Effects of A Standardized, Freeze-Dried Grape Powder in Adults with Metabolic Syndrome

Diets rich in fruits and vegetables have been correlated to lower disease risk. This is thought to be due to bioactive components such as: vitamin C, vitamin E, carotenoids, and polyphenols. Grapes are a food source of many bioactive components, including polyphenols. The effects standardized, freeze-dried, grape powder (GRAPE) were examined in adults with metabolic syndrome (MetS). Twenty men and women (aged 30-70 y) were instructed to consume 60 g/day of GRAPE (equivalent to 2.5 cups fresh grapes daily) or nutritionally-matched placebo powder in a randomized, placebo-controlled, crossover intervention study for 13 weeks. This included 2-week run-in, 4-week intervention (GRAPE or placebo), 3-week washout, and final 4-week intervention (alternate powder) phases. Subjects did not significantly alter their diets when comparing GRAPE and placebo. Plasma lipids, glucose, and alanine aminotransferase (ALT), saw no significant changes when comparing GRAPE to placebo. GRAPE slightly, but significantly, decreased BMI compared to placebo. In men, it was seen that plasma triglycerides (TG) and pulse were significantly reduced by GRAPE vs. placebo. In females, an increase in plasma cholesterol was observed with GRAPE ingestion. Markers of oxidative stress, measured as advanced oxidative protein products (AOPPs), or thiobarbituric acid reactive substances (TBARS), were not different when comparing GRAPE with placebo. Plasma inflammation markers TNF-α, IL-6, and MCP-1 also saw no significant changes between treatments, although TNF-α tended to be lower with GRAPE. No significant differences were seen between groups for plasma insulin and HOMA-IR score. However, plasma TBARS, insulin, and HOMA-IR were significantly increased with GRAPE compared to placebo only in women. These results suggest that GRAPE may favorably influence BMI, but has sex-dependent effects on cardiometabolic risk factors associated with MetS