Written by Greg Arnold, DC, CSCS. Compared to placebo, daily consumption of grape polyphenols for 30 days significantly improved vascular endothelial function and biomarkers of metabolic syndrome by increasing flow-mediation dilation response by 45 % and lowering systolic blood pressure by 4.7%.
Metabolic syndrome is characterized by having several cardiovascular conditions that include increased blood pressure (systolic blood pressure (the top number) ≥ 130 mm Hg or diastolic blood pressure (the lower number) >85 mm Hg), high blood sugar levels (fasting plasma glucose ≥ 100 milligrams/deciliter), abnormal blood fats (triglyceride levels ≥ 150 milligrams/deciliter), excess waist circumference (≥ 102 centimeters or 40 inches for males, ≥ 88 centimeters or 36 inches for females), and abnormal cholesterol levels (reduced HDL (“good”) cholesterol: < 40 milligrams/deciliter in males and < 50 milligrams/deciliter in females). Combined, all of these health parameters increase the risk of heart disease, heart attack, and stroke (1).
Once metabolic syndrome has been diagnosed, lifestyle changes that include regular exercise, losing weight, quitting smoking, and improving diet (2) are recommended. Now, a new study (3) suggests that grape polyphenols may help with blood pressure health in those with metabolic syndrome.
In the study, 24 men between the ages of 30 and 70 with metabolic syndrome were given either 46 grams of freeze-dried grape polyphenol powder (containing 266.8 milligrams of total phenols and was equivalent to two servings of grapes per day) or a placebo each day for 30 days. They then waited three weeks (called the “washout period”) and switched treatment groups for another 30 days. Participants were asked to maintain their usual diet and physical activity during the study and not consume any polyphenol-rich foods.
Before and after each 30-day period, the researchers measured the participants’ blood pressure, a measure of blood vessel health called “flow-mediated dilation” of the main blood vessel in the arm (the brachial artery) and obtained blood samples to measure two inflammatory proteins, sICAM-1 and sVCAM-1. Finally, the researchers measured the waist circumference of each participant to see if they would drop below the 102-cm threshold to classify for metabolic syndrome.
The researchers found that those in the grape polyphenol group had a 4.7% lower systolic blood pressure (the top number) compared to the placebo group (122 vs. 128 mm Hg, p < 0.0025) while 71% of those in the placebo groups had a waist circumference >102 cm compared to 54% of those in the grape polyphenol group. For sICAM-1 levels, those in the polyphenol group concentrations had 6% lower levels compared to the placebo group (142 vs. 151 milligrams/Liter, p < 0.025), showing a lower level of inflammation in the grape polyphenol group. No differences were seen with the other inflammatory marker, sVCAM-1. Finally, flow-mediated dilation was 42.5% greater in the grape group compared to the placebo group (5.7 vs. 4.0%, p < 0.001), indicating greater blood vessel relaxation responses.
For the researchers, “compared with placebo, the daily consumption of grape polyphenols for 30 days significantly improved vascular endothelial function and biomarkers of metabolic syndrome by increasing flow-mediation dilation response, lowering systolic blood pressure, and decreasing circulating inflammatory molecules.”
Source: Barona, Jacqueline, et al. “Grape polyphenols reduce blood pressure and increase flow-mediated vasodilation in men with metabolic syndrome.” The Journal of nutrition 142.9 (2012): 1626-1632.
© 2012 American Society for Nutrition
Posted March 23, 2013.
Greg Arnold is a Chiropractic Physician practicing in Hauppauge, NY. You can contact Dr. Arnold directly by emailing him at PitchingDoc@msn.com or visiting his web site at www.PitchingDoc.com
References:
- Alberti KG, Eckel RH, Grundy SM, et al. 2009. Harmonizing the metabolic syndrome: a joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention; National Heart, Lung, and Blood Institute; American Heart Association; World Heart Federation; International Atherosclerosis Society; and International Association for the Study of Obesity. Circulation 120: 1640–1645.
- Grundy SM, Brewer HB, Jr., Cleeman JI, Smith SC, Jr., Lenfant C. 2004a. Definition of metabolic syndrome: report of the National Heart, Lung, and Blood Institute/American Heart Association conference on scientific issues related to definition. Arterioscler Thromb Vasc Biol 24: e13‐18.
- Barona J. Grape Polyphenols Reduce Blood Pressure and Increase Flow-Mediated Vasodilation in Men with Metabolic Syndrome. J Nutr 2012; 142(9):1626-1632.
