[New knowledge of protein nitrogen resorption in the colon]

The absorption of protein nitrogen by the colon was assessed in 8 infants with colostomy by giving [15N] yeast protein in a dosage of 5-20 mg 15N/kg (92.4 atom-% 15N). The absorption of 15N ranged between 87.1 and 98.1% of the administered dose, and the retention in the protein pool ranged between 81.0 and 95.7%. The incorporation of 15N in the plasma proteins was demonstrated by 15N-excess values between 0.01 and 0.10 atom-%, the TCA soluble fraction contained 15N-excess values of 0.04 to 0.19 atom-%. The results suggest that the colon can assimilate proteins when insufficient absorption of protein nitrogen in the small intestine occurs. The breakdown of protein is thought to result from the action of the colonic flora.