Purple grape juice: Far greater antioxidant protection than orange juice
provided by The University of Scranton
urple grape juice has been shown to provide far greater antioxidant effect than orange juice, according to research published in the Winter 2000/2001 issue of the Journal of Medicinal Food. In the study, which analyzed lab tests as well as results of human subjects drinking the juices, purple grape juice was shown to have significant antioxidant properties, whereas orange juice showed virtually no effect, in vivo.
The take-away message from our study is that people who are looking to improve their cardiovascular function through increased antioxidant consumption might prefer a glass of purple grape juice in the morning to orange juice, says Joe A. Vinson, PhD, and Professor of Chemistry at The University of Scranton and lead author of the study. In our tests, we saw dramatically superior antioxidant performance by the grape juice in vitro and ex vivo oxidation studies, as well as when human subjects consumed the two juices.
In the human testing, sixteen healthy subjects were asked to drink two glasses daily one morning, one evening for a week of either purple grape juice or orange juice (13 ounces of purple grape juice per day; 11 ounces of orange juice per day). After the week, blood was drawn and the LDL (low density lipoproteins) oxidation lag times were measured. In lag time measurement a well-accepted method of determining antioxidant effect LDL is isolated and exposed to an oxidizing agent. The duration of time between exposure and oxidation is called lag time. This is important because the longer it takes for LDL to oxidize, the less likely it is to contribute to the atherosclerotic process. Subjects consuming purple grape juice showed an increase in lag time of 27% an indicator of antioxidant effect comparable to that previously reported for taking a vitamin E supplement. Subjects drinking the orange juice showed no change in lag time.
Dr. Vinson notes that his study's conclusions build upon and support previous research. In 1996, research at the USDA showed that total antioxidant capacity of purple grape juice was more than three times that of either orange, grapefruit, tomato or apple juice using ORAC analysis. In 2000, Keevil, et al compared purple grape juice to orange and grapefruit juice and found that only the grape juice inhibited platelet activity in humans. Relatively low platelet activity (i.e., greater inhibition) is another indicator of healthy cardiovascular function.
Vinson also notes that the methodology employed in his study for isolating lipoproteins is novel and extremely accurate. What separates our research from some of the other work in the literature, he explains, is that we use the rapid affinity column method for isolating the LDL. This, according to Vinson, eliminates the ultracentrifugation and lengthy dialysis procedures that are typically employed to isolate the lipoproteins, both of which can cause premature oxidation and, potentially, compromise the data.
People drink fruit juice for many reasons, concludes Vinson. Orange juice, for example, is an excellent source of vitamin C, folate and potassium, nutrients many people may consume in sufficient quantity in their diets otherwise. But for people looking for dietary approaches to increase consumption of natural antioxidants that may help reduce the risk of heart disease, purple grape juice appears unique in its potential ability to provide a beneficial effect to a variety of cardiovascular functions.
Partial funding for the study was provided by The University of Scranton. Juice was provided by Welch Foods, Inc.
Dr. Vinson is a National Tour Speaker for the American Chemical Society and a spokesperson on antioxidants in foods and beverages for this society. He has authored over 50 articles, edited a book, written several book chapters, and has organized numerous symposia at national and international meetings. Joe A. Vinson, PhD, Professor of Chemistry, The University of Scranton academic.scranton.edu/faculty/vinson/.