Sandwiched in between sugar and the starches are a group of carbohydrates called oligosaccharides, that we never heard much about until recently, and most people probably still have no idea what they are.
Oligosaccharides are carbohydrates which have 3-10 simple sugars linked together, placing them between simple sugars (mon-and disaccharrides) and starches (polysaccharides).
Recent interest has also been drawn to oligosaccharides because of an important characteristic: the human digestive system has a hard time breaking down many of these carbohydrates.
Oligosaccharides are found naturally, at least in small amounts, in many plants. Plants with large amounts of oligosaccharides include chicory root, from which most commercial inulin is extracted, and so-called Jerusalem artichokes. They are also found in onions, leek, garlic, legumes, wheat, barley and asparagus. From food alone, most Americans ingest only about 3 grams naturally each day, while Europeans get up to 10 grams a day.
Although oligosaccharides can be seen as fiber as they share the characteristic of not being easily digested, they are mostly not labeled as fiber.
Almost 90% of the oligosaccharides escape digestion in the small intestine and reaches the colon where it performs a different function: that of a prebiotic.
A prebiotic is a food components that support the growth of certain kinds of bacteria in the colon. At first, it was thought that oligosaccharides were the main prebiotics, but it turns out that resistant starch and fermentable fiber also feeds these bacteria.
Oligosaccharides are gaining attention for their numerous roles in promoting and protecting human health. Researchers have reported beneficial effects on constipation, mineral absorption, lipid metabolism, glucose metabolism and immunomodulation, among others.
Because of the exciting advantages of oligosaccharides for health and the small amounts most people ingest naturally, they are being added to many food and supplement products and include inulin, fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS).
Human breast milk is another source of oligosaccharides; it provides a rich supply of galacto-oligosaccharides (GOS) that has been shown to support a healthy immune system in infants.
While probiotics have achieved much popularity because digestive health depends so much on the amount of beneficial bacteria in the gut, researchers believe that prebiotics are just as important for these bacteria to thrive and this has caused a slow shift of perspective towards prebiotics in recent times.
To enable the continued growth and multiplication, of the gut flora, enough (indigestable) fibers are necessary. These fibers act as food for the bacteria and enable a healthy number of them to be present in the gut and aid digestion.
The major types of prebiotic ingredients are galacto-oligosaccharides (GOS), fructo-oligosaccharides (FOS), inulin, mannan oligosaccharides (MOS) and other natural ingredients that include chicory fructans, xylo-oligosaccharide (XOS), resistant starch prebiotics, etcetera.
In the part below we will shortly describe each type of oligosaccharide
FOS - Fructo-oligosaccharides
Fructo-oligosaccharides (FOS) are soluble fibers that promote gut and overall health through their fermentation by gut flora, to yield important metabolites, including lactic acid and the short chain fatty acids acetate, propionate and butyrate.
These metabolites help to maintain proper pH in the gut, discourage the growth of unfriendly bacteria, reduce the absorption of toxic ammonia and positively affect bone health by increasing the bioavailability of dietary calcium. Moreover, acetate, propionate and butyrate promote the integrity of the intestinal cells lining the colon and promote healthy lipid metabolism.
MOS - Mannan-oligosaccharides
Mannose or mannan-oligosaccharide (MOS) has been shown to improve gastrointestinal health as well as overall health, thus improving wellbeing, energy levels and performance. Most mannose is derived from the cell wall of the yeast, Saccharomyces cerevisiae.
The form present in the cell wall of Saccharomyces cerevisiae is particularly effective at binding pathogens, including those present outside the colon, such as in the bladder, where supplemental D-Mannose acts as a molecular decoy to prevent bacteria from attaching to and infecting bladder cells upon which they can simply be removed when urinating.
Mannose has been found to effectively diminish amounts of Salmonella, E.coli, and Clostridia pathogens.
GOS - Galacto-oligosaccharides
Various studies have shown that Galactooligosaccharides (GOS) selectively stimulate the growth of health-promoting probiotic organisms. With regard to early life, research has demonstrated that the intestinal flora of breast-fed infants differs from that of bottle-fed infants. Breast-fed infants have a higher number of Bifidobacteria, which has been attributed to bifidogenic factors such as GOS.
Bifidobacteria are particularly important for infants since they are the dominant probiotic bacteria in infants, are associated with gastrointestinal health and may be important primers for the immune system.
Later in life, GOS supports a variety of other benefits, some perhaps unexpected. For instance, the natural GOS extracted from peas has been clinically tested for its effect of promoting satiation.
Fermentation of GOS in the colon results in the production of short-chain fatty acids (SCFA), such as propionate, acetate, lactate and butyrate, which are considered to be beneficial to the health of the host. SCFA are a source of nutrients for the intestinal cells and other tissues. The SCFA have the effect of decreasing the pH of the colon.
As humans age, the relative abundance of Bifidobacteria species decreases. Older consumers may benefit significantly in that as GOS supports the growth of Bifidobacteria, promotes regularity and may stimulate calcium absorption.
XOS - Xylo-oligosaccharides
Xylo-oligosaccharides or XOS is a prebiotic fibre that promotes bowel regularity and digestive health. As a prebiotic, XOS just like other oligosaccharides is digested by especially bifidobacteria in the colon that thrive on them, causing the re-establish a healthy balance between “good” vs “bad” bacteria. This improvement in gut ecology is beneficial to human health for a number of reasons; it regulates bowel function to prevent and/or relieve constipation and diarrhea, improves metabolic parameters such as reducing fat production in the liver, increases the excretion of cholesterol in the feces, improves nutrient absorption and improves altered gut microflora in type II diabetics. Furthermore, XOS is considered to be a source of dietary fibre, which has benefits for cardiovascular, metabolic, digestive and cellular health amongst its role in promoting bowel regularity.
XOS is one of many different prebiotics including fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), raffinose and inulin; however, XOS differs from most other prebiotics in a very important way. All prebiotics promote the growth of gut microflora, good and also bad, but XOS selectively promotes the growth of only beneficial microflora, namely bifidobacteria. XOS is considered to be one of the most beneficial prebiotics because it is highly effective at improving the GI ecosystem compared to the other prebiotics.