Because FOS is indigestible, it acts as a non-digestible fibre in the diet. This is because the body does not possess the necessary enzymes to break down the FOS as it travels down the digestive tract. When it reaches the large intestine and the colon, the bacteria that are naturally present there start to break down the FOS as the bacteria have the enzymes necessary to do so. Bifido bacteria use FOS and foods that promote the growth of the bifido bacteria are good for health. FOS increases the amount of beneficial bacteria in the lower intestine, and thus there are improvements in the digestion and absorption of nutrients, detoxification and elimination processes, and in the immune system.
FOS may also help to relieve constipation and other gastrointestinal disorders including problems that are related to irritable bowel syndrome, inflammatory bowel disease, and lactose intolerance.