The effects of fermented milks with simple and complex probiotic mixtures on the intestinal microbiota and immune response of healthy adults and children

This study compared the effect of two functional fermented milks with simple and complex probiotic mixtures on the microbiota and some immune system functions of healthy adults and children. The complex yogurt, containing Lactobacillus casei and other strains of lactobacilli and bifidobacteria, and the simple yogurt, containing only L. casei, were administered daily to healthy volunteers (41 adults and 36 children) for a period of 4 weeks. Microbiological and molecular analyses of faecal samples indicated that the complex product induced a larger increase in the lactic acid bacteria number, compared with the simple product, without significant alterations of the autochthonous species composition. Of the probiotic strains, L. casei showed the best survival rate in faeces. The influences of both products on the immune system were similar, with increase of NK activity and proliferative response to Candida albicans in adults and secretory-IgA in children saliva, indicating that immunomodulating properties were probably supported by common traits in the two products.