[Urea as a substrate for the intestinal flora of the infant (author's transl)].

The significance of the relatively high urea content of mothers milk for infant nutrition was investigated using 15N urea as a tracer by oral loading tests and an in-vitro culturing of bifidobacteria. The urea level of 6 mother's milk specimens was found to be 295 +/- 49 mg/l. There was a distinct incorporation of 15N into the intestinal bacterial fraction following 15N urea loadings in 3 infants, receiving mother's milk and 2 cows milk formulas which contained 1.8 and 2.1% of protein. The incorporation rate did not differ between the single types of feeding. In contrast to these findings the 15N incorporation into the bacterial flora of an infant suffering from kidney insufficiency was about 30 times higher than in healthy infants. Bifidobacteria infants derived from the feces of a breastfed infant utilised 15N from 15N urea added to the culture medium in concentrations of 20 mg per 100 ml. After incubating the culture for 2 days at 37 degrees C the 15N-excess of nitrogen fraction of the bifidobacteria amounted to 0.47 atom-%. Urea therefore can directly serve as a substrate for bifidobacteria on mother's milk feeding.