Inulin
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Inulins are a group of naturally occurring
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...
s produced by many types of
plants Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...
, industrially most often extracted from
chicory Common chicory ('' Cichorium intybus'') is a somewhat woody, perennial herbaceous plant of the family Asteraceae, usually with bright blue flowers, rarely white or pink. Native to the Old World, it has been introduced to North America and Austra ...
. The inulins belong to a class of
dietary fiber Dietary fiber (in British English fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by the ...
s known as
fructan A fructan is a polymer of fructose molecules. Fructans with a short chain length are known as fructooligosaccharides. Fructans can be found in over 12% of the angiosperms including both monocots and dicots such as agave, artichokes, asparagus, l ...
s. Inulin is used by some plants as a means of storing energy and is typically found in
root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...
s or
rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...
s. Most plants that synthesize and store inulin do not store other forms of carbohydrate such as
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...
. In the United States in 2018, the
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
approved inulin as a dietary fiber ingredient used to improve the
nutrition Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain sufficient n ...
al value of manufactured food products. Using inulin to measure
kidney function Assessment of kidney function occurs in different ways, using the presence of symptoms and signs, as well as measurements using urine tests, blood tests, and medical imaging. Functions of a healthy kidney include maintaining a person's fluid ...
is the "gold standard" for comparison with other means of estimating
glomerular filtration rate Renal functions include maintaining an acid–base balance; regulating fluid balance; regulating sodium, potassium, and other electrolytes; clearing toxins; absorption of glucose, amino acids, and other small molecules; regulation of blood p ...
.


Origin and history

Inulin is a natural storage carbohydrate present in more than 36,000 species of plants, including
agave ''Agave'' (; ; ) is a genus of monocots native to the hot and arid regions of the Americas and the Caribbean, although some ''Agave'' species are also native to tropical areas of North America, such as Mexico. The genus is primarily known for ...
,
wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
,
onion An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onion ...
,
bananas A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", distinguis ...
,
garlic Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus ''Allium''. Its close relatives include the onion, shallot, leek, chive, Allium fistulosum, Welsh onion and Allium chinense, Chinese onion. It is native to South A ...
,
asparagus Asparagus, or garden asparagus, folk name sparrow grass, scientific name ''Asparagus officinalis'', is a perennial flowering plant species in the genus ''Asparagus''. Its young shoots are used as a spring vegetable. It was once classified in ...
,
Jerusalem artichoke The Jerusalem artichoke (''Helianthus tuberosus''), also called sunroot, sunchoke, wild sunflower, topinambur, or earth apple, is a species of sunflower native to central North America. It is cultivated widely across the temperate zone for its ...
, and chicory. For these plants, inulin is used as an energy reserve and for regulating cold resistance. Because it is soluble in water, it is osmotically active. Certain plants can change the
osmotic potential Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane. It is also defined as the measure of the tendency of a solution to take in a pure s ...
of their cells by changing the degree of polymerization of inulin molecules by hydrolysis. By changing osmotic potential without changing the total amount of carbohydrate, plants can withstand cold and drought during winter periods. Inulin was discovered in 1804 by German scientist Valentin Rose. He found “a peculiar substance” from ''
Inula helenium Elecampane (''Inula helenium''), pronounced and also called horse-heal or elfdock, is a widespread plant species in the sunflower family Asteraceae. It is native to Eurasia from Spain to Xinjiang province in western China, and naturalized in ...
'' roots by boiling-water extraction. In the 1920s, Irvine used chemical methods such as methylation to study the molecular structure of inulin, and he designed the isolation method for this new anhydrofructose. During studies of renal tubules in the 1930s, researchers searched for a substance that could serve as a biomarker that is not reabsorbed or secreted after introduction into tubules. Richards introduced inulin because of its high molecular weight and its resistance to enzymes. Inulin is used to determine
glomerular filtration rate Renal functions include maintaining an acid–base balance; regulating fluid balance; regulating sodium, potassium, and other electrolytes; clearing toxins; absorption of glucose, amino acids, and other small molecules; regulation of blood p ...
of the
kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...
s.


