Bioavailability of urea nitrogen for the low birthweight infant

S. M. Donovan, B. Lonnerdal, S. A. Atkinson

Research output: Contribution to journalArticlepeer-review


Previous studies have demonstrated increase retention (40%) of dietary urea nitrogen by term infants recovering from infection compared to healthy infants (13%), possibly due to a higher requirement for nitrogen. Since low birthweight infants also have a high requirement for nitrogen, the bioavailability of urea nitrogen was investigated in low birthweight infants using 15N, 15N-urea. Four low birthweight infants (gestational age = 30 ± 2.2 weeks [mean ± SD], birthweight = 1.4 ± 0.3 kg) were fed formula enriched with 15N, 15N-urea. Metabolic balance studies (72 hours) were performed with urine and fecal collections. Nitrogen was quantitated by Kjeldahl analysis and 15N, 15N-urea by gas chromatography/mass spectrometry. Mean nitrogen intake was 489 ± 32 mg/kg/d, with 75% nitrogen absorption and 62% nitrogen retention. Maximum urinary enrichment was 8%. Cumulative 15N, 15N-urea excretion was 72%, resulting in 28% retention. Thus the bioavailability of urea nitrogen for low birthweight infants appears to be intermediate between compromised and normal term infants.

Original languageEnglish (US)
Pages (from-to)899-905
Number of pages7
JournalActa Paediatrica Scandinavica
Issue number10
StatePublished - 1990
Externally publishedYes


  • Infant formula
  • Low birthweight infants
  • Nitrogen
  • Non-protein nitrogen
  • Stable isotopes
  • Urea nitrogen

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health


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