- Fructooligosaccharides (FOS), sometimes called oligofructose, belong to the group of prebiotics or prebiotic fibres.
- FOS is of vegetable origin and derived from chicory roots (high concentration of inulin). FOS are very similar but not identical to inulin: they differ in their chemical structures. Fructooligosaccharide chains of molecules are shorter than inulin chains. Chemical structure: chain of fructose units with a terminal glucose unit.
- Prebiotics or prebiotic fibres are typically oligosaccharides such as FOS (and GOS = galactooligosaccharides); they are natural, soluble and fermentable fibres.
- Fermentable fibres (such as GOS and FOS) may provide a number of health benefits by altering the composition of the intestinal flora (bacteria that live in the gut). They are non-digestible (but fermentable) fibres that beneficially affect growth and function of the ‘good’ bacteria bifidobacteria and lactobacilli.
- Increased growth of bifidobacteria and lactobacilli is considered beneficial to human health.
- Changes are more apparent in bifidobacteria than in lactobacilli: more bifidobacteria usually reside in the human colon than lactobacilli, showing a preference for oligosaccharides.
- Caloric value of dietary fibre (e.g. fermentable fibres as GOS and FOS): 2 kcal (8 kJ) per gram (EC Directive 2008/100/EC).
- Human milk contains diverse soluble oligosaccharides (human milk oligosaccharides – HMOS). Colostrum (first milk) contains about 20–25 g/L of HMOS. As milk production matures, HMOS concentrations decline to 5–20 g/L.
- Prebiotic oligosaccharides, such as GOS and FOS, are often added to formulas for infants and children.
- name of the term : Fructooligosaccharides
Main natural sources
- Examples include: onion, chicory root, garlic, asparagus, banana, Jerusalem artichoke, leeks and grains such as wheat and barley.
- FOS can be commercially manufactured from chicory roots (inulin).
Mechanism of action.
- In the gastrointestinal tract, GOS and/or FOS resist hydrolysis (breakdown) by enzymes and, absorption. The oligosaccharides enter into the large intestine (colon).
- In the colon, bifidobacteria and lactobacilli, the good bacterial residents, degrade GOS and FOS through fermentation. They use GOS and FOS for their own growth.
- During this fermentation process, short chain fatty acids (SCFAs) are formed.
- SCFAs lower the colonic pH (more acidic environment), which inhibits growth and survival of pathogens (harmful invaders) and consequently promotes growth of beneficial bacteria (bifidobacteria and lactobacilli).
- SCFAs: acetate, propionate, butyrate – each with unique effects. Butyrate is beneficial for colonic health. It is a source of energy for the colon epithelial cells (cells that line the colon). Butyrate makes the epithelial gut barrier less permeable through increased mucus production and so strengthens its role in disease prevention. Butyrate also promotes normal cell differentiation (specialisation of cells) and proliferation (multiplying).
- Lactate and acetate from bacterial production form a chemical barrier against potential pathogens.
- SCFAs help regulate sodium and water absorption, and can enhance absorption of calcium and other minerals.
- Stimulated growth of bifidobacteria and lactobacilli prevents binding of pathogens to the epithelial cell surface. The more space and nutrients taken by the good ones, the less space and nutrients for the bad ones.
- Stimulated growth of the beneficial bacteria leads to an increased bacterial biomass. This results in an increase in volume and softness of the faeces (good gut motility).
- Growth of the beneficial bacterial leads to an increased bacterial biomass resulting in an increase in volume and softness of the faeces. Prebiotics increase the bacterial mass and the osmotic water-binding capacity in the gut lumen. These actions increase stool weight and frequency, and they also soften the stool, which indirectly contributes to decreased transit time.
Multiple studies show beneficial effects of prebiotics in infants and children.
- Stimulation of growth and/or activity of beneficial bacteria.
- Increased production of SCFA, inhibition of growth and/or activity of pathogenic bacteria. Prebiotics contribute to an increased resistance against infections.
- Improved stool characteristics.
- Improved absorption of particular minerals e.g. iron and calcium.
There is increasing evidence that fermentable dietary fibres (prebiotics) can modulate various properties of the immune system (by stimulating growth of the beneficial bacteria bifidobacteria and lactobacilli). Further studies are required to understand the different mechanisms.
DRIs (Dietary Reference Intakes) have not been established for fructooligosaccharides (FOS).
- Synonyms : FOS, Fructo-Oligosaccharide