Effects of Dietary Patterns on Biomarkers of Inflammation and Immune Responses: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Altered immune cell phenotype and chronic inflammation are key features shared by various chronic diseases. Evidence from nutritional interventions aimed at alleviating inflammation could be a promising approach for the prevention of adverse health outcomes. We therefore aimed to conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) to summarize the recent evidence on the effects of dietary patterns on inflammatory and immune-related biomarkers in humans. PubMed, Medline, and Web of Science databases were searched for publications up to October 2020. In total, 22 RCTs were included in the meta-analysis conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The Mediterranean diet appeared as the dietary pattern that showed the most prominent reductions of inflammatory biomarkers such as IL-6 [mean difference (MD): -1.07 pg/mL (95% CI: -1.94, -0.20); I2: 96%], IL-1β [MD: -0.46 pg/mL (95% CI: -0.66, -0.25); I2: 0%], and C-reactive protein [MD: -1.00 mg/L (95% CI: -2.02, 0.01); I2: 100%]. No substantial effects were observed for the additional dietary patterns studied in intervention research, including the Dietary Adherence to Stop Hypertension diet, and the vegetarian or vegan diets. Future large-scale multifactorial intervention studies are warranted to allow direct comparison of various dietary patterns in relation to a range of biomarkers reflecting multiple inflammatory and immune-related pathways.