Fructooligosaccharides (FOSs) are substances that promote the growth of normal intestinal flora. These compounds are present in small amounts in some foods such as onion, wheat, banana, tomato and honey. "Fructooligosaccharides" consist of "glucose" binding to several units (2 to 7 units) of "fructose". They are not digested or absorbed in the small intestine and therefore enter the colon and consumed by the body's beneficial bacteria. Natural fructo-oligosaccharides in foods contain 2 to 5 units of "fructose" in their structure (figure below).

Benefits of FOSs:

  • Stimulating the growth of normal intestinal flora
  • Increasing the frequency of disposal of faeces and prevent constipation
  • Increasing absorption of "calcium" and "magnesium"
  • Boosting the immune system.


Bruzzese,E.,Volpicelli,M.,Squeglia,V.,Bruzzese,D.,Salvini,F.,Bisceglia,M.,&Guarino, A. (2009). A formula containing galacto-and fructo-oligosaccharides prevents intestinal and extra-intestinal infections: an observational study. Clinical Nutrition, 28(2), 156-161.

Arslanoglu, S., Moro, G.E., & Boehm, G. (2007). Early supplementation of prebiotic oligosaccharides protects formula-fed infants against infections during the first 6 months of life. The Journal of nutrition, 137(11), 2420-2424.