Influence of a transgalactooligosaccharides‐enriched diet on fecal microflora and on immunity in mice

Prebiotics are non‐digestible food ingredients providing a beneficial effect on the host by stimulating a health promoting indigenous microflora. Transgalactooligosaccharides (TOS) are usually considered as prebiotics. Our aim was to study the effect of the ingestion of a TOS‐enriched diet on fecal microflora and immune response in mice. 40 female BALB/c mice were fed with basal diet or diets containing 5% of either lactose or TOS during 4 weeks. Microbiological analyses of feces were performed on days 0, 14 and 28. Serum and fecal total immunoglobulins were measured by ELISA on day 28. Phagocytose activity, NK cells cytotoxic activity and T‐lymphocytes phenotype were determined by flow cytometry in spleen and Peyer’s patches (PP) at the end of the experiment (day 28). Microbiological analyses of feces revealed that ingestion of the TOS‐enriched diet modified the number of Bifidobacteria (P=0.0048) and Lactobacilli (P=0.0115). Serum IgM concentration was lowered by consumption of TOS (P=0.0015). In spleen we observed that mice consuming TOS had lower rate of CD3+CD4+ cells (P=0.0369) but greater rate of CD3‐CD4+ cells (P=0.0497). In PP no significant difference between diets was observed. This study showed that TOS modify the composition of the fecal flora and modulate the systemic but not intestinal immunity in mice. Whether this effect is direct or microflora‐mediated remains to be elucidated.