In April 2015 researchers from The Netherlands published the results of their study to assess the effect of two grape extracts (grape-red wine and grape alone) on blood pressure and vascular function. Both extracts had high concentrations of anthocyanins and flavanols, but the grape alone was relatively poor in catechins and procyanidins. Over a 4-week period 60 untreated, mildly hypertensive individuals received first one grape extract and then the other. Results showed that the grape-wine extract significantly lowered 24-hour blood pressure levels, especially during the daytime, and that the blood concentration of the vasoconstrictor endothelin-1 decreased by 10%. However, other measures of vascular function were not affected. Grape juice extract alone had no effect on blood pressure levels nor on any measures of vascular function.
Draijer R et al. Consumption of a polyphenol-rich grape-wine extract lowers ambulatory blood pressure in mildly hypertensive subjects. Nutrients. 2015 Apr 30;7(5):3138-53