Chemical structure and properties

Inulin is a heterogeneous collection of
fructose Fructose, or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galacto ...
polymers. It consists of chain-terminating
glucosyl A glycosyl group is a univalent free radical or substituent structure obtained by removing the hemiacetal hydroxyl group from the cyclic form of a monosaccharide and, by extension, of a lower oligosaccharide. Glycosyl also reacts with inorganic ...
moieties and a repetitive fructosyl moiety, which are linked by β(2,1) bonds. The degree of polymerization (DP) of standard inulin ranges from 2 to 60. After removing the fractions with DP lower than 10 during manufacturing process, the remaining product is high-performance inulin. Some articles considered the fractions with DP lower than 10 as short-chained fructo-oligosaccharides, and only called the longer-chained molecules inulin. Because of the β(2,1) linkages, inulin is not digested by enzymes in the human alimentary system, contributing to its functional properties: reduced calorie value, dietary fiber, and prebiotic effects. Without color and odor, it has little impact on sensory characteristics of food products. Oligofructose has 35% of the sweetness of sucrose, and its sweetening profile is similar to sugar. Standard inulin is slightly sweet, while high-performance inulin is not. Its solubility is higher than the classical fibers. When thoroughly mixed with liquid, inulin forms a gel and a white creamy structure, which is similar to fat. Its three-dimensional gel network, consisting of insoluble submicron crystalline inulin particles, immobilizes a large amount of water, assuring its physical stability. It can also improve the stability of foams and emulsions.


Uses


Harvesting and extraction

Chicory Common chicory ('' Cichorium intybus'') is a somewhat woody, perennial herbaceous plant of the family Asteraceae, usually with bright blue flowers, rarely white or pink. Native to the Old World, it has been introduced to North America and Austra ...
root is the main source of extraction for commercial production of inulin. The extraction process for inulin is similar to obtaining
sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...
from
sugar beet A sugar beet is a plant whose root contains a high concentration of sucrose and which is grown commercially for sugar production. In plant breeding, it is known as the Altissima cultivar group of the common beet (''Beta vulgaris''). Together wi ...
s. After harvest, the chicory roots are sliced and washed, then soaked in a
solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
(hot water or ethanol); the inulin is then isolated, purified, and spray dried. Inulin may also be synthesized from
sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...
.


Processed foods

Inulin received no-objection status as generally recognized as safe (GRAS) from the US 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. 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 Food energy is chemical energy that animals (including humans) derive from their food to sustain their metabolism, including their muscle, muscular activity. Most animals derive most of their energy from aerobic respiration, namely combining the ...
of carbohydrates (starch, sugar). In addition to being a versatile ingredient, inulin provides nutritional advantages by increasing
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
absorption and possibly
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
absorption, while promoting the growth of intestinal
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
. 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 Dietary fiber (in British English fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by the ...
and is sometimes categorized as a prebiotic. Conversely, it is also considered a FODMAP, a class of carbohydrates which are rapidly fermented in the colon producing gas. Although FODMAPs can cause certain digestive discomfort in some people, they produce potentially favorable alterations in the
intestinal flora Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut mi ...
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 Glycaemia, also known as blood sugar level, blood sugar concentration, or blood glucose level is the measure of glucose concentrated in the blood of humans or other animals. Approximately 4 grams of glucose, a simple sugar, is present in the blo ...
, and may potentially have use in managing blood sugar-related illnesses, such as
metabolic syndrome Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). 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 ''Glomerulus'' () is a common term used in anatomy to describe globular structures of entwined vessels, fibers, or neurons. ''Glomerulus'' is the diminutive of the Latin ''glomus'', meaning "ball of yarn". ''Glomerulus'' may refer to: * the filte ...
capillaries into the
Bowman's capsule Bowman's capsule (or the Bowman capsule, capsula glomeruli, or glomerular capsule) is a cup-like sac at the beginning of the tubular component of a nephron in the mammalian kidney that performs the first step in the filtration of blood to form ur ...
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. In the United States, creatinine clearance is more widely used to estimate GFR. Inulin enhances the growth and activities of bacteria or inhibits growth or activities of certain pathogenic bacteria. Research has linked it to several health benefits, such as helping control diabetes, aiding weight loss and improving digestive health. A 2017
systematic review A systematic review is a Literature review, scholarly synthesis of the evidence on a clearly presented topic using critical methods to identify, define and assess research on the topic. A systematic review extracts and interprets data from publ ...
of
clinical trial Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, dietar ...
results showed that dietary supplementation with inulin reduced
biomarker In biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, p ...
s of metabolic syndrome.


Diet and side effects

The side effects of inulin dietary fiber diet, which may occur, usually in sensitive persons, are: * Intestinal discomfort, including flatulence, bloating, stomach noises, belching, and cramping *
Diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin wi ...
*
Inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
- inulin can cause an allergy-related type of inflammation in the gut and lungs * Anaphylactic allergic reaction (rare) – inulin is used for GFR testing, and in some isolated cases has resulted in an allergic reaction, possibly linked to a food allergy response.


