Blueberry and cardiovascular disease risk factors: A systematic review and meta-analysis of randomized controlled trials

Abstract

Background and aims: Cardiovascular disease (CVD) remains an important cause of mortality and morbidity that can be prevented by the consumption of healthy foods. These include blueberry, a dark coloured berry containing extremely high amounts of functional ingredients. We therefore examined the extent to which supplementation with blueberry effects on CVD risk indices. Methods: We searched the ISI Web of Science, Scopus, PubMed and Cochrane Library on March 2020 and checked reference lists from primary studies and review articles for any additional studies. No language restrictions were applied. All randomized and controlled clinical trials (RCTs) using blueberry supplements to modify CVD risk factors were included in our analysis. Results: Mean Difference (MD) was pooled using a random effects model and 11 studies were included in the final analysis. Pooled effect size showed that supplementation with blueberry had a small insignificant effect in reducing plasma triglycerides (MD = -0.27 mmol/l; 95 CI: -0.57, 0.17, p = 0.06). Although current study found no differences between blueberry and control groups for any other outcomes, subgroup analysis suggested a favourable impact of blueberry on reducing body weight. Significant weight loss was indicated from studies longer with a follow up of more than 6 weeks or with blueberry powder or freeze-dried blueberry. Conclusion: Current evidence is insufficient to show a benefit of blueberry supplements in modifying CVD risk factors across a variety of adult populations. Robust data and larger studies are required to assess potential effects.