The Effects of Almond Consumption on Inflammatory Biomarkers in Adults: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Abstract

Statement of Significance: This is the most comprehensive meta-analysis of randomized clinical trials examining the effects of almond consumption on inflammatory biomarkers. Almonds might have beneficial effects on CRP and IL-6 concentrations. Conflicting findings have been reported regarding the effects of almond consumption on inflammatory markers. This study aimed to summarize the current literature to determine whether almonds can affect inflammatory markers. A systematic search was carried out in PubMed, Scopus, and ISI Web of Science up to March 2021. Randomized clinical trials that compared almond with no almond consumption were included. The outcomes of interest were changes in circulating C-reactive protein (CRP), IL-6, TNF-alpha, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) concentrations. The random-effects model was used to find the mean differences. In total, 18 trials with 847 participants were eligible for the current analysis. Participants' ages ranged from 26.3 to 69.6 y. Combining 16 studies, almond consumption significantly reduced serum concentrations of CRP weighted mean difference (WMD): -0.25 mg/L; 95% CI: -0.43, -0.06 mg/L; I-2 = 0.0%; P-heterogeneity = 0.633. However, the beneficial effect of almond intake only occurred at doses <60 g/d. Pooling 11 effect sizes, almond interventions significantly decreased circulating IL-6 concentrations (WMD: -0.11 pg/mL; 95% CI: -0.21, -0.01 pg/mL; I-2 = 19.9%; P-heterogeneity = 0.254). In subgroup analyses, effects on CRP and IL-6 were nonsignificant in unhealthy participants or those with obesity. In addition, almond consumption had no significant effect on TNF-alpha (WMD: -0.05 pg/mL; 95% CI: -0.11, 0.01 pg/mL; I-2 = 0.0%; P-heterogeneity = 0.893; n = 6), ICAM-1 (WMD: 6.39 ng/mL; 95% CI: -9.44, 22.22 ng/mL; I-2 = 66.6%; P-heterogeneity = 0.006; n = 7), or VCAM-1 (WMD: -8.31 ng/mL; 95% CI: -35.32, 18.71 ng/mL; I-2 = 58.8%; P-heterogeneity = 0.033; n = 6). In conclusion, almond consumption beneficially affects CRP and IL-6 concentrations in adults. However, it has no beneficial effect on TNF-alpha, ICAM-1, or VCAM-1. More trials are needed to determine the effects of almonds on inflammation.