Inulin is a soluble fiber and fructo-oligosaccharide (FOS) that functions as a prebiotic to promote digestive health by stimulating beneficial bacteria in the gut. New chicory-derived Inulin powder from Swanson Ultra is suitable for adding to many of your favorite foods as a thickening agent and sweetener.nulin is a soluble fiber and fructo-oligosaccharide (FOS) that functions as a prebiotic to promote digestive health by stimulating beneficial bacteria in the gut. New chicory-derived Inulin powder from Swanson Ultra is suitable for adding to many of your favorite foods as a thickening agent and sweetener.