Whole grain diet reduces systemic inflammation: A meta-analysis of 9 randomized trials

BACKGROUNDS: Observational studies had suggested an inverse association between whole grain consumption and concentration of inflammatory markers, but evidence from interventional studies was inconsistent. Therefore, we conducted a meta-analysis of randomized trials to have a better understanding of this issue. METHODS: This study has been registered in PROSPERO (ID: CRD42018096533). We searched PubMed, Web of Science, Embase, Medline, and Cochrane Library for articles focusing on the topic from inception to 1 January, 2018. Summary standardized mean difference (SMD) and 95% confidence interval (CI) were calculated by using either random effect model or fixed effect model according to the heterogeneity of included studies. Subgroup analysis was also performed. RESULTS: Totally 9 randomized trials included 838 participants were identified. In a pooled analysis of all studies, consumption of whole grains had an inverse association with inflammatory markers (SMD 0.16, 95% CI, 0.02–0.30), including C-reactive protein (CRP), Interleukin-6 (IL-6), Tumor necrosis factor-α (TNF-α), Interleukin-1β (IL-1β). Specific analyses for CRP and IL-6 yielded that whole grain diet was related with a significant decrease in the concentration of CRP (SMD 0.29, 95% CI, 0.08–0.50) and IL-6 (SMD 0.19, 95% CI, 0.03–0.36). CONCLUSIONS: The evidence suggested that citizens could benefit from increased whole grain intake for reducing systemic inflammation. Further well-designed studies are required to investigate the mechanism under the appearance.