Fructooligosaccharides (FOS) also sometimes called oligofructose or oligofructan, are

oligosaccharide An oligosaccharide (; ) is a carbohydrate, saccharide polymer containing a small number (typically three to ten) of monosaccharides (simple sugars). Oligosaccharides can have many functions including Cell–cell recognition, cell recognition and ce ...

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 dicotyledon, dicots such as agave, artichokes, a ...

s, used as an alternative

sweetener A sweetener is a substance added to food or drink to impart the flavor of sweetness, either because it contains a type of sugar, or because it contains a sweet-tasting sugar substitute. Various natural non-sugar sweeteners (NSS) and artificial s ...

. FOS exhibits sweetness levels between 30 and 50 percent of

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 Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...

in commercially prepared

syrup In cooking, syrup (less commonly sirup; from ; , beverage, wine and ) is a condiment that is a thick, viscous liquid consisting primarily of a Solution (chemistry), solution of sugar in water, containing a large amount of dissolved sugars but ...

s. It occurs naturally, and its commercial use emerged in the 1980s in response to demand for healthier and calorie-reduced foods.

Chemistry

Two different classes of fructooligosaccharide (FOS) mixtures are produced commercially, based on

inulin 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 ...

degradation or transfructosylation processes. FOS can be produced by degradation of inulin, or polyfructose, a polymer of D-fructose residues linked by β(2→1) bonds with a terminal α(1→2) linked D-glucose. The degree of polymerization of inulin ranges from 10 to 60. Inulin can be degraded enzymatically or chemically to a mixture of oligosaccharides with the general structure Glu–Fru_n (abbrev. GF_n) and Fru_m (F_m), with n and m ranging from 1 to 7. This process also occurs to some extent in nature, and these oligosaccharides may be found in a large number of plants, especially in

Jerusalem artichoke The Jerusalem artichoke (''Helianthus tuberosus''), also called sunroot, sunchoke, wild sunflower, topinambur, or earth apple, is a species of Helianthus, sunflower native to central North America. It is cultivated widely across the temperate z ...

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 Europe, it has been introduced to the Americas and Australia. M ...

and the

blue agave ''Agave tequilana'', commonly called blue Weber agave () or tequila agave, is an agave plant that is an important economic product of Jalisco state of Mexico, due to its role as the base ingredient of tequila. The high production of agavins (bran ...

plant. The main components of commercial products are

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. In ...

(GF₂), nystose (GF₃), fructosylnystose (GF₄), bifurcose (GF₃), inulobiose (F₂), inulotriose (F₃), and inulotetraose (F₄). The second class of FOS is prepared by the transfructosylation action of a β-fructosidase of ''

Aspergillus niger ''Aspergillus niger'' is a mold classified within the ''Nigri'' section of the ''Aspergillus'' genus. The ''Aspergillus'' genus consists of common molds found throughout the environment within soil and water, on vegetation, in fecal matter, on de ...

'' or '' Aspergillus '' on

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 ...

. The resulting mixture has the general formula of GF_n, with n ranging from 1 to 5. Contrary to the inulin-derived FOS, not only is there β(1→2) binding but other linkages do occur, however, in limited numbers. Because of the configuration of their

glycosidic bond A glycosidic bond or glycosidic linkage is a type of ether 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 o ...

s, fructooligosaccharides resist

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

saliva Saliva (commonly referred as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which ...

ry and intestinal

digestive enzyme Digestive enzymes take part in the chemical process of digestion, which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes ...

s. In the colon they are fermented by

anaerobic bacteria An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenat ...

. In other words, they have a lower caloric value, while contributing to the

dietary fiber Dietary fiber (fibre in English in the Commonwealth of Nations, Commonwealth English) 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 co ...

fraction of the diet. Fructooligosaccharides are more

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 solubi ...

than inulins and are, therefore, sometimes used as an additive to

yogurt Yogurt (; , from , ; also spelled yoghurt, yogourt or yoghourt) is a food produced by bacterial Fermentation (food), fermentation of milk. Fermentation of sugars in the milk by these bacteria produces lactic acid, which acts on milk protein to ...

and other (

dairy A dairy is a place where milk is stored and where butter, cheese, and other dairy products are made, or a place where those products are sold. It may be a room, a building, or a larger establishment. In the United States, the word may also des ...

) products. Fructooligosaccharides are used specially in combination with high-intensity artificial sweeteners, whose sweetness profile and aftertaste it improves.

Food sources

FOS is extracted from the

plant as well as fruits and vegetables such as

banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus '' Musa''. In some countries, cooking bananas are called plantains, distinguishing the ...

onion An onion (''Allium cepa'' , from Latin ), 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 which was classifie ...

root,

garlic Garlic (''Allium sativum'') is a species of bulbous flowering plants in the genus '' Allium''. Its close relatives include the onion, shallot, leek, chives, Welsh onion, and Chinese onion. Garlic is native to central and south Asia, str ...

asparagus Asparagus (''Asparagus officinalis'') is a perennial flowering plant species in the genus ''Asparagus (genus), Asparagus'' native to Eurasia. Widely cultivated as a vegetable crop, its young shoots are used as a spring vegetable. Description ...

jícama ''Pachyrhizus erosus'', commonly known as ''jícama'' ( or ; ; from ) or Mexican turnip, is a native Mesoamerican vine, although the name ''jícama'' most commonly refers to the plant's edible tuberous root. It is in the pea family (Fabaceae ...

, and

leek A leek is a vegetable, a cultivar of ''Allium ampeloprasum'', the broadleaf wild leek (synonym (taxonomy), syn. ''Allium porrum''). The edible part of the plant is a bundle of Leaf sheath, leaf sheaths that is sometimes erroneously called a "s ...

s. Some grains and cereals, such as

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

and

barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

, also contain FOS. The

and its relative

yacón The yacón (''Smallanthus sonchifolius'') is a species of 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 similar t ...

together with the blue agave plant have been found to have the highest concentrations of FOS of cultured plants.