Industrial use

Nonhydrolyzed inulin can also be directly converted to
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
in a simultaneous
saccharification In chemistry, saccharification is a term for denoting any chemical change wherein a monosaccharide molecule remains intact after becoming unbound from another saccharide. For example, when a carbohydrate is broken into its component sugar molecul ...
and fermentation process, which may have potential for converting crops high in inulin into ethanol for fuel.


Biochemistry

Inulins are
polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
s composed mainly of fructose units (
fructans A fructan is a polymer of fructose molecules. Fructans with a short chain length are known as fructooligosaccharides. Fructans can be found in over 12% of the angiosperms including both monocots and dicots such as agave, artichokes, asparagus, leek ...
), and typically have a terminal
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
. The fructose units in inulins are joined by a β(2→1)
glycosidic bond A glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group ...
. The molecule is almost exclusively linear, with only a few percent branching. In general, plant inulins contain between 2 and 70 fructose units or sometimes as high as 200, but molecules with less than 10 units are called fructo-oligosaccharides, the simplest being 1-
kestose Kestose is a class of sugars that belongs to a group of fructooligosaccharides. Chemical properties Kestoses are typical fructooligosaccharides, and in its structure, one fructose molecule is combined with sucrose to form a trisaccharide. ...
, which has two fructose units and one glucose unit. Bacterial inulin is more highly branched (more than 15% branching) and contains on the order of tens or hundreds of subunits. Inulins are named in the following manner, where n is the number of fructose residues and py is the abbreviation for pyranosyl: * Inulins ''with'' a terminal glucose are known as ''alpha''-D-glucopyranosyl- eta-D-fructofuranosyln-1)-D-fructofuranosides, abbreviated as GpyFn. * Inulins ''without'' glucose are ''beta''-D-fructopyranosyl- -fructofuranosyln-1)-D-fructofuranosides, abbreviated as FpyFn. Hydrolysis of inulins may yield fructo-oligosaccharides, which are oligomers with a
degree of polymerization The degree of polymerization, or DP, is the number of monomeric units in a macromolecule or polymer or oligomer molecule. For a homopolymer, there is only one type of monomeric unit and the ''number-average'' degree of polymerization is given b ...
(DP) of 10 or less.


Calculation of glomerular filtration rate

Inulin is uniquely treated by nephrons in that it is completely filtered at the
glomerulus ''Glomerulus'' () is a common term used in anatomy to describe globular structures of entwined vessels, fibers, or neurons. ''Glomerulus'' is the diminutive of the Latin ''glomus'', meaning "ball of yarn". ''Glomerulus'' may refer to: * the filter ...
but neither secreted nor reabsorbed by the tubules. This property of inulin allows the clearance of inulin to be used clinically as a highly accurate measure of glomerular filtration rate (GFR) — the rate of plasma from the
afferent arteriole The afferent arterioles are a group of blood vessels that supply the nephrons in many excretory systems. They play an important role in the regulation of blood pressure as a part of the tubuloglomerular feedback mechanism. The afferent arteriole ...
that is filtered into Bowman's capsule measured in ml/min. It is informative to contrast the properties of inulin with those of para-aminohippuric acid (PAH). PAH is partially filtered from plasma at the glomerulus and not reabsorbed by the tubules, in a manner identical to inulin. PAH is different from inulin in that the fraction of PAH that bypasses the glomerulus and enters the nephron's tubular cells (via the
peritubular capillaries In the renal system, peritubular capillaries are tiny blood vessels, supplied by the efferent arteriole, that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron. Peritubular capillaries s ...
) is completely secreted. Renal clearance of PAH is thus useful in calculation of renal plasma flow (RPF), which empirically is (1-
hematocrit The hematocrit () (Ht or HCT), also known by several other names, is the volume percentage (vol%) of red blood cells (RBCs) in blood, measured as part of a blood test. The measurement depends on the number and size of red blood cells. It is norm ...
) times
renal blood flow In the physiology of the kidney, renal blood flow (RBF) is the volume of blood delivered to the kidneys per unit time. In humans, the kidneys together receive roughly 25% of cardiac output, amounting to 1.2 - 1.3 L/min in a 70-kg adult male. It ...
. Of note, the clearance of PAH is reflective only of RPF to portions of the kidney that deal with urine formation, and, thus, underestimates the actual RPF by about 10%. The measurement of GFR by inulin or sinistrin is still considered the
gold standard A gold standard is a monetary system in which the standard economic unit of account is based on a fixed quantity of gold. The gold standard was the basis for the international monetary system from the 1870s to the early 1920s, and from the la ...
. However, it has now been largely replaced by other, simpler measures that are approximations of GFR. These measures, which involve clearance of such substrates as
EDTA Ethylenediaminetetraacetic acid (EDTA) is an aminopolycarboxylic acid with the formula H2N(CH2CO2H)2sub>2. This white, water-soluble solid is widely used to bind to iron (Fe2+/Fe3+) and calcium ions (Ca2+), forming water-soluble complexes eve ...
,
iohexol Iohexol, sold under the trade name Omnipaque among others, is a contrast agent used for X-ray imaging. This includes when visualizing arteries, veins, ventricles of the brain, the urinary system, and joints, as well as during computed tomograp ...
, cystatin C, 125I-
iothalamate Iotalamic acid, sold under the brand name Conray, is an iodine-containing radiocontrast agent. It is available in form of its salts, sodium iotalamate and meglumine iotalamate. It can be given intravenously or intravesically (into the urinary ...
(sodium radioiothalamate), the chromium radioisotope 51Cr (chelated with EDTA), and
creatinine Creatinine (; ) is a breakdown product of creatine phosphate from muscle and protein metabolism. It is released at a constant rate by the body (depending on muscle mass). Biological relevance Serum creatinine (a blood measurement) is an importa ...
, have had their utility confirmed in large cohorts of patients with chronic kidney disease. For both inulin and creatinine, the calculations involve concentrations in the urine and in the serum. However, unlike creatinine, inulin is not naturally present in the body. This is an advantage of inulin (because the amount infused will be known) and a disadvantage (because an infusion is necessary).


