Alcohol, free radicals and antioxidants.

Antioxidants in alcoholic beverages, especially polyphenolic compounds in red wine, have been proposed as an important contributory factor to the protective effect of regular alcohol use against atherosclerotic cardiovascular disease. The postulated mechanism involves quenching of free radicals with decreased oxidative damage to low density lipoprotein (LDL) hence reducing its potential atherogenicity. There is definitive in vitro evidence that extracts of red wine, white wine, grape juice and beer can inhibit the oxidation of LDL, the degree of inhibition being directly proportional to beverage polyphenolic content and able to be abolished by prior stripping of the polyphenolics from the alcoholic beverage. These in vitro antioxidant effects have not been reliably reproduced in vivo after acute or short-term administration of alcoholic beverages. In fact, in some studies where white wine or beer have been given over 2-4 week periods, enhanced oxidizability of LDL cholesterol has been reported. Such findings are consistent with the possibility that, depending on the beverage, a predominant pro-oxidant effect of alcohol itself may outweigh any antioxidant effect of beverage polyphenolics. Increased oxidant stress and enhanced lipid peroxidation with alcohol have several biologically plausible explanations and have been reported as possible mechanisms for alcohol-related toxicity and injury in various tissues. Therefore, before the promotion of any particular benefits of ingestion of polyphenolics from alcoholic beverages (especially red wine) for prevention of atherosclerotic cardiovascular disease, the balance of redox effects in vivo will need careful further clinical and laboratory evaluation.