Resveratrol Metabolism and Bioavailability
Although trans-resveratrol appears to be well-absorbed by humans when taken orally, its bioavailability is relatively low due to its rapid metabolism and elimination. Resveratrol metabolites are primarily detected upon oral exposure to trans-resveratrol. When six healthy men and women took an oral dose of 25 mg of trans-resveratrol, only traces of the unchanged resveratrol were detected in plasma (blood). Plasma concentrations of resveratrol and metabolites peaked around 60 minutes later at concentrations around 2 micromoles/liter (491 micrograms/liter). A study in 12 healthy men administered an oral dose of 25 mg of trans-resveratrol per 70 kg of body weight reported that serum concentration of resveratrol and metabolites peaked at 30 minutes after administration. The concentration of total resveratrol (resveratrol and metabolites) ranged from 416 to 471 micrograms/liter, depending on whether resveratrol was administered in wine, vegetable juice, or grape juice. Results of another study suggested that the bioavailability of resveratrol from grape juice, which contains mostly glucosides of resveratrol (piceid), may be even lower than that of trans-resveratrol. A recent study reported that bioavailability of trans-resveratrol from red wine did not differ when the wine was consumed with a meal (low- or high-fat) versus on an empty stomach.