[Probiotics]

The colonic flora is thought to play a key role in human health. Gut bacteria produce desirable as well as undesirable metabolites from fermentation and sometimes they may act as pathogens. Composition as well as activities of the gut bacteria can be influenced by nutrition. Prebiotics are food ingredients that selectively stimulate the growth of colonic bacteria regarded as beneficial, i. e. bifidobacteria and lactobacilli. Fructose polymers (fructo-oligosaccharides, inulin), galacto-oligosaccharides and soya oligosaccharides were shown to exert prebiotic activities. In adults, the growth of bifidobacteria was stimulated especially by inulin and fructo-oligosaccharides. Infant formulas containing galacto-oligosaccharides and inulin promoted the growth of bifidobacteria in faeces of bottle-fed infants and resulted in stool characteristics similar to those found in breast-fed infants. However, at present there is only limited knowledge on the long-term health consequences of increased counts of bifidobacteria. In adults, prebiotics can enhance the absorption of calcium from the colon. They can increase stool frequency and are mildly laxative. Prebiotic consumption is usually accompanied by mild flatulence and in sensitive persons by more severe gastrointestinal symptoms. In contrast to the results of animal experiments, a significant lipid-lowering action of fructo-oligosaccharides has not been found in humans. In animals, fructo-oligosaccharides have shown a favourable effect on experimental carcinogenesis. Whether or not these findings may apply to humans will be subject of future studies.