Abstract
BackgroundBlueberries contain high levels of polyphenolic compounds with high in vitro antioxidant capacities. Their consumption has been associated with improved vascular and metabolic health.PurposeThe objective was to examine the effects of blueberry supplement consumption on metabolic syndrome (MetS) parameters and potential underlying mechanisms of action.MethodsA randomized double-blind placebo-controlled intervention trial was conducted in adults at risk of developing MetS. Participants consumed 50 g daily of either a freeze-dried highbush blueberry powder (BBP) or a placebo powder for 8 weeks (n = 49). MetS phenotypes were assessed at weeks 0, 4 and 8. Fasting blood gene expression profiles and plasma metabolomic profiles were examined at baseline and week 8 to assess metabolic changes occurring in response to the BBP. A per-protocol analysis was used.ResultsA significant treatment effect was observed for plasma triglyceride levels that was no longer significant after further adjustments for age, sex, BMI and baseline values. In addition, the treatment*time interactions were non-significant therefore suggesting that compared with the placebo, BBP had no statistically significant effect on body weight, blood pressure, fasting plasma lipid, insulin and glucose levels, insulin resistance (or sensitivity) or glycated hemoglobin concentrations. There were significant changes in the expression of 49 genes and in the abundance of 35 metabolites following BBP consumption. Differentially regulated genes were clustered in immune-related pathways.ConclusionAn 8-week BBP intervention did not significantly improve traditional markers of cardiometabolic health in adults at risk of developing MetS. However, changes in gene expression and metabolite abundance suggest that clinically significant cardiometabolic changes could take longer than 8 weeks to present and/or could result from whole blueberry consumption or a higher dosage. BBP may also have an effect on factors such as immunity even within a shorter 8-week timeframe.Clinical trial registrationclinicaltrials.gov, NCT03266055, 2017
Highlights
With an estimated prevalence of almost 35% in the USA [1] and 19% in Canada [2], metabolic syndrome (MetS) is a condition of great concern in developed countries
Participants characteristics and adherence Of the 110 individuals screened for eligibility, 59 participants were included in this randomized double-blind, placebocontrolled intervention trial, with analyses conducted on a final sample of 49 individuals who consumed the blueberry powder (BBP) (n = 25) or the placebo powder (n = 24) (Fig. 2)
Results from the side effects questionnaire indicated that participants experienced some minor side effects with both the BBP and placebo powder (Supplementary Figure 1), but these side effects were generally tolerable with only one participant dropping out of the study as a result of persistent abdominal discomfort
Summary
With an estimated prevalence of almost 35% in the USA [1] and 19% in Canada [2], metabolic syndrome (MetS) is a condition of great concern in developed countries. Insulin resistance (IR), dyslipidemia and hypertension, people with MetS are at higher risk of developing type 2 diabetes and cardiovascular disease [3]. Oxidative stress is a commonality for these risk factors and is suspected of playing a proinflammatory role promoting their development [4]. Oxidative stress occurs when the body’s antioxidant defenses are not sufficient to counterbalance production of free radicals and other reactive oxygen species (ROS) [4]. Blueberries contain high levels of polyphenolic compounds with high in vitro antioxidant capacities. Their consumption has been associated with improved vascular and metabolic health. Purpose: The objective was to examine the effects of blueberry supplement consumption on metabolic syndrome (MetS) parameters and potential underlying mechanisms of action
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