title: Increasing habitual protein intake accentuates differences in postprandial dietary nitrogen utilization between protein sources in humans.
abstract: It is appropriate to characterize the nutritional value of dietary proteins in humans through the specific study of dietary nitrogen metabolism during the postprandial period. However, the influence of the habitual protein intake on this variable has not been studied. We aimed to describe the influence of prior protein intake on the specific metabolic utilization of dietary nitrogen in humans. Healthy men and women were adapted for 7 d to two diets with a normal [NP, 1 g/(kg x d)] and high protein content [HP, 2 g/(kg x d)]. After each period, they were studied for an 8-h postmeal period after ingesting a single (15)N-labeled mixed meal (0.41 g/kg protein) containing either milk (n = 12) or soy protein (n = 8). The HP diet reduced the peak of dietary N incorporation into free serum amino acids in the soy group but had no effect in the milk group. The incorporation of dietary N into plasma protein was higher after soy than after milk protein, but habitual protein level had no effect. The postprandial retention of milk protein was reduced by the HP diet compared with the NP diet by only 5% and that of soy protein was diminished by 13% (protein source: P < 0.0001, protein level: P < 0.0001, interaction: P < 0.001). In conclusion, the efficiency of the meal N postprandial retention was lower after HP adaptation, but this decrease was much more pronounced for soy than for milk protein, indicating that increasing the habitual protein intake accentuates differences in metabolic utilization among dietary proteins.
authors.affiliation: Institut National de la Recherche Agronomique, Unité de Physiologie de la Nutrition et du Comportement Alimentaire, Institut National Agronomique Paris-Grignon, 75005 Paris, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Morens
authors.forename: Cécile
authors.initials: C
authors.lastname: Bos
authors.forename: Maria E
authors.initials: ME
authors.lastname: Pueyo
authors.forename: Robert
authors.initials: R
authors.lastname: Benamouzig
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gausserès
authors.forename: Catherine
authors.initials: C
authors.lastname: Luengo
authors.forename: Daniel
authors.initials: D
authors.lastname: Tomé
authors.forename: Claire
authors.initials: C
authors.lastname: Gaudichon
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage*; D005215:Fasting / Q000097:blood; D005247:Feeding Behavior; D005260:Female; D006728:Hormones / Q000097:blood; D006801:Humans; D008297:Male; D009574:Nitro Compounds / Q000097:blood; D009584:Nitrogen / Q000008:administration & dosage* / Q000378:metabolism*; D019518:Postprandial Period
chemical_list: D001786:Blood Glucose; D004044:Dietary Proteins; D006728:Hormones; D009574:Nitro Compounds; D009584:Nitrogen