“The results of the clinical trials that used grape seed extract in capsule form produced nice drops in blood pressure,” said Britt Burton-Freeman, PhD and director of the Center for Nutrition Research at the Illinois Institute of Technology Institute of Food Safety and Health, Chicago, who worked on the trial. “We wanted to see whether it would work when put into a beverage, and it looks like it works very well. It wasn’t that much of a surprise, because if grape seed extract is working, it should work when delivered in a beverage, too.”
In a randomized, double-blind, 10-week parallel design study, Dr. Burton-Freeman and other researchers from IIT’s Center for Nutrition Research and the University of California-Davis dispensed a daily 300 mg dose of MegaNatural-BP grape seed extract in two 40kcal beverages per day to 12 pre-hypertensive men and women (in the 120-139 systolic range or the 80-89 diastolic range) ages 25 to 65 over a six-week period. Sixteen received the placebo. Their blood pressure levels were assessed at the end of the treatment and again four weeks later after they’d returned to their normal routines.
“The big news with the beverage was the systolic blood pressure in the whole population dropped 7 mm of mercury after six weeks,” Dr. Burton-Freeman told NutraIngredients-USA. “Then there was an increase after 10 weeks, when they stopped taking the grape seed extract, so we saw a nice little rebound effect. The diastolic blood pressure of the population dropped by 3.8 mm of mercury as well,” she said.
Higher starting BP group saw more 'robust' effect
More notably though, was that there was a subset of participants who responded better than others, according to the study abstract. The portion of the population that was at or above the median systolic blood pressure of 125 experienced systolic blood pressure drop of 13.6 mm of mercury, “so we saw a really robust effect in that group,” Dr. Burton-Freeman said. “The efficacy almost doubled among people with a higher starting blood pressure, which makes sense because if you’re in more critical condition, there’s more room to reduce your blood pressure back to normal.”
Similarly, those with diastolic blood pressure at or above the median split of 83.5 also had a higher blood pressure drop, of 5.8 mm of mercury versus the lower group, in which “little happened,” she said. “Again, the take-home is the higher starting systolic or diastolic blood pressure group got the greatest benefit. We didn’t see the same effect in the lower group. They saw some benefit, just not as robust.”
Dr. Burton-Freeman presented the results this week at the VI International Conference on Polyphenols in Buenos Aires, Argentina, and she and the team will submit a manuscript for publication in a peer-reviewed journal in November.
A byproduct of the study that will require further research is the possibility that grape seed extract could aid in glucose control through improved insulin sensitivity, Dr. Burton-Freeman said. “Because we were assessing metabolic changes in participants, we saw some clues as to the mechanisms of action,” she said. “We looked at glucose, oxidized LDL, insulin—and we had these drops in fasting insulin after six weeks of treatment.”
But the changes in insulin were marginally significant. “There is some data to suggest that changes in insulin sensitivity will experience benefits on blood pressure through some established mechanism, though it’s not all fettered out. We’re going forward with trying to understand that relationship, that mechanism related to the change.”
Source: Grape seed extract delivered in a beverage: effects on blood pressure and metabolic endpoints in individuals with pre-hypertension
Authors: Burton-Freeman B., Park E., Huang Y., Edirisinghe I. Illinois Institute of Technology, Center for Nutrition Research, Chicago, IL and University of California, Davis, Davis, CA.