Eight weeks of supplementation with a high-dose of the extract were associated with significant reductions in 24-hour systolic blood pressure in pre-hypertensive people of about 3.3 mmHg, report scientists from the Korea University Anam Hospital and the Gochang Black Raspberry Research Institute in Korea.
Data published in Nutrition also indicated that the high-dose supplement decreased night-time systolic blood pressure by an average of 5.4 mmHg over eight weeks, compared to placebo.
“Reduction in systolic blood pressure by 4.5 to 6.7 mmHg would be clinically more meaningful when considering the mortality benefit of a large population with prehypertension,” wrote the researchers.
The study adds to an ever growing body of science to support the potential heart health benefits of black raspberries, with the bioactives proposed to be anthocyanins, flavonols, resveratrol, allagitannnin, and tannins.
Commenting on the potential mechanism(s), the researchers noted that the polyphenol extract may up-regulate the expression of eNOS and boost the release of nitric oxide (NO), a potent vasodilator.
However, measures of blood flow and levels of inflammatory biomarkers were unaffected by the supplementation intervention, according to findings published
The Korea-based scientists recruited 45 people with prehypertension to participate in their study. The participants were randomized assigned to one of three groups: Placebo, or moderate- or high-dose black raspberry capsules with 187.5 mg and 312.5 mg per day of raspberry powder, respectively. These two doses were equivalent to 1,500 mg and 2,500 mg of raspberries per day.
After eight weeks of intervention the results indicated that the high-dose group experienced significant reductions in 24-hour and night-time systolic blood pressure, compared to placebo.
On the other hand, no significant changes were observed in the other measures, including pulse wave velocity, abdominal visceral fat, or inflammatory biomarkers such as IL-6, TNF-alpha, C-reactive protein, sICAM-1, or sVCAM-1.
“The use of black raspberry significantly lowered 24 hour blood pressure in prehypertensive patients during the 8-week follow-up.
“Black raspberry used as a dietary supplement could be beneficial in reducing systolic blood pressure in pre-hypertensive patients,” they concluded.
The study was funded by the Gochang Black Raspberry Research Institute.
Published online ahead of print, doi: 10.1016/j.nut.2015.10.014
“Effects of Rubus occidentalis extract on blood pressure in subjects with prehypertension: randomized, double-blinded, placebo controlled clinical trial”
Authors: H.S. Jeong, et al.