The Effect of Prebiotic Synergy1 Supplementation on Microbiota, Protein Metabolism and Gastrointestinal (GI) Symptoms in People Consuming High Protein Diet

The composition and metabolism of human gut microbiota play crucial roles in health. Microbial colonisation of the gastrointestinal tract varies widely, with the large intestine having not only the highest density of microbes in terms of bacterial cells per gram but also the most metabolically active microbial community. Genetics, mode of birth, infant feeding patterns, antibiotic usage, sanitary living conditions and long term dietary habits contribute towards shaping the composition of the gut microbiome. Diet clearly has a major impact on variation in the gut microbiota composition, and this can be detected in faecal samples after only a few days. The bacterial metabolism of dietary components produces much chemical diversity in the large intestine with protective or detrimental effects on disease development.

Dietary protein levels are relatively high in western European populations, up to 103g/d, as reported by Food and Agriculture Organization. This may result in high levels, entering the large gut where it can become a substrate for proteolytic bacteria. Protein specifically can provide nutrition for microorganisms but metabolites from bacterial protein breakdown can be detrimental. Protein intake from the diet might not be the only source of microbial proteolysis; the human body also secretes considerable amounts of protein into the digestive lumen which can potentially be used by the microflora. On the contrary, end products of carbohydrate metabolism can be positive for health. In this context, prebiotics are carbohydrates that are resistant to digestion and can become available for bacteria in the colon to produce short chain fatty acids and inhibit the production of harmful metabolites. A switch towards more carbohydrate metabolism in the colon, at the expense of proteolysis therefore has positive capacity through the production of more benign metabolites.

Rationale for design Prebiotics are dietary ingredients that target carbohydrate digesting bacteria only. Given the high intake levels of protein in Western populations, they may be useful to modulate the composition/activity of the microbial gut ecology for improved health.

Among prebiotic nutrients, inulin-type fructans (ITF) are well characterized and their administration promotes growth of beneficial microorganisms like Bifidobacterium spp. .These microorganisms are involved in the reduction of intestinal endotoxin concentration, improve glucose tolerance, exert benefits upon immune function and inhibit pathogens. In healthy individuals, ITF intake promotes satiety and modulates gut peptides regulating food intake.

The aim of the present study is to investigate the effect of inulin-type fructans (ITF) on the negative consequences of colonic fermentation in individuals consuming high protein diets. The hypothesis to be tested is that their action promotes carbohydrate degrading bacteria at the expense of protein utilisers.