Blueberry Consumption Improves Endothelial Function in Post-Menopausal Women

by | May 16, 2023 | Blood Pressure, Cardiovascular Health, Fruits and Vegetables, Women's Health

Written by Taylor Woosley, Staff Writer. 12-week supplementation of 22 g daily of freeze-dried blueberry powder resulted in a 96% increase in FMD/SRAUC compared to baseline (p < 0.05) and was unchanged in the placebo group (p > 0.05). 

fruits and vegetables - blueberriesCardiovascular disease (CVD) is the leading cause of mortality and morbidity worldwide1. Aging is associated with a steady rise in incident CVD in women and approximately 75% and 78% of postmenopausal women aged 65 to 75 and older in the United States are hypertensive2. Menopause is characterized by a decrease in endogenous production of estrogen, which is associated with vascular dysfunction, increased blood pressure, redistribution of body fat toward abdominal areas, and hyperlipidemia, all of which increases CVD risk3.

Vitamins, minerals, polyphenols, and flavonoids from the diet have shown beneficial effects in improving endothelial function, blood pressure, and inflammatory markers4. Blueberries contain high contents of polyphenols, flavonoids, and anthocyanins, which are bioactive compounds believed to have the ability to provide and activate cellular antioxidant protection, scavenge free radicals, and consequently protect against oxidant-induced and inflammatory cell damage5. Prospective studies have shown that higher anthocyanin intake is associated with lower all-cause mortality, with benefits also observed for biomarkers including hypertension6.

Woolf et al. conducted a randomized, double-blind, placebo-controlled, parallel-arm study to examine the efficacy of blueberry consumption to improve endothelial function, blood pressure, and other biomarkers of cardiometabolic health in postmenopausal women with above-normal blood pressure. Study inclusion consisted of estrogen-deficient postmenopausal women aged 45-65 years with elevated blood pressure or stage 1 hypertension (systolic blood pressure 120-139 mmHg and/or diastolic blood pressure 80-89 mmHg). Primary outcomes were brachial artery flow-mediated dilation (FMD) and blood pressure. Secondary outcomes included the impact of intravenous ascorbic acid on oxidative stress-mediated suppression of endothelial function, endothelium-independent dilation, hemodynamics, arterial stiffness, plasma polyphenolic metabolites, and blood markers of cardiometabolic health.

Laboratory measures (including blood lipids, hemoglobin A1C, follicle stimulating hormone, and estradiol) were obtained on 4 different occasions separated by 4 weeks over a 12-week period with participants in a fasted state. Subjects (n=43) were randomly assigned to treatment groups using block randomization stratified by hypertension stage to receive either: 22 g freeze-dried highbush blueberry powder (equivalent to about 1 cup of fresh blueberries) or 22 g isocaloric and carbohydrate-matched placebo powder with a similar color and taste to the blueberry powder. The 22 g dose of blueberry powder contained 726 mg of total polyphenols and 224 mg of anthocyanins. Subjects consumed 11 g of their assigned treatment 2 times per day mixed in water, at least 6-8 hours apart, for 12 weeks.

Brachial artery diameter, mean blood velocity (MBV), and FMD were measured and FMD values were expressed as relative (%) changes from baseline to peak diameter and corrected for shear rate (FMD/SRAUC). Brachial artery FMD was measured before and after a supraphysiologic infusion of the antioxidant ascorbic acid to determine whether daily blueberry consumption improved endothelium-dependent dilation by suppressing oxidative stress. Furthermore, sublingual nitroglycerin (NTG) was administered to examine endothelium-independent dilation in a subset of study participants (n=20). Self-reported food intake was collected prior to each study visit to assess energy intake throughout the study. Significant findings of the study are as follows:

  • Absolute FMD/SRAUC was 96% higher (p < 0.01) at 12 weeks compared to baseline in the blueberry group with no change (p > 0.05) observed in the placebo group, and the change in FMD/SRAUC from baseline to 12 weeks was higher (p < 0.03) than the placebo group.
  • Reductions in triglycerides (p < 0.05) were observed at 12 weeks compared to baseline in the blueberry group. Additionally, the change from baseline to 12 weeks for HDL-C was higher (p < 0.05) in the blueberry group than the placebo group. Reductions in LDL-C (p < 0.05) were noted at 12 weeks compared to baseline in both groups.
  • The sum of plasma polyphenol metabolites increased at 4, 8, and 12 weeks in the blueberry group compared to baseline and were higher than the placebo group (all p < 0.05).

Results of the study show that 12-week supplementation of 22 g daily freeze-dried blueberry powder improved FMD/SRAUC and increased plasma polyphenol metabolites compared to placebo. Findings suggest that blueberry consumption improves endothelial function in post-menopausal women. Study limitations include the small sample size for certain analyses and the potential lack of generalizability of findings because the majority of subjects were White/Caucasian.

Source: Woolf, Emily K., Janée D. Terwoord, Nicole S. Litwin, Allegra R. Vazquez, Sylvia Y. Lee, Nancy Ghanem, Kiri A. Michell et al. “Daily blueberry consumption for 12 weeks improves endothelial function in postmenopausal women with above-normal blood pressure through reductions in oxidative stress: a randomized controlled trial.” Food & Function 14, no. 6 (2023): 2621-2641.

© The Royal Society of Chemistry 2023

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Posted May 16, 2023.

Taylor Woosley studied biology at Purdue University before becoming a 2016 graduate of Columbia College Chicago with a major in Writing. She currently resides in Glen Ellyn, IL.

References:

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