Blueberries Improve Endothelial Function, but Not Blood Pressure, in Adults with Metabolic Syndrome: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Abstract

Blueberry consumption has been shown to have various health benefits in humans. However, little is known about the effect of blueberry consumption on blood pressure, endothelial function and insulin sensitivity in humans. The present study investigated the role of blueberry consumption on modifying blood pressure in subjects with metabolic syndrome. In addition, endothelial function and insulin sensitivity (secondary measurements) were also assessed. A double-blind and placebo-controlled study was conducted in 44 adults (blueberry, n = 23; and placebo, n = 21). They were randomized to receive a blueberry or placebo smoothie twice daily for six weeks. Twenty-four-hour ambulatory blood pressure, endothelial function and insulin sensitivity were assessed pre- and post-intervention. The blood pressure and insulin sensitivity did not differ between the blueberry and placebo groups. However, the mean change in resting endothelial function, expressed as reactive hyperemia index (RHI), was improved significantly more in the group consuming the blueberries versus the placebo group (p = 0.024). Even after adjusting for confounding factors, i.e., the percent body fat and gender, the blueberry group still had a greater improvement in endothelial function when compared to their counterpart (RHI; 0.32 ± 0.13 versus −0.33 ± 0.14; p = 0.0023). In conclusion, daily dietary consumption of blueberries did not improve blood pressure, but improved (i.e., increased) endothelial function over six weeks in subjects with metabolic syndrome.

Bioavailability of wild blueberry (poly)phenols at different levels of intake

“…In recent years, blueberries have received much attention due to their positive role in human health and disease prevention [8]. For example, blueberry consumption has been shown to improve endothelial function in young healthy men and in people with metabolic syndrome [9,10], and decrease blood pressure and arterial stiffness in pre-and hypertensive postmenopausal women and people with the metabolic syndrome [11,12]. Increasing evidence also suggests that the high polyphenol content of berries may be responsible for their beneficial effects [8,9,[13][14][15][16][17][18].…”

Where are we with Smoothies? A Review of the Latest Guidelines, Nutritional Gaps and Evidence

“…Equally, UK NDNS analysis shows that fibre intakes are consistently lower than guidelines across adults aged 20 to 59 years (an average of 18.5 g/day), with the updated AOAC fibre guidance of 30 g of fibre daily widening this gap even further [7]. Other work suggests that smoothies could have satiety effects [16] and possible benefits on endothelial function [23].…”

“…Stull et al [23] DB RCT. Allocated to receive a blueberry or placebo smoothie twice daily for six weeks.…”

The effects of 100% wild blueberry (Vaccinium angustifolium) juice consumption on cardiometablic biomarkers: a randomized, placebo-controlled, crossover trial in adults with increased risk for type 2 diabetes

“…Four randomized, parallel design human trials have reported that consumption of blueberries may beneficially affect insulin sensitivity and other early biomarkers of cardiovascular disease, such as blood pressure, endothelial function, and oxidative stress [6][7][8][9]. A systematic review has further concluded that there is a lack of clinical trials evaluating blueberry consumption in humans at risk for disease [10].…”