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Abstract & Commentary
Synopsis: Ingesting moderate amounts of purple GJ each day appeared to improve endothelial function as measured by FMD in patients with known arteriosclerotic coronary arterial disease.
Source: Chou EJ, et al. Am J Cardiol. 2001;88:553-555.
Flavonoids are known to be powerful antioxidants that improve endothelial function and inhibit platelet aggregation1-3 thereby presumably slowing or preventing coronary atherosclerosis and decreasing the frequency of acute coronary syndromes. For more than 20 years, cardiologists and epidemiologists have suggested that the "French paradox" (ie, the fact that the coronary heart disease mortality rate in France is lower than it is in other industrialized nations with similar prevalences of coronary risk factors) is due to the ingestion of the flavonoids4,5 found in red wine and purple grape juice (GJ).
Dr. Eric Chou and his associates from the University of Wisconsin Medical School used an unrestricted grant from Welch’s Foods, Inc. to perform a study on the effect of 2 different doses of purple GJ alone and in combination with vitamin E on endothelial function. One group of 11 subjects consumed 21 ounces of concord GJ daily for 56 days and a second consumed approximately 10½ ounces daily for the same period of time. After 28 days all subjects were given 400 international units of vitamin E daily. Endothelial function was assessed by measuring flow-mediated vasodilatation (FMD) of the brachial artery using B-mode ultrasound. Resting brachial artery diameters and blood flow scans were obtained before and after the administration of sublingual nitroglycerin. FMD was calculated as a ratio of the brachial artery diameter after reactive hyperemia compared to the baseline diameter, expressed as a percent change. FMD of the brachial artery was improved after ingestion of GJ and it appeared that the degree of improvement was the same regardless of whether high or low doses of GJ were ingested. Furthermore, the results revealed that adding a vitamin E supplement to the purple GJ did not further improve endothelial function.
Comment by Harold L. Karpman, MD, FACC, FACP
The "French paradox" observation has largely been attributed to the regular consumption of modest amounts of alcohol-containing beverages that were presumed to increase high density lipoprotein (HDL) cholesterol levels and inhibit platelet function.4-10 Several studies have suggested that red wine, which contains several hundred different types of flavonoids, was more cardioprotective than the alcohol-containing beverages such as beer or spirits4-7 and other studies have concluded that the observed positive effects were due to the flavonoids present in red wine and GJ.
Chou et al’s study is open to many criticisms because the sample size was extremely small, the time frame of the study was relatively short, and the brachial artery technique for evaluating endothelial function, although sensitive and reproducible, may not accurately reflect all aspects of endothelial function since it is only a simple objective measurement of FMD. Despite these shortcomings, the findings do confirm the results of other studies which suggest that pharmaceutical agents and/or natural food substances may be capable of altering endothelial function in a positive way. The validity of the results were also somewhat enhanced by the fact that each subject’s baseline brachial artery reactivity (ie, FMD) served as a control value and was compared with the results obtained in the same individual after GJ ingestion.
In summary, ingesting moderate amounts of purple GJ each day appeared to improve endothelial function as measured by FMD in patients with known arteriosclerotic coronary arterial disease. Despite the high-glucose content (ie, 56-112 g of carbohydrate) in the ingested GJ, adverse effects on lipid and glucose metabolism did not occur. If the results of this study can be reduplicated in larger groups of patients and especially, if outcome studies demonstrate a decrease in cardiovascular events as a result of ingesting GJ, the time may come when physicians will be recommending the daily ingestion of GJ alone or possibly even in combination with moderate amounts of alcoholic beverages.
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Dr. Karpman, Clinical Professor of Medicine, UCLA School of Medicine, is Associate Editor of Internal Medicine Alert.