Metabolism ''in vivo''

Inulin is indigestible by the human
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s
ptyalin α-Amylase is an enzyme (EC 3.2.1.1; systematic name 4-α-D-glucan glucanohydrolase) that hydrolyses α bonds of large, α-linked polysaccharides, such as starch and glycogen, yielding shorter chains thereof, dextrins, and maltose: :Endo ...
and
amylase An amylase () is an enzyme that catalyses the hydrolysis of starch (Latin ') into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large amounts of ...
, which are adapted to digest starch. As a result, it passes through much of the
digestive system The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...
intact. Only in the colon do bacteria
metabolise Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
inulin, with the release of significant quantities of
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
,
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
, and/or
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
. Inulin-containing foods can be rather gassy, in particular for those unaccustomed to inulin, and these foods should be consumed in moderation at first. Inulin is a soluble fiber, one of three types of dietary fiber including
soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...
,
insoluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...
, and
resistant starch Resistant starch (RS) is starch, including its degradation products, that escapes from digestion in the small intestine of healthy individuals. Resistant starch occurs naturally in foods, but it can also be added as part of dried raw foods, or use ...
. Soluble fiber dissolves in water to form a gelatinous material. Some soluble fibers may help lower blood cholesterol and glucose levels. Because normal
digestion Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intest ...
does not break inulin down into
monosaccharide Monosaccharides (from Greek ''monos'': single, '' sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units (monomers) from which all carbohydrates are built. They are usually colorless, water-solub ...
s, it does not elevate blood sugar levels and may, therefore, be helpful in the management of diabetes. Inulin also stimulates the growth of bacteria in the gut. Inulin passes through the
stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...
and
duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
undigested and is highly available to the gut bacterial flora. This makes it similar to resistant starches and other fermentable carbohydrates. Some traditional diets contain over 20 g per day of inulin or fructo-oligosaccharides. The diet of the prehistoric hunter-forager in the Chihuahuan Desert has been estimated to include 135 g per day of inulin-type fructans. Many foods naturally high in inulin or fructo-oligosaccharides, such as chicory, garlic, and
leek The leek is a vegetable, a cultivar of ''Allium ampeloprasum'', the broadleaf wild leek ( syn. ''Allium porrum''). The edible part of the plant is a bundle of leaf sheaths that is sometimes erroneously called a stem or stalk. The genus ''Alli ...
, have been seen as "stimulants of good health" for centuries. Due to its resistance to digestive enzymes, inulin resists absorption during its transit through the upper gastrointestinal tract. After reaching the large intestine, inulin is converted by colonic bacteria to a gel known as a prebiotic, a food ingredient that is highly nourishing to
gut microflora Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut mi ...
. As of 2013, no regulatory authority had permitted health claims in the marketing of prebiotics as a class. Inulin's health effects had been studied in small clinical trials, which showed that it causes gastrointestinal adverse effects such as bloating and flatulence, does not affect triglyceride levels or development of
fatty liver Fatty liver disease (FLD), also known as hepatic steatosis, is a condition where excess fat builds up in the liver. Often there are no or few symptoms. Occasionally there may be tiredness or pain in the upper right side of the abdomen. Complicat ...
, may help prevent traveler’s diarrhea, and may help increase calcium absorption in adolescents.


