Effect of Dietary Intervention on Inflammatory and Endothelial Dysfunction Markers in Adults with Metabolic Syndrome: A Systematic Review

Abstract Chronic low-grade inflammation is associated with metabolic syndrome and obesity and is characterized by high serum concentration of inflammatory and endothelial dysfunction markers. Studies have shown that western diets may increase the risk of diabetes mellitus and cardiovascular disease; however, healthy eating interventions have been also shown to improve the inflammatory state and endothelial function. A relationship between mixed diets and markers of inflammation and endothelial dysfunction has been previously suggested, since some foods have antioxidant and anti-inflammatory activity. Therefore, we conducted a systematic review of randomized clinical trials of parallel-group or crossover design studies published in the English language that evaluated the effects of dietary interventions on inflammatory and endothelial dysfunction markers in adults with metabolic syndrome. The literature search included electronic databases, manual search, and peer-reviewed articles published from 2005 to 2015. Fourteen studies, with a total of 1470 participants, met the inclusion criteria. Dietary interventions ranged from 2 to 52 weeks. Half of the studies reported a positive effect of dietary interventions on inflammatory markers, being C-reactive protein the one most frequently quantified. Compared to control groups, diets rich in polyunsaturated fatty acids reduced serum CRP levels; Mediterranean diets enriched in olive oil and nuts reduced serum IL-6; and a decrease in serum ICAM levels was observed in Mediterranean diet rich in olive oil. Four of the analyzed studies measured serum TNF-alpha levels, which did not exhibit a significant variation among groups.