Prebiotics are non-digestable food ingredients that are of benefit to humans by selectively stimulating the growth and/or the activity of one or more types of bacteria in the colon.
In contrast to probiotics, which introduce exogenous bacteria into the human intestine, prebiotics stimulate the preferential growth of a limited number of bacteria already existing in the healthy intestine. Because of their structure, prebiotics are not digested in the upper gastrointestinal tract. They act as soluble fibres and are digested in the colon enhancing microbial activity and stimulating the growth of lactobacilli and bifidobacteria.
A large intake of prebiotics may encourage the formation of gas, flatulence and intestinal discomfort.
The main dairy products enriched with prebiotics are yoghurts and yoghurt drinks, but various spreads, fresh cheeses and milk are also on the market.
The main prebiotics added to europen foods are inulin and various types of fructooligosaccharides. Both of these are found in varying quantity naturally in garlic, artichokes, chicory and onions.
It still remains debatable if prebiotics can boost the immune system of the intestine.