Fructooligosaccharides: What are they? Why should you take them?

Fructooligosaccharides: a specific type of fibre

Also known as oligofructose, fructooligosaccharides are primarily classified as a source of dietary fibre.

Exclusive to the plant kingdom, they are largely composed of complex carbohydrates (polysaccharides) the chemical structure of which impedes activation of digestive enzymes. As a result, they are neither hydrolyzed (metabolised) nor absorbed by the body (1).

Although dietary fibre has no nutritional value, it works in various ways to help regulate digestive balance. There are two forms, each with its own specific properties (2):

• soluble fibre, which dissolves in water, lines the gut walls with a viscous gel which causes the stomach to empty more slowly and effectively produces a feeling of prolonged fullness (3). Very gentle on the gut, this kind of fibre includes types of gum, mucilage, and pectin, as well as the subject of this article, FOS.
• insoluble fibre, which does not dissolve in water, bulks out stools by increasing their volume and acts mechanically to facilitate the mechanism of defecation. However, it’s thought to be more irritating to sensitive guts (4). This kind of fibre includes cellulose, hemicellulose and lignin.

Some types of fibre, though not all, are also fermented in the large intestine. In fact, the way they interact with gut flora (the microbiota) is attracting significant interest among the scientific community (5).

With its complementary and versatile nature, dietary fibre has a direct effect in helping to maintain good general health (6). A daily intake of 25g-30g is thus recommended by one European health safety agency (7), though dietary behavior studies suggest many Europeans (French, Danes, Italians and Czechs) actually consume less than 20g a day (8).

What’s specific about FOS?

Composed of linear chains of fructose units (from 2 to 60) often terminating in a glucose unit, FOS are in some ways similar to sucrose: like table sugar, they actually have a naturally sweet taste, though they have only half the calories (just 2 kcal/g).

Taking on all the advantages of soluble fibre, fructooligosaccharides also offer a prebiotic action (9). As fermentable sugars, they act as a substrate – in other words, nourishment – for bacteria in the large intestine.

This colonic fermentation also results in the release of valuable metabolites, including short-chain fatty acids (SCFAs), the preferred nutrient of colonocytes (the cells lining the walls of the colon) (10). Studies also suggest a link between inadequate production of SCFAs and the onset of gut disorders following antibiotic treatment (11).

How can we boost our intake of fructooligosaccharides?

In their natural state, FOS are found in various plant foods such as wheat, barley, artichokes, bananas, chicory, asparagus, garlic and onion (12). It therefore makes sense to include these foods in your diet on a regular basis.

If, however, your diet is normally low in fibre (with few fruits and vegetables, whole grains and pulses), we’d recommend adding it gradually in order to gauge your particular tolerance threshold.

Too much dietary fibre (or consumption by someone not used to it) can lead to mild digestive discomfort caused by excessive fermentation. Typically, this manifests in bloating, flatulence or nausea (13). In such cases, a slight reduction in your daily fibre intake should be enough to restore optimal gut comfort, before you once again start to gradually increase your intake.

It’s worth knowing that FOS can also be synthesised from cane sugar or beet sugar, via enzymatic fermentation by a particular microscopic fungus called Aspergillus niger. Indeed, it’s this innovative bioconversion which has made it possible to develop FOS supplements.

To boost your intake of FOS, always opt for a fructooligosaccharide supplement based on the strictest quality system (such as Fructooligosaccharides, obtained from sugar beet and produced by the French company Tereos without using GMO) (13-14).