Fructo-oligosaccharides (FOS) also known as oligofructose or oligofructan, are oligosaccharide fructans that are used as an alternative form of sweeteners. Fructo-oligosaccharides exhibit sweetness levels between 30% and 50% of sugar in commercially prepared syrups. FOS is extracted from fruits and vegetables such as bananas, onions, asparagus, leeks, barley, chicory root, garlic and wheat. Wheat grains and cereals, also contain fructo-oligosaccharides.
Fructo-oligosaccharides have been a popular dietary supplement in Japan for many years and are 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 health. It is often considered as a suitable supplement for the prevention of yeast infections too.
Much research into FOS has found, together with inulin, that it can promote calcium absorption within the 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.
FOS seems to be safe when consumed in less than 30 grams per day. They can cause flatulence, intestinal noises, bloating, stomach cramps, and diarrhoea. These effects however, are usually very mild if the dose is less than 10 grams per day.