Effect of polysaccharide-induced viscosity on the digestion of proteins, fats, and carbohydrates in food: A comprehensive review and future perspectives

Background: Polysaccharides play a crucial role in slowing macronutrient digestion, contributing to satiety, glycemic control, regulating blood sugar levels, and cholesterol management. Their impact on food digestion and absorption is largely mediated by their ability to increase the viscosity of chyme and digesta, affecting the activity of digestive enzymes. Scope and approach: This review examines the effects of polysaccharides on digestive enzymes, focusing on their inhibition of proteolysis, lipolysis, and amylolysis. While other ingredients like gelatin or specific food additives can increase food viscosity, this review specifically emphasizes polysaccharides, particularly soluble fibers. A comprehensive search in Web of Science/ScienceDirect identified 1589 articles published between January 1982 and August 2023. After applying selection criteria, 212 trials from 96 articles that directly examined the influence of polysaccharide viscosity on macronutrient digestibility were included. Key findings and conclusions: The review identifies 38 polysaccharides, including pectin, xanthan, guar gum, carboxymethylcellulose, carrageenan, and konjac glucomannan, known for their viscosity-enhancing properties. These polysaccharides impact nutrient digestion through several mechanisms: they reduce diffusion and mass transfer, impede mixing of digestive components, block enzyme active sites, induce conformational changes, and form aggregates and surface bonds that immobilize substrates. The extent of digestion inhibition is influenced by factors such as polysaccharide concentration, viscosity, and molecular structure, as well as the properties of the substrate, including molecular weight and conformation. The review highlights the need for more accurate modeling of digestive processes and in vitro systems that effectively replicate digestive conditions to better understand the impact of polysaccharides on nutrient digestion and absorption. Future research should explore complex systems, including whole foods and fiber-rich by-products like fruit peels or grain husks containing both soluble and insoluble fiber, to gain deeper insights into how polysaccharides affect into nutrient digestion and absorption in real-world scenarios.