Grape seed extract's blood pressure benefits extend to beverages, study shows
The human clinical trial, the third for the ingredient, was led by Britt Burton-Freeman, PhD, at the Illinois Institute of Technology in Chicago. Dr. Burton-Freeman and Dr. Eunyoung Park will be presenting the results the Experimental Biology 2013 conference being held this week in Boston.
In the double-blind, placebo-controlled study, Burton-Freeman’s team administered the ingredient in functional fruit juice beverage to prehypertensive participants. In concert with earlier study results of the ingredient, the latest results support the claim that the ingredient supports blood pressure in the healthy range.
The study results showed significant effects in lowering both systolic and diastolic blood pressure values. The results also showed changes in insulin and significant changes in HOMA value .
And, while the results fell in line with what was expected given earlier data, there were some surprises, too.
“One of the things we found that it was even more effective in those people that needed it more. The higher their blood pressure was, the more response we got out of them,” Burton-Freeman said.
Study design
In the study, 36 pre-hypertensive adults were randomized to drink either a beverage formulated with MegaNatural-BP or a placebo daily for six weeks. Individuals in the control group were measured 10 weeks after cessation of the intervention as well.
Ambulatory (12 hr, day) BP before and after 6 week consumption of GSE beverage (300 mg/day) or placebo beverage was measured in randomized parallel design (n=36, 1:1). Means of age, BMI and initial systolic (S)/diastolic (D) BP were 42±10 y, 32±8 kg/m2, and 128±8/83±7 mmHg, respectively.
Significant reductions in SBP (GSE -7.4±2.3 vs placebo 1.6±1.9 mmHg, p=0.003) and DBP (GSE -3.8±1.6 vs placebo 0.7±1.3 mmHg, p=0.03) were observed after 6 weeks GSE beverage compared to the placebo beverage. The effectiveness of GSE was improved in subjects with SBP above the median (≥ 125 mmHg) (GSE -14 ± 2.5 vs placebo -0.6±2.2 mmHg, p<0.05) and in subjects with DBP above the median (≥ 83 mmHg) (GSE -5.7±1.9 vs placebo 0.7±1.4 mmHg, p<0.05). Changes in insulin (p=0.07) and significant changes in HOMA value (p<0.05) were found after 6 weeks GSE beverage compared to the placebo beverage.
Future study directions
Burton-Freemen said future research directions on the ingredient will be to further define precisely how the ingredient is absorbed and, further, how it achieves its promising results.
“One of the things that hasn’t been ferreted out real well is the pharmacokinetics of the components. The polyphenols that are in the grape seed extract are mostly complex tannins. There are some simpler ones, too. The simple ones get absorbed early.
“Then you gave these the bigger molecules that make it to the lower bowel where we think they are getting metabolized. So you get a later phase metabolite uptake. That’s data that we are investigating right now,” Burton-Freeman said.
“From our in vitro studies we believe it is working through a redox mechanism. We believe that is is a nitric oxide dependent effect and we know that the endothelium is critical to the effect. But we don’t fully know if that is accounting for 100% of the effect. There is some recent data that indicates there might be some activity at the level of the kidneys. What we have right now is data that came from in vitro and ex vivo experiments,” she said.
MegaNatural BP, as it is included in a capsule, is an very bitter and astringent substance, Burton-Freeman said. But she said the formulators at Polyphenolics seemed to have conquered that issue, as they supplied a pleasant-tasting fruit beverage that resembled apple juice, save for its purple color.
Dr. Burton-Freeman is the director of the Center for Nutrition Research and Assistant Professor Research in Biology, Center for Nutrition Research, Institute of Food Safety and Health at the Illinois Institute of Technology.
Polyphenolics, based in Madera, CA, is a division of Constellation Brands.
