Acute intake of phenolic-rich juice improves antioxidant status in healthy subjects

The aim of this study was to evaluate the short-term effect of a phenolic-rich juice made from grape and berries on the antioxidant status of a group of healthy human subjects. After a 48-hour washout period, after an antioxidant-poor diet, 12 fasting subjects (6 men and 6 women) consumed a single dose (400 mL) of the juice. Blood was drawn before (baseline) and 1, 2, 4, and 6 hours post intake. Similarly, urine was collected before, 1, 2, 4, 6, and 24 hours post intake. Urinary excretion of phenolics increased and peaked at 2 hours after the intake and persisted up to 6 hours post intake. Accordingly, a slight increase was observed in serum lipid–bound polyphenols from 2 to 6 hours, which was associated with a significant decrease in serum lipid peroxidation products from 2 to 6 hours. In contrast, the serum protein oxidation increased between 1 and 4 hours post intake, and later fell back to baseline levels at 6 hours. Our data indicate that phenolics from the juice were bioavailable and able to bind with the lipid fraction of serum, therefore reducing lipid peroxidation. These observations lend weight to the widely reported anti-atherosclerotic activity of phenolic compounds. Last but not least, the most striking result of this research is the increase in protein oxidation associated with the juice intake. We think that such an effect could be due to a sugar-mediated oxidation mechanism. However, further studies are needed to elucidate the underlying mechanism of this pro-oxidant response.