least there's a plausible biochemical mechanism from animal studies in this particular case in addition to an association.