The Potential Effect of Blueberry on Cognitive Health and Mood State based on Human Intervention Studies: Systematic Review and Mini Meta-Analysis

Background: Blueberries are known for their high content of several bioactive compounds, specifically anthocyanin, which are the most beneficial of the flavonoid family in terms of neuroprotection. Several human interventional studies have been conducted to assess the effects of blueberry intake on cognitive performance; however, the results of clinical trials are inconclusive. Therefore, this systematic review and meta-analysis evaluated the effect of blueberry supplementation on some aspects of cognitive performance and mood parameters using data from clinical trials based on existing evidence. Methods: Relevant studies, published in April 2021, were searched through PubMed/Medline, Scopus, Embase, and Google Scholar. The random effect size was used to estimate the pooled effect size. Heterogeneity between studies was evaluated by the Cochrane Q test and I-squared (I²). To detect the potential source of heterogeneity, a subgroup analysis was conducted. Results: Fourteenrandomized trials were included in the quantitative analysis, and six were pooled for statistical analysis. Blueberry intervention resulted in no significant change in mood state score (WMD = 0.03; 95% CI: -0.80 to 0.87, P = 0.16). Moreover, no significant effect of blueberry intake was shown in attention task reaction time (WMD = -1.50 ms; 95% CI: -24.75 to -21.75, P = 0.9), percentages of attention task accuracy (WMD = 0.85; 95% CI: -2.57 to 0.86, P = 0.3), one-back test accuracy (WMD = 0.03; 95% CI: -0.04 to 0.09, P = 0.4). Significant effect was indicated (WMD = 0.08; 95% CI: 0.02 to 0.13, P = 0.005) in two-back test accuracy. Conclusion: We found a significant effect of blueberry consumption on two-back test accuracy as a cognitive outcome. More high-quality clinical trials according to the challenges mentioned seem to indicate the use of blueberry as a supplement for cognitive and mood health efficiently.