Alcohol-free red wine enhances plasma antioxidant capacity in humans.

Moderate wine consumption is reputed to exert a protective effect against coronary heart disease (CHD). The nature of the protective compounds is unclear and the mechanisms are incompletely understood. We studied whether the nonalcoholic component of wine increases plasma antioxidant capacity measured as total radical-trapping antioxidant parameter (TRAP), and whether such an effect is associated with the presence of phenolic compounds in plasma. The TRAP and plasma levels of phenolic compounds were measured in 10 healthy subjects after the ingestion of 113 mL of tap water (control) and alcohol-free red and white wine at 1-wk intervals. Both alcohol-free wines possessed an in vitro dose-dependent peroxyl-radical activity, but red wine, with a polyphenol concentration of 363 +/- 48.0 mg/L quercetin equivalent (QE), was 20 times more active (40.0 +/- 0.1 mmol/L) than white wine (1.9 +/- 0.1 mmol/L), which has a polyphenol concentration of 31 +/- 1 mg QE/L. The ingestion of alcohol-free red wine caused significant increases in plasma TRAP values and polyphenol concentrations 50 min after ingestion. Alcohol-free white wine and water had no effects on either of the plasma values. The parallel and prompt increase of antioxidant status and of circulating levels of polyphenols in fasting subjects after bolus ingestion of a moderate amount of alcohol-free red wine suggests that polyphenols are absorbed in the upper gastrointestinal tract and might be directly involved in the in vivo antioxidant defenses.