Conducted by UC Davis cardiovascular researchers, the study was the first human clinical trial to assess the effect of grape seed extract on people with metabolic syndrome, a combination of risk factors that increase the risk for heart disease, including high blood pressure, excess abdominal body weight, high blood cholesterol fats and high blood sugar. The researchers will present the results at the American Chemical Society Meeting and Exposition on March 26 in Atlanta, and at the Federation of American Societies for Experimental Biology's 2006 meeting in San Francisco April 2.
It is estimated that 40 percent of American adults, or 50 million people, have metabolic syndrome.
The one-month study involved 24 male and female patients diagnosed with metabolic syndrome. The patients were divided into three groups of eight. The first group received a placebo, while the second and third groups received 150 milligrams and 300 milligrams, respectively, of a new grape seed extract. All participants' blood pressure was automatically measured and recorded for 12 hours after ingestion.
"Participants in the two groups receiving grape seed extract experienced an equal degree of reduced blood pressure. The average drop in systolic pressure was 12 millimeters. The average drop in diastolic pressure was 8 millimeters," said the study's lead researcher, C. Tissa Kappagoda, professor of cardiovascular medicine and director of the Preventive Cardiology Program at UC Davis.
Kappagoda adds that the group taking 300 milligrams of grape seed extract also had reduced serum oxidized LDL cholesterol levels.
"Generally, the higher their initial oxidized LDL level was, the greater the drop by the end of the study," he said. The extract has received the GRAS (generally recognized as safe) certification from the FDA and has no known side effects.
The UC Davis research team recently has recently embarked on a second placebo-controlled human clinical study of grape seed extract, looking at its benefits for pre-hypertension patients with systolic pressure of 120-139 mmHg, and diastolic blood pressure of 80-89 mmHg. Three previous studies in animal models by this team have indicated that grape seed extract may also prevent atherosclerosis.
Polyphenolics, a division of Constellation Wines U.S., Inc., funded and supplied the grape seed extract for the study.