Strict vegetarian diet improves the risk factors associated with metabolic diseases by modulating gut microbiota and reducing intestinal inflammation

Abstract

Low-grade inflammation of the intestine results in metabolic dysfunction, in which dysbiosis of the gut microbiota is intimately involved. Dietary fibre induces prebiotic effects that may restore imbalances in the gut microbiota; however, no clinical trials have been reported in patients with metabolic diseases. Here, six obese subjects with type 2 diabetes and/or hypertension were assigned to a strict vegetarian diet (SVD) for 1 month, and blood biomarkers of glucose and lipid metabolisms, faecal microbiota using 454-pyrosequencing of 16S ribosomal RNA genes, faecal lipocalin-2 and short-chain fatty acids were monitored. An SVD reduced body weight and the concentrations of triglycerides, total cholesterol, low-density lipoprotein cholesterol and haemoglobin A1c, and improved fasting glucose and postprandial glucose levels. An SVD reduced the Firmicutes-to-Bacteroidetes ratio in the gut microbiota, but did not alter enterotypes. An SVD led to a decrease in the pathobionts such as the Enterobacteriaceae and an increase in commensal microbes such as Bacteroides fragilis and Clostridium species belonging to clusters XIVa and IV, resulting in reduced intestinal lipocalin-2 and short-chain fatty acids levels. This study underscores the benefits of dietary fibre for improving the risk factors of metabolic diseases and shows that increased fibre intake reduces gut inflammation by changing the gut microbiota.

Microbial Enterotypes, Inferred by the Prevotella-to-Bacteroides Ratio, Remained Stable during a 6-Month Randomized Controlled Diet Intervention with the New Nordic Diet

“…Even though diet is well known to influence our gut microbiota (9,33), substantial changes in the diet might be needed in order to shift P/B groups (enterotypes). This is supported by a recent study which showed that even a diet shift to a strict vegetarian diet for 1 month did not result in a change of enterotypes (40). Stratification of subjects based on P/B ratio is expected to facilitate the detection of changes not seen when looking at all subjects collectively; however, in the present case, we did not find any significant differences between the lowand high-P/B groups with respect to their response to the dietary interventions after correcting for multiple testing.…”

The Prevention and Treatment of Type 2 Diabetes Mellitus with a Plant-Based Diet

“…Lipocalin-2 is also an inflammatory marker [130]. This study underscores the benefits of soluble dietary fiber in the treatment of metabolic diseases, and shows that increased soluble fiber intake reduces gut inflammation by altering the gut microbiota [129]. The study also showed reduced body weight and concentrations of triglycerides, total cholesterol, low-density lipoprotein cholesterol and hemoglobin A1c, and improved fasting glucose and postprandial glucose levels.…”

“…The vegetarian diet reduced the Firmicutes to Bacteroidetes ratio in the gut microbiota. There was also notably a decrease in the pathobionts such as the Enterobacteriaceae, and an increase in commensal microbes such as Bacteroides fragilis and Clostridium species belonging to clusters XIVa and IV, resulting in reduced intestinal lipocalin-2 levels [129]. Reduced Lipocalin-2 levels are associated with increased insulin sensitivity [130].…”

High-level adherence to a Mediterranean diet beneficially impacts the gut microbiota and associated metabolome

“…In addition, several studies have shown an association between consumption of fibre, fruit and vegetables and increased microbial richness, at either taxonomic or gene level 12–14. It is well established that a sudden diet modification can promptly cause a change in the gut microbiome,11 15 16 although such changes are apparently not sufficiently large or enduring to cause individuals to switch between enterotypes 11 17…”