Abstract
The intestinal flora plays an important role in stimulating the defence system of the organism. There are indications that children of the industrialised world are underexposed to natural intestinal microbes leading to hypersensitivity towards many common food components later in life. It has been shown that certain lactic acid bacteria (probiotics) for example, are able to modulate the immune system. The mechanisms are not yet known. It has been demonstrated that ingestion of probiotics can alleviate hypersensitivity and eczema in children. There are strong indications that probiotics may possess cancer preventive properties by suppression of pre-neoplastic changes in colon and prevention of oxidative DNA damages. The proportion and composition of probiotic microbes as part of the intestinal flora is dependent of many factors such as eating habits and life style. Being mainly saprophytes probiotic bacteria depend on fermentable carbohydrates in the colon. Prebiotics designate carbohydrates (food-fibres) that are indigestible in the small intestine but fermentable by probiotic bacteria. Some prebiotics exert a selective function. Especially fructo oligosaccharides (FOS) seem to stimulate bifidobacteria but the specific effect of different oligosaccharides towards different probiotic bacteria is not sufficiently investigated.