Inulin is a fructan carbohydrate (i.e., a chain of fructose molecules) and soluble dietary fiber found naturally in some plants as a form of energy storage. While inulin can be taken as a supplement, it can also be consumed as part of the diet with foods such as Jerusalem artichokes, chicory, asparagus, garlic, onions, wheat, and bananas.[1] Structurally, inulin is usually composed of a straight chain of fructose sugars that are connected by a type of bond (a β-(2,1)-glycosidic bond) that is resistant to human digestive enzymes.[2] Because of this, inulin travels to the large intestine largely undigested and acts as a food source for microbes of the gut microbiome — primarily via bacterial fermentation. This process leads to the production of compounds capable of influencing human health — such as short-chain fatty acid (SCFAs), while also stimulating the growth of potentially beneficial bacteria.[3]
Inulin can be categorized based on the length of its fructose chain, which also influences its physiochemical properties (e.g., solubility, fermentation rate).[1] Long-chain inulin generally consists of 10 to 60 fructose units, while short-chain inulin has 2 to 10 fructose units and is referred to as a fructooligosaccharide (FOS) or oligofructose.[1] Together, short- and long-chain inulin are called “inulin-type fructans,” which will be used synonymously with “inulin” on this page.[4]