CONDUCTED BY: Pennington Biomedical Research Center, Louisiana State University System; Center for the Study of Botanicals and Metabolic Syndrome, Pennington Biomedical Research Center, Louisiana State University System, USA; Baton Rouge VA Outpatient Clinic, Southeast Louisiana Veterans Health Care System,Essen Park Avenue, USA; Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Philadelphia.
PUBLISHED ON: Nutrients
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.
In conclusion, six weeks of blueberry consumption on a daily basis did not improve blood pressure in a population with metabolic syndrome. Furthermore, the secondary outcome variable insulin sensitivity was unaffected. However, there was evidence of improved vascular health with the demonstration that endothelial function was improved (i.e., increased). This indicates that consumption of blueberries may increase endothelial function, even though blood pressure and other variables studied were not significantly affected. Although more validation trials are needed to fully evaluate this observation, our study does suggest a favorable benefit of blueberries on vascular health over a six-week period in adults with metabolic syndrome. Like most botanical and nutrition intervention studies, there is a substantial amount of inter-individual variability among the participants consuming the same dose of the botanical or nutritional product. Thus, future studies should evaluate the metabolomic and transcriptomic profiles of responders versus nonresponders to elucidate the different physiologic pathways that are affected by consuming blueberries. Furthermore, clinical trials with a longer duration (>8–12 weeks) evaluating the effects of blueberries or anthocyanin-rich foods on endothelial function and blood pressure prior to the study, mid-study and end of the study are warranted to explain the potential role in improving endothelial function and blood pressure in a population at high risk for developing CVD.