Drinking two glasses of Concord grape juice daily may be as beneficial for your heart as 400 IU of vitamin E. Concord grape juice contains high levels of flavonoids that have previously been show to have antioxidant activity in test tube studies. Now, a study conducted at the University of Texas compared the antioxidant power of Concord grape juice to that of vitamin E and found that both had similar antioxidant abilities within the body, specifically toward low density lipoprotein (LDL), familiarly known as “bad cholesterol.” Oxidation of LDL is thought to be an early step in the formation of atherosclerosis.
A group of 36 patient volunteers participated in this study. To make sure all participants were on a standardized diet, volunteers were placed on a low-flavonoid diet for two weeks and remained on that diet for the duration of the study. After two weeks, volunteers were randomized to receive either 400 IU of alpha-tocopherol (vitamin E) or 10 milliliters of Concord grape juice per kilogram of body weight daily. This amounts to approximately 24 ounces of grape juice per day for an average-sized person. Since the authors of the study had already determined that 400 IU of vitamin E was enough to decrease LDL oxidation, they used that amount to compare with the grape juice.
After two weeks on these regimens, blood samples were taken for analysis. Both supplements were well absorbed, demonstrated by significant increases in flavonoids in the blood of the grape juice group and significant increases in blood levels of vitamin E over baseline in the vitamin E group. Both groups showed significant decreases in the oxidation rate of LDL — approximately 10 percent. This suggests a protective effect for both supplements in regards to atherosclerosis, which has already been documented for vitamin E.
Grape juice had an additional antioxidant effect as well — it demonstrated significant antioxidant protection in the plasma with a 20 percent decrease in oxidation of plasma proteins (vitamin E did not have this effect). The diverse nature of flavonoids allows them to dissolve in water and oil (or lipid) environments. Vitamin E, on the other hand, is only soluble in oil environments. This may give grape juice flavonoids an advantage to provide additional antioxidant protection in water environments such as the plasma.
One drawback, though, was that patients who supplemented with grape juice also increased their triglyceride level during the two-week study. The authors suggest that this was a transient effect that would not be important in healthy individuals but may be a concern with diabetic patients or patients with already-high triglyceride levels.
Flavonoids found in grape juice include catechin, epicatechin, quercetin and anthocyanins. Some of these flavonoids are readily found in other fruits, vegetables and herbs as well. This is good news for those who don’t drink wine but want its antioxidant benefits.
Cindy L. A. Jones, Ph.D.,
O’Byrne, D. J., et al. “Comparison of the antioxidant effects of Concord grape juice flavonoids and alpha-tocopherol on markers of oxidative stress in healthy adults.” The American Journal of Clinical Nutrition 2002, 76(6): 1367–1374.