Effect of Brazil Nuts on Selenium Status, Blood Lipids, and Biomarkers of Oxidative Stress and Inflammation: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Tree nuts, including Brazil nuts, have been hypothesized to impact cardiovascular health through the modulation of oxidative stress and inflammation. Nonetheless, a quantitative analysis of these effects has not been performed. Therefore, the aim of this study was to systematically revise and quantify the effect of Brazil nut intervention on selenium status, blood lipids, and biomarkers of oxidative stress and inflammation using a meta-analytical approach. To meet the goals of this study, a systematic search of PubMed, EMBASE, and Web of Science databases of published randomised clinical trials reporting on dietary interventions with Brazil nuts and their effects on selenium status, blood lipids, and markers of oxidative stress and inflammation was performed. Eight articles were included for systematic review and meta-analysis. Based on the conducted analysis, a significant positive effect of Brazil nuts on selenium blood concentration (SMD = 6.93, 95% CI: 3.99; 9.87) was found. Additionally, a positive effect of Brazil nut intervention on glutathione peroxidase activity (SMD = 0.53, 95% CI: 0.07; 0.99) was observed. However, no significant results were found when considering blood lipid levels, including results for total cholesterol (SMD = −0.22, 95% CI: −0.57; 0.14), HDL cholesterol (SMD = −0.04, 95% CI: −0.28; 0.19) and LDL cholesterol (SMD = −0.15; 95% CI: −0.43; 0.13). In conclusion, the findings from this study suggest that Brazil nut consumption improves selenium status and exerts antioxidant effects, which could be considered a potential pathway for the prevention of metabolic disorders related to altered blood lipid profiles. However, further studies are needed to elucidate the effect of Brazil nuts toward blood lipid profile, also preferably controlling for other biomarkers.