Impact of prebiotics on human health.

It is becoming clear that intestinal microflora plays an important role in the development of local and systemic immune response. Nutritional ingredients have been added to infant formula in an attempt to make its composition similar to that of human milk. The effects of these modifications have been observed in the composition of intestinal microflora. Prebiotics are non-digestible foods able to selectively stimulate the growth/activity of a limited number of colonic bacteria. A mixture of galacto-oligosaccharides and fructo-oligosaccharides (GOS/FOS) induces an increase in Bifidobacteria, similar to that of breast-fed infants. What is less clear is whether the modifications of intestinal microflora obtained by functional foods are associated with clinically measurable effects. Preliminary indirect data suggest that increasing the load of Bifidobacteria and Lactobacilli may protect from infections and allergies and this effect may persists beyond infancy. The emerging concept is that early nutritional intervention may be effective in modifying the intestinal microflora composition in a phase in which microbiological imprinting may drive immunological imprinting thereby producing clinical effects. Further investigations and well designed randomised clinical trials are needed to demonstrate the potential beneficial effects and to exclude the potential side effects.