Oligosaccharides [Greek oligo = few; sacchar = sugar] are carbohydrates composed of 3 to 9 monosaccharides.
Picture 1. An oligosaccharide example: raffinose
Examples of Oligosaccharides in Foods
- Arabinoxylan-oligosaccharides (derived from cereal grains)
- Fructo-oligosaccharides (FOS) or oligofructose (Jerusalem artichokes, onions, canned foods)
- Galacto-oligosaccharides (GOS): raffinose, stachyose and verbascose (in beans, peas, lentils, cabbage, whole grains), soybean oligosaccharides in soy, and trans-galactooligosaccharides (TOS),
- Gentio-oligosaccharides (produced from pustulan)
- Gluco-oligosaccharides (produced from sucrose)
- Human milk oligosaccharides (HMO) (human breast milk)
- Isomalto-oligosaccharides or IOS (produced from starch)
- Lactosucrose (produced from lactose and sucrose)
- Maltotriose (produced from starch during digestion, found in liquid glucose, brown rice syrup)
- Mannan-oligosaccharides or MOS (artificially produced)
- Melibiose-derived oligosaccharides
- N-acetylchito-oligosaccharides (derived from chitosan)
- Pectic oligosaccharides (derived from pectin)
- Xylo-oligosaccharides (produced from corncob and birch wood)
Oligosaccharides are often added to commercial foods as sweeteners or fiber.
Digestion, Fermentation, Absorption, Function, Side Effects
Oligosaccharides, except maltotriose, are indigestible, which means humans lack enzymes to break them down in the small intestine, so they reach the large intestine, where beneficial colonic bacteria break them down (ferment) to absorbable nutrients, which provide some energy–about 2 Calories (kilocalories) per gram in average . Certain breakdown products of oligosaccharides–namely short-chain fatty acids (SCFAs)–may have beneficial effect on large intestinal lining.
Most oligosaccharides act as a soluble fiber, which may help prevent constipation. Ingestion of large amount of oligosaccharides can result in abdominal bloating and excessive gas (flatulence).
Oligosaccharides as Prebiotics
Prebiotics are non-digestible nutrients that selectively promote the growth of normal intestinal bacteria that may have beneficial effects on the large intestinal lining. Oligosaccharides currently considered as prebiotics include fructooligosaccharides (FOS) or oligofructose and trans-galactooligosaccharides (TOS) .