Inulins are a group of naturally occurring polysaccharides produced by many types of plants, industrially most often extracted from chicory. The inulins belong to a class of dietary fibers 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 that synthesize and store inulin do not store other forms of carbohydrate such as starch. In 2018, the United States Food and Drug Administration approved inulin as a dietary fiber ingredient used to improve the nutritional value of manufactured food products. Using inulin to measure kidney function is the "gold standard" for comparison with other means of estimating glomerular filtration rate.

Harvesting and extraction

Chicory root is the main source of extraction for commercial production of inulin. The extraction process for inulin is similar to obtaining sugar from sugar beets. After harvest, the chicory roots are sliced and washed, then soaked in a solvent (hot water or ethanol);[16] the inulin is then isolated, purified, and spray dried. Inulin may also be synthesized from sucrose.

Processed foods

Inulin received no-objection status as generally recognized as safe (GRAS) from the U.S. Food and Drug Administration (FDA), including long-chain inulin as GRAS. In the early 21st century, the use of inulin in processed foods was due in part to its adaptable characteristics for manufacturing. It is approved by the FDA as an ingredient to enhance the dietary fiber value of manufactured foods.[3] Its flavor ranges from bland to subtly sweet (about 10% of the sweetness of sugar/sucrose). It can be used to replace sugar, fat, and flour. This is advantageous because inulin contains 25–35% of the food energy of carbohydrates (starch, sugar). In addition to being a versatile ingredient, inulin provides nutritional advantages by increasing calcium absorption and possibly magnesium absorption, while promoting the growth of intestinal bacteria. Chicory inulin is reported to increase absorption of calcium in young women with lower calcium absorption and in young men. In terms of nutrition, it is considered a form of soluble fiber and is sometimes categorized as a prebiotic. It is also considered a FODMAP, a class of carbohydrates which are rapidly fermented in the colon producing gas. Although FODMAPs may cause certain digestive discomfort in some people, they produce potentially favorable alterations in the intestinal flora that contribute to maintaining health of the colon.

Due to the body's limited ability to process fructans, inulin has minimal increasing impact on blood sugar, and may potentially have use in managing blood sugar-related illnesses, such as metabolic syndrome.

Medical

Inulin and its analog sinistrin are used to help measure kidney function by determining the glomerular filtration rate (GFR), which is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time.

While inulin is the gold standard for measuring the GFR, it is rarely used in practice due to the expense and difficulty in conducting the test; it requires intravenous (IV) access for the infusion of inulin as well as up to twelve blood samples taken from the patient over the course of four hours. To determine the glomerular filtration rate in humans, a large initial dose of inulin is injected, which is followed by a constant infusion of inulin at a rate which compensates for its loss in the urine, thus maintaining a reasonably constant level in the plasma.: 228  In the United States, creatinine clearance is more widely used to estimate GFR.