Natural sources

Plants that contain high concentrations of inulin include: *
Agave ''Agave'' (; ; ) is a genus of monocots native to the hot and arid regions of the Americas and the Caribbean, although some ''Agave'' species are also native to tropical areas of North America, such as Mexico. The genus is primarily known for ...
(''Agave'' spp.) *
Banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa''. In some countries, bananas used for cooking may be called "plantains", distinguis ...
and
plantain Plantain may refer to: Plants and fruits * Cooking banana, banana cultivars in the genus ''Musa'' whose fruits are generally used in cooking ** True plantains, a group of cultivars of the genus ''Musa'' * ''Plantaginaceae'', a family of flowerin ...
( Musaceae) *
Burdock ''Arctium'' is a genus of biennial plants commonly known as burdock, family Asteraceae. Native to Europe and Asia, several species have been widely introduced worldwide. Burdock's clinging properties, in addition to providing an excellent mecha ...
(''Arctium lappa'') * Camas (''Camassia'' spp.) *
Chicory Common chicory ('' Cichorium intybus'') is a somewhat woody, perennial herbaceous plant of the family Asteraceae, usually with bright blue flowers, rarely white or pink. Native to the Old World, it has been introduced to North America and Austra ...
(''Cichorium intybus'') * Coneflower (''
Echinacea ''Echinacea'' is a genus of herbaceous flowering plants in the daisy family. It has ten species, which are commonly called coneflowers. They are found only in eastern and central North America, where they grow in moist to dry prairies and open ...
'' spp.) * Costus (''Saussurea lappa'') *
Dandelion ''Taraxacum'' () is a large genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus is native to Eurasia and Nor ...
(''Taraxacum officinale'') *
Elecampane Elecampane (''Inula helenium''), pronounced and also called horse-heal or elfdock, is a widespread plant species in the sunflower family Asteraceae. It is native to Eurasia from Spain to Xinjiang province in western China, and naturalized in ...
(''Inula helenium'') *
Garlic Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus ''Allium''. Its close relatives include the onion, shallot, leek, chive, Allium fistulosum, Welsh onion and Allium chinense, Chinese onion. It is native to South A ...
(''Allium sativum'') *
Globe artichoke The globe artichoke (''Cynara cardunculus'' var. ''scolymus'' ),Rottenberg, A., and D. Zohary, 1996: "The wild ancestry of the cultivated artichoke." Genet. Res. Crop Evol. 43, 53–58. also known by the names French artichoke and green articho ...
(''Cynara scolymus'', ''Cynara cardunculus'' var. ''scolymus'') *
Jerusalem artichoke The Jerusalem artichoke (''Helianthus tuberosus''), also called sunroot, sunchoke, wild sunflower, topinambur, or earth apple, is a species of sunflower native to central North America. It is cultivated widely across the temperate zone for its ...
(''Helianthus tuberosus'') *
Jicama ''Pachyrhizus erosus'', commonly known as jícama ( or ; Spanish ''jícama'' ; from Nahuatl ''xīcamatl'', ) Mexican turnip, is the name of a native Mexican vine, although the name most commonly refers to the plant's edible tuberous root. Jícam ...
(''Pachyrhizus erosus'') *
Leopard's bane Leopard's bane or leopard's-bane may refer to: *'' Aconitum'', also known as aconite, monkshood, wolf's bane, women's bane, Devil's helmet or blue rocket, a genus of flowering plants belonging to the buttercup family *''Arnica montana'', also known ...
(''
Arnica montana ''Arnica montana'', also known as wolf's bane, leopard's bane, mountain tobacco and mountain arnica, is a moderately toxic European flowering plant in the daisy family Asteraceae. It is noted for its large yellow flower head. The names "wolf's ...
'') *
Mugwort Mugwort is a common name for several species of aromatic flowering plants in the genus ''Artemisia.'' In Europe, mugwort most often refers to the species '' Artemisia vulgaris'', or common mugwort. In East Asia the species '' Artemisia argyi'' i ...
root ('' Artemisia vulgaris'') *
Onion An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onion ...
(''Allium cepa'') *
Wild yam Wild yam is a common name for several plants and may refer to: * '' Dioscorea dregeana'', native to southern Africa * ''Dioscorea villosa ''Dioscorea villosa'' is a species of twining tuberous vine which is native to eastern North America. It is ...
('' Dioscorea'' spp.) * ''
Yacón The yacón (''Smallanthus sonchifolius'') is a species of perennial daisy traditionally grown in the northern and central Andes from Colombia to northern Argentina for its crisp, sweet-tasting, tuberous roots. Their texture and flavour are very s ...
'' (''Smallanthus sonchifolius'')


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