INFLUENCE OF DIETARY-PROTEIN SUPPLEMENTS ON THE FORMATION OF BACTERIAL METABOLITES IN THE COLON

Background - To evaluate the influence of increased dietary protein in take on bacterial colonic metabolism in healthy volunteers. Methods - Short chain fatty acids, ammonia, and volatile organic compounds in fa ecal samples, and phenols in the urine of five volunteers were measure d after one week of basal nutrient intake and after one week of a diet supplemented with a protein rich food (Fortimel; Nutricia, Zoetermeer , The Netherlands). Paired t tests and factor analysis were used for s tatistical analysis. Results - Total energy and resistant carbohydrate intake remained unchanged in each study period. The percentage energy delivered as dietary protein, increased significantly (from 15.4% to 23.8%; p=0.007) during supplement intake. A significant increase in fa ecal ammonia (p=0.002), faecal valeric acid (p=0.02), and urinary p-cr esol (p=0.04) was noted during supplementary protein intake. A total o f 120 different volatile compounds were isolated from the faecal sampl es of which 10 increased significantly during dietary protein suppleme ntation. The change in volatile pattern, especially for S containing m etabolites, was clearly shown by a factor analysis model which made a distinction between the two dietary regimens for all volunteers. Concl usion - An increase in dietary protein leads to altered product format ion by colonic metabolism, mainly reflected by an increase in faecal a mmonia, faecal volatile S substances, and urinary p-cresol.