Impact of Different Dietary Fibers in Gastric Emptying Time and Intestinal Transit of Healthy Volunteers

Overview

The digestive process begins in the mouth and follows in the stomach and intestine. In the stomach the food is mixed with the gastric juices forming the chyme. To mix the food with the gastric juice as well as to provide gastric emptying (GE), the movements of the stomach are of great importance. Intestinal transit time is understood of the combination of GE, small intestine transit and colon transit time. The composition of the diet (lipid and protein content) exerts a direct influence on intestinal transit time due to the stimulation of hormone secretion, cholecystokinin and gastrin, respectively, which act to decrease GE velocity. In this context, it is also observed an important influence of dietary fibers on the speed of GE. Despite all knowledge about dietary fibers, information on such compounds still has many controversies. Due to the difficulty of finding compounds that fit into only one specific category (viscous, fermentable or prebiotic) there is difficulty in establishing a concept that best defines what are dietary fibers. The CODEX Alimentarius Commission in 2009 defined dietary fibers as carbohydrate polymers composed of ten or more monomer units of this macronutrient, which are not hydrolyzed by enzymes in the human intestine. Dietary fibers can be classified into insoluble and soluble according to the ability to bind to water molecules and form gels. Soluble fibers, especially those classified as prebiotic, in the intestine are fermented by bacteria giving rise to short chain fatty acids (SCFA). The SCFA stimulates the production and secretion of PYY and GLP-1 are associated with inhibition of gastric motility. Due to the importance of knowing the intestinal transit time, several methods have been developed, but scintigraphy is the gold standard technique for this analysis. Given the above and controversies present in the literature on the dietary fibers, there was a shortage of studies with the objective of evaluating the impact of different dietary fibers in intestinal transit time. This study shows relevant to help elucidate the behavior of different dietary fibers in intestinal transit time, offering data for correct and safe use of dietary fibers in various clinical situations. The hypothesis of this study is that the partially hydrolyzed guar gum delays the time of gastric emptying and intestinal transit, being this effect not observed for fructooligosaccharide