title: Ileal losses of nitrogen and amino acids in humans and their importance to the assessment of amino acid requirements.
abstract: OBJECTIVE
  Irreversible amino acid losses at the human ileum are not taken into account when tracer-derived amino acid requirements are calculated because the data available are scarce. We have investigated amino acid losses at the ileal level in humans after ingestion of a protein meal.
  
  
  METHODS
  Thirteen volunteers ingested a single meal of 15N milk or soy proteins. The appearance of 15N and 15N amino acids in the ileal effluents collected using an ileal tube was monitored for 8 hours.
  
  
  RESULTS
  In the soy group, higher losses of endogenous nitrogen, especially originating from amino acids, were observed, as well as a higher flow rate of dietary non-amino acid nitrogen. With soy protein, the digestibilities of valine, threonine, histidine, tyrosine, alanine, and proline were significantly lower than with milk. Ileal losses of leucine, valine, and isoleucine amounted to 12, 10, and 7 mg x kg(-1) x day(-1), respectively. Threonine ileal loss (9-12 mg x kg(-1) x day(-1)) was particularly high compared with the current amino acid requirement.
  
  
  CONCLUSIONS
  Amino acid losses at the human terminal ileum are substantial and depend on the type of dietary protein ingested. Although it remains unclear whether intact amino acids are absorbed in the colon, we suggest that ileal losses should be considered an important component of amino acid requirements.
authors.affiliation: Institut National de la Recherche Agronomique, Unité de Physiologie de la Nutrition et du Comportement Alimentaire, Paris, France. gaudicho@inapg.inra.fr
authors.forename: Claire
authors.initials: C
authors.lastname: Gaudichon
authors.forename: Cécile
authors.initials: C
authors.lastname: Bos
authors.forename: Céline
authors.initials: C
authors.lastname: Morens
authors.forename: Klaus J
authors.initials: KJ
authors.lastname: Petzke
authors.forename: François
authors.initials: F
authors.lastname: Mariotti
authors.forename: Julia
authors.initials: J
authors.lastname: Everwand
authors.forename: Robert
authors.initials: R
authors.lastname: Benamouzig
authors.forename: Sophie
authors.initials: S
authors.lastname: Daré
authors.forename: Daniel
authors.initials: D
authors.lastname: Tomé
authors.forename: Cornelia C
authors.initials: CC
authors.lastname: Metges
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000378:metabolism*; D004032:Diet; D004063:Digestion; D006801:Humans; D007082:Ileum / Q000378:metabolism*; D008894:Milk Proteins; D009584:Nitrogen / Q000008:administration & dosage / Q000378:metabolism*; D009751:Nutritional Requirements; D030262:Soybean Proteins
chemical_list: D000596:Amino Acids; D008894:Milk Proteins; D030262:Soybean Proteins; D009584:Nitrogen