Consuming grapes may help protect heart health in people with metabolic syndrome, according to new research published in the Journal of Nutrition. Researchers observed a reduction in key risk factors for heart disease in men with metabolic syndrome: reduced blood pressure, improved blood flow and reduced inflammation. Natural components found in grapes, known as polyphenols, are thought to be responsible for these beneficial effects.
The randomized, placebo-controlled, crossover study, led by principal investigator Dr. Maria Luz Fernandez and Jacqueline Barona, a PhD student in Dr. Fernandez' lab at the Department of Nutritional Sciences of the University of Connecticut, recruited men between 30 and 70 years of age with metabolic syndrome. The study is believed to be the first to look at the impact of grapes on metabolic syndrome.
Metabolic syndrome is a cluster of conditions that occur together – increased blood pressure, a high blood sugar level, excess body fat around the waist or low HDL (the good cholesterol) and increased blood triglycerides – significantly increasing the risk for heart disease, stroke and diabetes. Metabolic syndrome is a major public health concern, and is on the rise in the U.S.
In this study, participants were randomly assigned to consume grapes, in the form of a freeze-dried whole grape powder, or a placebo powder, for four weeks. Then, following a 3-week "washout" period where neither grapes nor placebo were consumed, individuals were allocated to the alternate treatment. This powerful study design allowed investigators to compare the response of each individual to consumption of both the placebo and grapes.
The study results showed that for each of the study's subjects, grape consumption resulted in significant decreases in blood pressure, improved blood flow (greater vasodilation), and decreases in a compound associated with inflammation.
"These results suggest that consuming grapes can improve important risk factors associated with heart disease, in a population that is already at higher risk," said Fernandez. "This further supports the accumulating evidence that grapes can positively influence heart health, and extends it to men with metabolic syndrome."
The California Table Grape Commission was created by the California legislature in 1967 to increase worldwide demand for fresh California grapes through a variety of research and promotional programs.
 Barona, J, Fernandez, ML, et al. Grape polyphenols reduce blood pressure and increase flow-mediated vasodilation in men with metabolic syndrome. Published ahead of print J Nutr. 2012 doi:10.3945/jn.112.1162743