title: Examination of Chinese habitual dietary protein requirements of Chinese young female adults by indicator amino acid method.
abstract: OBJECTIVE
  To determine protein requirement of Chinese young female adults on habitual Chinese diet through indicator amino acid oxidation (IAAO) technique.
  
  
  METHODS
  Twenty women with a mean (SD) age of 21.6 (0.9) years were healthy based on questionnaire, physical examinations and screening tests. There were three consecutive periods of 7 days each with six different intakes of protein (0.70, 0.78, 0.86, 0.94, 1.02 and 1.10 g/kg·d) within Chinese habitual diets (proportions of good-quality protein were 40 to 45%). Subjects were randomly allocated equally into two groups (1.10, 0.86, 0.78 g/kg·d for group 1 and 1.02, 0.94, 0.70 g/kg·d for group 2 from period 1 to period 3 in turn). Adaptation days were from day 1 to day 6 and the isotope study day was day 7 in each period. Amino acid kinetics was measured in non-menstrual periods, based on the IAAO technique. Two indicators (rate of release of 13CO2 and rate of leucine oxidation) were used to estimate protein requirement by breakpoint analysis with a two-phase linear regression crossover model.
  
  
  RESULTS
  Mean and population safe protein requirements of Chinese habitual diets in non-menstrual periods from the rate of release of 13CO2 were 0.91 and 1.09 g/kg·d, respectively. And from the rate of leucine oxidation were 0.92 and 1.10 g/kg·d, respectively.
  
  
  CONCLUSIONS
  The protein requirement of young women on Chinese habitual diets in non-menstrual period was lower than the current protein reference intake for Chinese females. Further studies are necessary to explore female protein requirements during the whole menstrual cycle.
authors.affiliation: Laboratory of trace element nutrition MOH, Institute of nutrition and food safety, Chinese Center for Disease Control and Prevention, Beijing, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Tian
authors.forename: Jianmin
authors.initials: J
authors.lastname: Liu
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jianhua
authors.initials: J
authors.lastname: Piao
authors.forename: Lingyan
authors.initials: L
authors.lastname: Gou
authors.forename: Yuan
authors.initials: Y
authors.lastname: Tian
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.forename: Yibing
authors.initials: Y
authors.lastname: Ji
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Yang
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D002681:China; D018592:Cross-Over Studies; D004032:Diet / Q000379:methods* / Q000706:statistics & numerical data; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D006801:Humans; D007930:Leucine / Q000378:metabolism; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D012016:Reference Values; D055815:Young Adult
chemical_list: D000596:Amino Acids; D015415:Biomarkers; D004044:Dietary Proteins; D007930:Leucine