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Consumption of polyphenol-rich tropical grape juice found to increase antioxidants in plasma and erythrocytes in healthy humans without increasing glucose or uric acid levels
A study published in the journal Nutrition Research examined the effects of acute consumption of organic and conventional juices made from fox grapes (Vitis labrusca L.) on antioxidant biomarkers in healthy people. Researchers from the Federal University of Santa Catarina in Brazil conducted the study.
Grape varieties and cultivation conditions influence the bioactive polyphenols in grapes.
The fox grape variety is cultivated in tropical regions and used to make grape juice.
In this study, the researchers hypothesized that polyphenols from tropical grape juice would improve redox homeostasis, which plays a role in fighting oxidative stress, in humans.
To test this, they assigned 24 participants to drink 400 milliliters (mL) of conventional grape juice, organic grape juice, or water. Each intervention was followed by a 14-day washout period.
The researchers took the participants’ blood samples before and one hour after consuming the drink.
They analyzed the blood samples for erythrocyte reduced glutathione, total antioxidant capacity, antioxidant enzymes in erythrocytes, glucose levels, and uric acid levels.
Reduced glutathione is the stable, active form of glutathione needed for good health.
Results showed that drinking both grape juices led to increased levels of reduced glutathione and total antioxidant capacity. The ingestion of the grape juices also increased the activity of antioxidant enzymes catalase, superoxide dismutase, and glutathione peroxidase.
Drinking both grape juices also did not increase the participants’ glucose and uric acid levels.
These results showed that grape juice polyphenols were associated with increased antioxidants, and there are no chemical differences between organic and conventional juices.
Taken together, the researchers concluded that grape juice could increase the antioxidant defenses of a person without affecting his glycemic status.