To study the effects of a functional food-based dietary intervention on faecal microbiota and biochemical parameters in patients with type 2 diabetes (T2D).

This placebo-controlled, randomized, double-blind study included 81 patients with T2D divided into two 3-month treatment groups: one following a reduced-energy diet with a dietary portfolio (DP) comprising high-fibre, polyphenol-rich and vegetable-protein functional foods; the other taking a placebo (P). The primary outcome was the effect of the DP on faecal microbiota. Secondary endpoints were biochemical parameters, lipopolysaccharide, branched-chain amino acids, trimethylamine N-oxide, glycosylated haemoglobin (HbA_1c) and free fatty acids (FFAs).

Patients with T2D exhibited intestinal dysbiosis characterized by an increase in Prevotella copri. Dietary intervention with functional foods significantly modified faecal microbiota compared with P by increasing alpha diversity and modifying the abundance of specific bacteria, independently of antidiabetic drugs. There was a decrease in P. copri and increases in Faecalibacterium prausnitzii and Akkermansia muciniphila, two bacterial species known to have anti-inflammatory effects. The DP group also exhibited significant reductions in areas under the curve for glucose, total and LDL cholesterol, FFAs, HbA_1c (P< 0.05), triglycerides and CRP, and an increase in antioxidant activity (P< 0.01) vs. the P group.

Long-term adherence to a high-fibre, polyphenol-enriched and vegetable-protein-based diet provides benefits for the composition of faecal microbiota, and may offer potential therapies for improvement of glycaemic control, dyslipidaemia and inflammation.