Inulin
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Inulins are a group of naturally occurring oligosaccharides (several simple sugars linked together) produced by many types of plants. They belong to a class of carbohydrates known as fructans.
Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes. Most plants which synthesise and store inulin do not store other materials such as starch.
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Biochemistry
Inulins are mainly comprised of fructose units and typically have a terminal glucose. The fructose units in inulins are joined by a beta-(2-1) glycosidic link. Plant inulins generally contain between 2 to 140 fructose units. The simplest type of inulin is 1-kestose is which has 2 fructose units and 1 glucose unit.
Inulins with a terminal glucose are known as alpha-D-glucopyranosyl-[beta-D-fructofuranosyl](n-1)-D-fructofuranosides, abbreviated as GpyFn. Inulins without glucose are beta-D-fructopyranosyl-[D-fructofuranosyl](n-1)-D-fructofuranosides, abbreviated as FpyFn where n is the number of fructose residues and py is the abbreviation for pyranosyl.
Uses and health benefits
People have used plants containing inulin to help relieve diabetes mellitus – a condition characterised by hyperglycemia and/or hyperinsulinemia.
Inulin is indigestible by human enzymes ptyalin and amylase, which are designed to digest starch. As a result, inulin passes through much of the digestive system intact. It is only in the colon that bacteria metabolise inulin, with the release of significant quantities of carbon dioxide and/or methane. Inulin-containing foods are therefore notoriously gassy and not recommended for the socially sensitive.
Inulin is not broken down into simple sugars (monosaccharides) by normal digestion, so it does not elevate blood sugar levels, hence, helping diabetics regulate blood sugar levels. Inulin is, however, not chemically related to insulin; the similarities in name do not relate to any similarity in form or function.
Inulin is also a highly effective prebiotic, stimulating the growth of beneficial probiotic bacteria in the gut. As mentioned, inulin passes through the stomach and duodenum undigested, it is highly available to the gut bacterial flora. This contrasts with proprietary probiotic formulations based on yogurt or milk in which the bacteria have to survive very challenging conditions through the gastrointestinal tract before they are able to colonize the gut.
Sources of inulin
Plants that contain high concentrations of inulin includes:
- Dandelion (Taraxacum officinale)
- Wild Yam (Dioscorea sp.)
- Jerusalem artichokes (Helianthus tuberosus).
Other useful information
Inulin, as it is neither secreted nor reabsorbed in the kidney, was historically used in a important medical test of renal function, specifically a measure of glomerular filtration rate, now largely measured by the creatinine clearance test. The inulin clearance test was performed by injecting inulin, waiting for it to be distributed, and then measuring plasma and urine inulin concentrations.de:Inulin fr:Inuline nl:Inuline