Abstract/Summary

In Europe and Northern America, protein intake is high, whilst fibre intake is relatively low. With large amounts of protein entering the colon, bacterial proteolysis may have some negative effects through potentially toxic end-products. Prebiotics could have the potential to reverse negative consequences of gut bacterial protein fermentation. Single stage, pH controlled, anaerobic, stirred batch culture systems simulating the distal colon were applied first with faecal inoculum from both omnivore and vegetarian volunteers. Fermentation of different protein sources with and without supplementation of inulin type fructans (ITF) were tested. A significant increase of bifidobacteria was observed with the addition of the ITF together with lower concentrations of protein fermentation metabolites (BCFA and ammonia). Three-stage continuous colonic model systems simulating the whole colon were then studied with both omnivore and vegetarian volunteers. Casein, with and without two different doses of ITF were assessed. A significantly higher number of bifidobacteria and reduction of bacteroides and Desulfovibrio spp. were found with ITF addition. Furthermore, production of metabolites from protein fermentation (BCFA and ammonia) was significantly lowered with ITF. To confirm the health benefit of ITF on high protein population in vivo, 43 volunteers were recruited to complete a randomised, double blind, cross over trial. A significant increase in bifidobacteria and a decrease in Desulfovibrio spp. was confirmed with the addition of prebiotic treatment. Stool frequency was significantly higher with ITF as compared to the placebo group, with a trend towards softness as based on the Bristol scale. Total bacteria and bifidobacteria changes during interventions were significantly correlated with stool frequency. In conclusion, all three phases of the project found favourable bacterial and metabolic changes with ITF supplementation. ITF had inhibitory effects on colonic microbial proteolysis, and could exert health benefit for high protein consumers, especially those who also consume low fibre diet.