A new study published in the December issue of the American Journal of Clinical Nutrition (1) adds to the growing body of clinical evidence suggesting that drinking purple grape juice, made using the American Concord grape, can help heart health by slowing the oxidation of LDL (bad) cholesterol in the body.
Conducted by the Centre of Human Nutrition and the Division of Biochemistry and Human Metabolism, Dallas, the study compares the antioxidant efficacy of the flavonoids contained in purple Concord grape juice with alpha-tocopherol (Vitamin E). Vitamin E is a well known and potent antioxidant but studies comparing its antioxidant capacity with purple grape juice have never been shown in vivo.
Two groups of 15 people were chosen to either receive Vitamin E or purple Concord grape juice. Both substances prevented LDL cholesterol from oxidising with similar efficacy. Many researchers believe that oxidised LDL cholesterol contributes to atherosclerosis. However, the purple Concord grape juice was more effective than Vitamin E in this study in protecting against plasma protein oxidation.
UK expert, Dr Andrew Neil, Consultant Physician and Reader in Clinical Epidemiology, University of Oxford, comments: "This study looks very interesting; vitamin E is a potent antioxidant and the results suggest that purple Concord grape juice has a similar antioxidant capacity. It is a particularly interesting finding since epidemiological studies have shown that foods rich in flavonoids are associated with a reduced risk of cardiovacascular disease. There are, however, a restricted number of flavonoid-rich food sources and purple grape juice may represent a convenient and palatable source."
Scientists have already shown that purple grape juice has as much as three times the naturally occurring antioxidants of popular fruit juices such as orange, grapefruit and tomato (2) (3). From a nutritional perspective, a daily glass therefore counts as one serving of the 'five a day' fruits and vegetables.
Further studies have also shown that the antioxidants in purple Concord grape juice have a very similar effect to those found in red wine due to the high polyphenol content in both types of grape skins, flesh and seeds. Some studies on blood clotting and vasodilation with red wine and purple grape juice show similar results. Both purple grape juice and red wine help to reduce the stickiness of blood and increase the flexibility of arteries. These factors help to maintain the free flow of blood through the arteries (4) (5).
1. Ishwarlal Jialal et al, "Comparison of the antioxidant effects of Concord grape juice flavanoids and a-tocopherol on markers of oxidative stress in healthy adults", American Journal of Clinical Nutrition, December 2002. Co-sponsored by Welch's Foods Inc (Concord, MA) and the National Institute of Health
2. Wang H, Cao G, Prior RL. Total antioxidant capacity of fruits. Journal of Agricultural and Food Chemistry. 1996;44(3):701-705
3. McBride J. High-CRAC foods may slow ageing. USDA Agricultural Research Service Web Site, Available at http://www.ars.usda.gov/
4. Vinson JA, Teufel K, Wu N. Red wine, de-alcoholised red wine, and especially grape juice, inhibit atherosclerosis in a hamster model. Atherosclerosis. 2001;156:1:67-72
5. Freedman JE, Parker C (III), Li L, Perlman JA, Frei B, Ivanov V, Deak LR, Iafrati MD, Folts JD. Select flavonoids and whole juice from purple grapes inhibit platelet function and enhance nitric oxide release. Circulation. 2001;103:2792-2798