Blueberries and Blood Vessel Protection 

FOR IMMEDIATE RELEASE

New Research Illustrates that Daily Consumption of Blueberries May Improve Endothelial Function in Postmenopausal Women with High Blood Pressure 

FOLSOM, Calif. – February 28, 2023 – A new research study published in Food & Function during American Heart Month found that daily consumption of blueberries for 12 weeks, consumed as 22 g/day of freeze-dried highbush blueberry powder (equivalent to one cup of fresh blueberries), improves endothelial function in postmenopausal women with elevated blood pressure or stage 1-hypertension [1].  

The endothelium is a single layer of cells, called endothelial cells, which line the blood vessels and lymphatic vessels (e.g., arteries, veins, capillaries). It supports healthy blood flow [2]. An impairment in endothelial function is referred to as endothelial dysfunction, which is antecedent to atherosclerosis and centrally contributes to its progression [3]. 

Elevated blood pressure and hypertension are also contributors to cardiovascular disease [4] [5]. 75% of postmenopausal women are estimated to have hypertension, which worsens endothelial function by increasing oxidative stress (a harmful condition that happens when your body has too many free radicals and not enough antioxidants to fight them off) and inflammation [6] [7]. 

This randomized, double-blind, placebo-controlled, parallel-arm clinical trial found that blueberries protect blood vessels partly through the mechanism of reducing oxidative stress. Blueberries contain phytochemicals (i.e., naturally occurring plant chemicals) called polyphenols. In particular, anthocyanins, which are a type of polyphenols that give blueberries their beautiful blue color, have been studied for their health benefits such as their heart health benefits and antioxidant effects. These findings are noteworthy considering the high prevalence of endothelial dysfunction in a postmenopausal population and its central role in cardiovascular disease, the leading cause of death in the United States and globally [8].  

“This is the first study of its kind assessing the effects of daily blueberry consumption on endothelial function and oxidative stress-mediated suppression of endothelial function in postmenopausal women with elevated blood pressure or hypertension,” said Sarah A. Johnson, PhD, RDN, Associate Professor and Director Functional Foods & Human Health Laboratory in the Department of Food Science and Human Nutrition at Colorado State University and the study’s lead investigator. “Blueberries are a source of polyphenols like anthocyanins which are associated with heart health.”  

The study, which was supported by a grant from the U.S. Highbush Blueberry Council, along with funding from the United States Department of Agriculture, builds on previous research from Johnson and her team that demonstrated that consuming 22 g of freeze-dried blueberry powder (equal to 1 cup of fresh blueberries) daily for 8 weeks led to improvements in systolic and diastolic blood pressure and brachial-ankle pulse wave velocity (PWV; a measure of arterial stiffness), and increased plasma concentrations of nitric oxide metabolites in postmenopausal women with high blood pressure, also suggestive of improved endothelial function [9]. 

“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,” was conducted at Colorado State University by an interdisciplinary team of investigators between 2017 and 2022. Estrogen-deficient postmenopausal women aged 45-65 years with elevated blood pressure or stage 1-hypertension (total n=43, subjects with endothelial function assessments n=32) were randomly assigned to consume 22 g/day of freeze-dried highbush blueberry powder (equivalent to one cup of fresh blueberries) or placebo powder for 12 weeks. Endothelial function was assessed at baseline and 12 weeks through ultrasound measurement of brachial artery flow-mediated dilation (FMD) which is a measure of endothelium-dependent dilation. Other measures of cardiovascular health were performed, and plasma polyphenol metabolites were assessed at baseline and 4, 8, and 12 weeks. 

Participants were asked to maintain their usual diet and physical activity patterns, and to keep fresh and frozen blueberry consumption to less than or equal to 2 cups a week for the duration of the study (with the exception of the treatment intervention). The participants self-reported their treatment. 

To determine whether daily blueberry consumption improves endothelium-dependent dilation by suppressing oxidative stress, brachial artery FMD was measured before and after an intravenous infusion of a high dose of ascorbic acid (Vitamin C), a potent antioxidant that scavenges reactive oxygen species, including free radicals.  

The results illustrate that blueberries significantly improve endothelial function, but not blood pressure, in postmenopausal women with elevated blood pressure or stage 1-hypertension. More specifically, absolute FMD/SR_AUC 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/SR_AUC from baseline to 12 weeks was higher (p<0.03) than the placebo group. Normalization of FMD to SR_AUC has been validated in numerous research studies and has been recommended for use in research [10] [11]. This is a clinically meaningful finding considering endothelial dysfunction is a strong predictor of cardiovascular disease and events independent of blood pressure. Additionally, after 12 weeks of blueberry consumption (but not placebo), the improvement in endothelial function following ascorbic acid infusion was significantly lower than the response at baseline, indicating that improvements in endothelial function were mediated by reductions in oxidative stress. There were also significant increases in plasma polyphenol metabolites, including those produced by interactions with the gut microbiota, suggesting potential mechanisms.   

Future studies evaluating blueberry consumption in diverse populations including men and women are warranted to provide additional insight into efficacy and physiological mechanisms, as well as to understand factors contributing to inter-individual variability in clinical responses. Additionally, more research is needed to better understand the antihypertensive effects of blueberries, and factors that can be modified and/or implemented to improve efficacy as part of a precision nutrition approach. 

“While further studies are warranted, the results of this study suggest that a single cup daily serving of blueberries can improve endothelial function through reduced oxidative stress, which is important for heart disease risk reduction in postmenopausal women,” said Johnson. 

This manuscript was recently selected for the Food & Function 2023 “HOT” article collection. The collection will be part of a special issue being released in celebration of the International Conference on Polyphenols and Health, to highlight the latest trends, topics and developments in the field. 

The USHBC had no role in study design, data collection, data analysis, data interpretation, or writing of the study. For more information on blueberry nutrition research visit blueberrycouncil.org/health-professionals/health-research/. 

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About the U.S. Highbush Blueberry Council

The U.S. Highbush Blueberry Council is an agriculture promotion group, representing blueberry growers and packers in North and South America who market their blueberries in the United States and overseas, and works to promote the growth and well-being of the entire blueberry industry. The blueberry industry is committed to providing blueberries that are grown, harvested, packed and shipped in clean, safe environments. Learn more at blueberry.org.