Effect of Concord Grape Juice on Endothelial Function

Inclusion Criteria: * Body mass index ≥ 25 and \< 40 kg/m2 * Age ≥ 50 years * Otherwise healthy Exclusion Criteria: * Clinical diagnosis of atherosclerotic vascular disease. * Clinical history of diabetes mellitus or fasting glucose ≥126 mg/dl * Uncontrolled hypertension * Treatment with an investigational new drug within the last 30 days * Clinical history of other major illness including end-stage cancer, renal failure, hepatic failure, or other conditions that in the opinion of the principal investigator make the study inappropriate * Psychological illness or condition such as to interfere with the subject's ability to understand the requirements of the study * Use of Vitamin E, Vitamin C, beta carotene, lipoic acid, or other food or herbal supplements within 1 month of enrollment. Subjects taking multivitamins or other forms of vitamin E and C in doses that do not exceed two times the recommended daily allowance will not be excluded * Extreme dietary habits (i.e. Atkins, very high protein/low carbohydrate, or vegan diet