Research from Korea University Anam Hospital, in Seoul, South Korea, has found that black raspberries significantly decrease artery stiffness and increase heart-healthy endothelial progenitor cells (EPC), which assist in repairing damaged blood vessels.

The study tested 51 patients that met at least three criteria for metabolic syndrome, including waist circumference measurements, high triglycerides, low high-density lipoprotein (HDL) cholesterol levels, high blood pressure and/or symptoms of glucose intolerance. The subjects were split into two groups; one received 750 milligrams per day of black raspberry extract for 12 weeks, while the other group received a placebo.

The researchers assessed the radial artery augmentation index, a measure for blood vessel wall stiffness, and values for this measurement decreased by 5 percent in the black raspberry group. The placebo group’s levels increased by 3 percent.

In addition, EPC counts increased in the black raspberry group by 19 microliters, versus a drop of 28 microliters in the placebo group. Black raspberries contain a number of heart-healthy compounds, including phenolic acids, resveratrol, flavonoids and tannins.