Inulin and Oligofructose as Dietary Fiber: A Review of the Evidence

• Published in: Critical reviews in food science and nutrition Vol. 41; no. 5; pp. 353 - 362
• Main Authors: Flamm, Gary, Glinsmann, Walter, Kritchevsky, David, Prosky, Leon, Roberfroid, Marcel
• Format: Journal Article
• Language: English
• Published: Colchester TAYLOR & FRANCIS 01-09-2001; Taylor & Francis
• Subjects: Animals; Biological and medical sciences; Carbohydrates; Colon - metabolism; Dietary Fiber - classification; Dietary Fiber - metabolism; Digestive System Physiological Phenomena; Fatty Acids, Volatile - biosynthesis; Fermentation; Food industries; Fundamental and applied biological sciences. Psychology; General aspects; Humans; Inulin - chemistry; Inulin - metabolism; Metabolisms and neurohumoral controls; Methods of analysis, processing and quality control, regulation, standards; Nutritive Value; Oligosaccharides - chemistry; Oligosaccharides - metabolism; Safety; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Nutritive value; Storage carbohydrate; Foodstuff; Review; Oligomer; Metabolism; Oligofructose; Food intake; Fructosan; Inulin; Plant origin; Chemical composition; Dietary fiber
• ISSN: 1040-8398; 1549-7852
• DOI: 10.1080/20014091091841

The authors express their appreciation to Dr. Barbara Schneeman, University of California, for her review of this manuscript and the opportunity for discussion of key points of the manuscript.
Referee: Dr. Joanne Slavin, Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenues, St. Paul, MN 5108
This critical review article examines the composition and source of inulin and oligofructose, the physiological effects of their consumption, and how these materials relate to the concept of dietary fiber. Inulin and oligofructose are fructans extracted on a commercial basis from the chicory root. Inulin has been defined as a polydisperse carbohydrate material consisting mainly, if not exclusively, of beta (2-1) fructosyl-fructose links ranging from 2 to 60 units long. Native chicory inulin has an average degree of polymerization (DP) of 10 to 20, whereas oligofructose contains chains of DP 2 to 10, with an average DP of 4.
While a universally accepted definition for dietary fiber does not exist, it is generally agreed that this term includes saccharides (+lignin) that are not hydrolyzed or absorbed in the upper part of the gastrointestinal tract. These materials reach the colon, where they may be totally fermented, partially fermented, or remain unfermented. In addition, fibers contribute to fecal bulking.
Inulin and oligofructose are not digested in the upper part of the gastrointestinal tract or are they absorbed and metabolized in the glycolytic pathway, or directly stored as glycogen like 'sugars' or starches. None of the molecules of fructose and glucose that form inulin and oligofructose appear in the portal blood. These materials are quantitatively fermented by the micro flora of the colon; further, it has been demonstrated that this fermentation leads to the selective stimulation of the growth of the bifidobacteria population.
After reviewing their chemistry, origin, and physiological effects, it is the opinion of the authors that inulin and oligofructose are dietary fiber. They share the basic common characteristics of dietary fibers, that is, saccharides of plant origin, resistance to digestion and absorption in the small intestine, and fermentation in the colon to produce short-chain fatty acids that are absorbed and metabolized in various parts of the body. Moreover, this fermentation induces a bulking effect.