Impaired vasodilation is thought to be one of the earliest manifestations of heart disease.
Previous clinical studies on red wine have produced similar outcomes, leading some researchers to speculate that the alcohol content is the factor that protects against heart disease. It is also likely that white grape juice and white wine provide fewer benefits because they contain mainly juice, without the healthful components from the grape seeds and skins. Ten participants had a history of high blood pressure or were taking antihypertensive medication, and 11 people had high cholesterol levels or were receiving cholesterol-lowering treatment. In addition, most of the participants had been taking vitamins E and C, antioxidant therapies that may also have an effect on heart health. People with unstable angina, uncontrolled diabetes mellitus, or recent medication changes were not allowed to participate in the study.