Health benefits

FOS has been a popular sweetener in

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

and

Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...

for many years, even before 1990, when the Japanese government installed a "Functionalized Food Study Committee" of 22 experts to start to regulate "special nutrition foods or

functional food A functional food is a food claimed to have an additional benefit beyond just nutrition (often one related to health promotion or disease prevention) by modifying the horticulture, cultivation of the native food or by food additive, adding ingr ...

s" that contain the categories of fortified foods (e.g., vitamin-fortified wheat flour), and is now becoming increasingly popular in Western cultures for its prebiotic effects. FOS serves as a substrate for microflora in the large intestine, increasing the overall

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...

health. It has also been proposed as a supplement for treating

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...

infections. Several studies have found that FOS and inulin promote calcium absorption in both the animal and the human gut. The intestinal microflora in the lower gut can ferment FOS, which results in a reduced pH. Calcium is more soluble in acid, and, therefore, more of it comes out of food and is available to move from the gut into the bloodstream. In a

randomized controlled trial A randomized controlled trial (or randomized control trial; RCT) is a form of scientific experiment used to control factors not under direct experimental control. Examples of RCTs are clinical trials that compare the effects of drugs, surgical ...

involving 36 twin pairs aged 60 and above, participants were given either a prebiotic (3375 mg

and 3488 mg FOS) or a

placebo A placebo ( ) can be roughly defined as a sham medical treatment. Common placebos include inert tablets (like sugar pills), inert injections (like saline), sham surgery, and other procedures. Placebos are used in randomized clinical trials ...

daily for 12 weeks along with

resistance exercise Strength training, also known as weight training or resistance training, is exercise designed to improve physical strength. It is often associated with the lifting of weights. It can also incorporate techniques such as bodyweight exercises (e ...

and

branched-chain amino acid A branched-chain amino acid (BCAA) is an amino acid having an aliphatic substituent, side-chain with a branch (a central carbon atom bound to three or more carbon atoms). Among the proteinogenic amino acids, there are three BCAAs: leucine, isoleu ...

(BCAA) supplementation. The trial, conducted remotely, showed that the prebiotic supplement led to changes in the

gut microbiome 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 g ...

, specifically increasing

Bifidobacterium ''Bifidobacterium'' is a genus of gram-positive, nonmotile, often branched anaerobic bacteria. They are ubiquitous inhabitants of the gastrointestinal tract though strains have been isolated from the vagina and mouth ('' B. dentium'') of mamma ...

abundance. While there was no significant difference in chair rise time between the prebiotic and placebo groups, the prebiotic did improve

cognition Cognition is the "mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, thought, ...

. The study suggests that simple gut microbiome interventions could enhance

cognitive function Cognitive skills are skills of the mind, as opposed to other types of skills such as motor skills, social skills or life skills. Some examples of cognitive skills are literacy, self-reflection, logical reasoning, abstract thinking, critical th ...

in the elderly. FOS can be considered a small

dietary fibre Dietary fiber (fibre in Commonwealth English) 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 b ...

with (like all types of fibre) low caloric value. The fermentation of FOS results in the production of gases and short chain fatty acids. The latter provide some energy to the body.

Side-effects

All inulin-type prebiotics, including FOS, are generally thought to stimulate the growth of ''

Bifidobacteria ''Bifidobacterium'' is a genus of gram-positive, nonmotile, often branched anaerobic bacteria. They are ubiquitous inhabitants of the gastrointestinal tract though strains have been isolated from the vagina and mouth ('' B. dentium'') of mamma ...

'' species. Bifidobacteria are considered beneficial bacteria. This effect has not been uniformly found in all studies, either for bifidobacteria or for other gut organisms. FOS are also fermented by numerous bacterial species in the intestine, including ''

Klebsiella ''Klebsiella'' is a genus of Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. ''Klebsiella'' is named after German-Swiss microbiologist Edwin Klebs (1834–1913). Carl Friedlander described ' ...

'', ''

E. coli ''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escherichia'' that is commonly foun ...

'' and many ''

Clostridium ''Clostridium'' is a genus of anaerobic, Gram-positive bacteria. Species of ''Clostridium'' inhabit soils and the intestinal tracts of animals, including humans. This genus includes several significant human pathogens, including the causative ...

'' species, which can be pathogenic in the gut. These species are responsible mainly for the gas formation (hydrogen and carbon dioxide), which results after ingestion of FOS. Studies have shown that up to 20 grams/day is well tolerated.

Regulation

US FDA regulation

FOS is classified as

generally recognized as safe Generally recognized as safe (GRAS) is a United States Food and Drug Administration (FDA) designation that a chemical or substance added to food is considered safe by experts under the conditions of its intended use. An ingredient with a GRAS d ...

(GRAS).

NZ FSANZ regulation

The Food Safety Authority warned parents of babies that a major European baby-formula brand made in New Zealand does not comply with local regulations (because it contains fructo-oligosaccharides (FOS)), and urged them to stop using it.Inulin, FOS and GOS assessed in Australia, NZ
/ref>

EU regulation

FOS use has been approved in the European Union; allowing addition of FOS in restricted amounts to baby formula (for babies up to 6 months) and follow-on formula (for babies between 6 and 12 months). Infant and follow-on formula products containing FOS have been sold in the EU since 1999.

Canadian regulations

FOS is currently not approved for use in baby formula.

References

{{carbohydrates Oligosaccharides Prebiotics (nutrition) Sugar substitutes