Diets naturally rich in polyphenols and/or long-chain n-3 polyunsaturated fatty acids differently affect microbiota composition in high-cardiometabolic-risk individuals

Aims Gut microbiota significantly impacts human health and is influenced by dietary changes. We evaluated the effects of diets naturally rich in polyphenols (PP) and/or long-chain n-3 polyunsaturated fatty acids (LCn3) on microbiota composition in an ancillary analysis of a randomized controlled trial in individuals at high cardiometabolic risk. Methods Seventy-eight individuals with high waist circumference and at least one additional component of the metabolic syndrome were randomized to an isoenergetic 8-week diet: (a) low LCn3 and PP; (b) high LCn3; (c) high PP; or (d) high LCn3 and PP. Microbiota analysis was performed on feces collected before and after the intervention. DGGE analysis of the predominant bacteria, Eubacterium rectale and Blautia coccoides group ( Lachnospiraceae , EREC), Clostridium leptum ( Ruminococcaceae , CLEPT), Bacteroides spp. , Bifidobacteria, and Lactobacillus group was performed. A quantitative real-time PCR was performed for the same group, additionally including Atopobium cluster ( Coriobatteriaceae ). Before and after the intervention, participants underwent a 75 g OGTT and a high-fat test meal to evaluate glucose and lipid response. Results Adherence to the four diets was optimal. PP significantly increased microbial diversity ( p = 0.006) and CLEPT ( p = 0.015), while it reduced EREC ( p = 0.044). LCn3 significantly increased the numbers of Bifidobacteria ( p = 0.041). Changes in CLEPT numbers correlated with changes in early insulin secretion ( r = 0.263, p = 0.030). Changes in Atopobium numbers correlated with postprandial triglycerides in plasma ( r = 0.266, p = 0.026) and large VLDL ( r = 0.313, p = 0.009), and cholesterol in large VLDL ( r = 0.319, p = 0.008). Conclusions Diets naturally rich in PP or LCn3 influenced gut microbiota composition in individuals at high cardiometabolic risk. These modifications were associated with changes in glucose/lipid metabolism.