Effects of grape seed extract beverage on blood pressure and metabolic indices in individuals with pre-hypertension: a randomised, double-blinded, two-arm, parallel, placebo-controlled trial

Abstract

The aim of the present study was to test grape seed extract (GSE) as a functional ingredient to lower blood pressure (BP) in individuals with pre-hypertension. A single-centre, randomised, two-arm, double-blinded, placebo-controlled, 12-week, parallel study was conducted in middle-aged adults with pre-hypertension. A total of thirty-six subjects were randomised (1:1) to Placebo (n 18) or GSE (n 18) groups; twenty-nine of them completed all the protocol-specified procedures (Placebo, n 17; GSE, n 12). Subjects consumed a juice (167 kJ (40 kcal)) containing 0 mg (Placebo) or 300 mg/d GSE (150 mg) twice daily for 6 weeks preceded by a 2-week Placebo run-in and followed by 4-week no-beverage follow-up. Compliance was monitored. BP was measured at screening, 0, 6 and 10 weeks of intervention and blood samples were collected at 0, 3, 6 and 10 weeks of intervention. GSE significantly reduced systolic BP (SBP) by 5·6 % (P=0·012) and diastolic BP (DBP) by 4·7 % (P=0·049) after 6 weeks of intervention period, which was significantly different (SBP; P=0·03) or tended to be different (DBP; P=0·08) from Placebo. BP returned to baseline after the 4-week discontinuation period of GSE beverage. Subjects with higher initial BP experienced greater BP reduction; nearly double the effect size. Fasting insulin and insulin sensitivity tended to improve after 6 weeks of GSE beverage supplementation (P=0·09 and 0·07, respectively); no significant changes were observed with fasting plasma lipids, glucose, oxidised LDL, flow-mediated dilation or vascular adhesion molecules. Total plasma phenolic acid concentrations were 1·6 times higher after 6 weeks of GSE v. Placebo. GSE was found to be safe and to improve BP in people with pre-hypertension, supporting the use of GSE as a functional ingredient in a low-energy beverage for BP control.