Creina Stockley puts the wine and health research "in a nutshell" as a lead up to a Wine and Health Conference.
When the National Medical Health and Research Council of Australia (NH&MRC) in 1987 proposed guidelines for the responsible consumption of alcohol of "four and two" - being up to four 10 g standard drinks per day for men, and two for women - it was based on the level of consumption that was not associated with an increased risk of fatality from physiological conditions or diseases directly related to alcohol consumption (as opposed to an alcohol-abuse related condition such as such as cirrhosis of the liver).
The physiological "damage" associated with alcohol consumption primarily results from a high concentration of alcohol circulating in the blood stream prior to its metabolism in the liver, and subsequent elimination via the kidneys from the body. This "safe" level equates to approximately four and two glasses of wine (as per gender) and was based primarily on epidemiological and physiological data related to; body water differences between men and women, and the observation that women are more susceptible to "damage".
Since 1987 there have been numerous studies which have attempted to evaluate a range of data to confirm or contradict these "safe" levels. Those studies have lead to the current conclusion that not only are these levels "safe", but confer a reduction in "damage" or harm to the cardiovascular system in particular, in that there appears to be a reduction in risk of death from cardiovascular disease: Alcohol is cardioprotective. Some studies have even suggested that the risk of death from all causes is significantly reduced.
This level of between two and four drinks per day is compared to abstinence and to excessive alcohol consumption, which from the NH&MRC guidelines, is greater than eight glasses of wine per day. Graphically, the risk vs. consumption levels form a "J-curve".
While some studies have suggested that this "safe" level could be extended to six, or even eight glasses of wine per day, the most consistent data suggests that the cardioprotective effect is superseded by damage to organs and tissues, such as the liver.
This cardioprotection has been observed for both men and women across different age groups, races, and geographic regions.
The purported cardioprotective mechanisms of alcohol per se are primarily related to increasing the concentration of high density lipoprotein (HDL or "good cholesterol") in the blood. HDL transports cholesterol from the blood vessels to the liver, where it is secreted, and therefore reduces the concentration of cholesterol in the blood. It is cholesterol which accumulates in the blood vessels to restrict and eventually block blood flow.