Abstract
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.
Highlights
IntroductionMetabolic impairment is characterized by an imbalance of homeostasis of the human body in favour of increased visceral fat, dyslipidaemia, compromised blood pressure and Antioxidants 2022, 11, 403
Of the remaining 35 publications left for full-text reading, 27 were excluded due to the following reasons: (i) unclear dietary regimens or not quantifiable Brazil nut intervention, (ii) data overlapping with another study, (iii) lack of randomization, (iv) investigating the effect of a single administration, (v) in vivo study design, and (vi) lack of placebo/control group
Five studies used as an intervention Brazil nuts [17,19,20,21,22], two used granulated Brazil nuts [23,24] and one used Brazil nut flour [18]
Summary
Metabolic impairment is characterized by an imbalance of homeostasis of the human body in favour of increased visceral fat, dyslipidaemia, compromised blood pressure and Antioxidants 2022, 11, 403. The human body is equipped with an antioxidant system to counteract such processes, but environmental factors, such as nutrient intake, seem to play a key role in enhancing the natural defences of the organism [4,5]. Selenium is an essential micronutrient that functions as a component of many selenoproteins in antioxidant and redox reactions. Selenium is necessary for the functioning of glutathione peroxidase (GPx), which is an antioxidant enzyme that catalyses hydrogen peroxide and lipid hydroperoxide through glutathione metabolism [6]. While GPx protects membrane lipids and other cellular and extracellular components from oxidative damage, selenium has been hypothesized to exert anti-atherogenic effects by lowering oxidative stress in the endothelium
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