The health effects of wine (and alcohol in general) are the subject of considerable ongoing study. In the USA, a boom in red wine consumption was initiated in the 1990s by '60 Minutes', and other news reports on the French paradox. The French paradox refers to the lower incidence of coronary heart disease in France than in the USA despite high levels of saturated fat in the traditional French diet. Epidemiologists suspect that this difference is attributed to the high consumption of wines by the French; however this suspicion is based on limited scientific evidence.
Population studies have observed a J curve association between wine consumption and the risk of heart disease. This means that abstainers and heavy drinkers have an elevated risk, whilst moderate drinkers have a lower risk. Population studies have also found that moderate consumption of other alcoholic beverages may be cardioprotective, though the association is considerably stronger for wine. These studies have found a protective effect from both red wine as well as white wine, though evidence from laboratory studies suggests that red wine may possess superior health benefits including prevention of cancer due to the fact red wine contains more polyphenols than white wine due to the production process.
A chemical called resveratrol is thought to be at least partly responsible for red wines' health benefits, as it has been shown to exert a range of both cardioprotective as well as chemoprotective mechanisms in animal studies. Resveratrol is produced naturally by grape skins in response to fungal infection, which includes exposure to yeast during fermentation. As white wine has minimal contact with grape skins during this process, it generally contains lower levels of resveratrol. Other beneficial compounds in wine include other polyphenols, antioxidants, and flavonoids.
Red wines from South-West France and Sardinia Italy have been found to have the highest levels of procyanidins - the compounds in grape seeds responsible for making red wine good for the heart. Wines from south-west France and Sardinia have between two and four times as much procyanidins as other red wines. Procyanidins suppress the synthesis of a peptide called endothelin-1 that constricts blood vessels.
Whilst evidence from both laboratory studies as well as epidemiology (observational studies) suggests wines' cardioprotective effect, no evidence from controlled experiments - of which long-term studies are still ongoing - currently exists to determine the specific effect of wine or other alcohol on the risk of developing heart disease or stroke. Moreover, excessive consumption of alcohol including wine can cause some diseases including cirrhosis of the liver and alcoholism.