Inulin's Health Effects and Mechanisms of Action in Human Metabolism

Inulin is a plant polysaccharide that is used by a wide variety of plants as an energy store. Structurally, it consists of d-fructofuranose units, linked by β (2→1) bonds, usually with a glucose moiety attached to the end by an α (1→2) bond. Inulin is not digestible by human gut enzymes, but it can be digested by some bacteria of the human microbiota, acting as a prebiotic. Due to this condition, during the last years, different studies have been conducted focused on the potential application of inulin as a food ingredient with health-promoting activities against metabolic syndrome diseases. However, the specific effects and mechanisms of action of inulin are still unclear.
Here, we present a bibliographic review of human intervention studies evaluating the effect of inulin supplementation on metabolic parameters to gather evidence on its potential benefits and to describe its mechanisms of action. The study includes studies published in PubMed during the last years.
At the microbiota level, the main effect produced by inulin is the selective favouring of beneficial species in the colon, especially those belonging to the genera Bifidobacterium and Anaerostipes, which have been found to be associated with improved insulin sensitivity, glycemic levels, and anthropometric parameters. In addition, it has been seen that, by competitive exclusion, pathogenic species, such as those of the Clostridium genus, are negatively affected.
On the other hand, inulin fermentation produces short-chain fatty acids, which positively affect different metabolic parameters. They improve glucose metabolism and decrease hepatic lipogenesis, improve intestinal barrier functions, reduce inflammation, modulate immune activity, and improve anthropometric parameters such as weight or BMI.
In conclusion, the scientific evidence analysed suggests that inulin intake produces positive health effects through the improvement in the intestinal microbiota and through the metabolites produced by its fermentation.