Ileal losses of nitrogen and amino acids in humans and their importance to the assessment of amino acid requirements.
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.
Gaudichon
Claire
C
Institut National de la Recherche Agronomique, Unité de Physiologie de la Nutrition et du Comportement Alimentaire, Paris, France. gaudicho@inapg.inra.fr
Bos
Cécile
C
Morens
Céline
C
Petzke
Klaus J
KJ
Mariotti
François
F
Everwand
Julia
J
Benamouzig
Robert
R
Daré
Sophie
S
Tomé
Daniel
D
Metges
Cornelia C
CC
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
D000596:Amino Acids; D008894:Milk Proteins; D030262:Soybean Proteins; D009584:Nitrogen