title: Methods to assess amino acid requirements in humans.
abstract: OBJECTIVE
  There are now different stable isotopic methods to measure minimum daily human indispensable amino acid (IAA) requirements. There has been debate on the appropriateness of statistical methods used to define the nature of change in the response.
  
  
  RESULTS
  Current isotopic methods measure daily amino acid oxidation and balance of the IAA under test, or of a selected indicator amino acid, to graded intakes of the test IAA. A key concern is how response curves of oxidation/balance are analyzed to find the inflection point (breakpoint) at which the intake requirement is identified. Evaluating the pattern of the response to identify a breakpoint by a two-phase regression appears best. The indicator amino acid oxidation method has also been shortened and developed into a noninvasive protocol suitable for different populations and age groups.
  
  
  CONCLUSIONS
  The indicator amino acid oxidation and balance method might be considered the best approach currently available, but it is challenging. The short-term indicator oxidation method is noninvasive and nondemanding. IAA requirements, based on these methods, have implications for the quality of protein in the dietary intake of populations. Methods that assess the IAA requirements to support optimal body function also need to be developed.
authors.affiliation: St. John's Research Institute, St. John's National Academy of Health Sciences, Bangalore, India. a.kurpad@sjri.res.in
authors.forename: Anura V
authors.initials: AV
authors.lastname: Kurpad
authors.forename: Tinku
authors.initials: T
authors.lastname: Thomas
mesh_terms: D000601:Amino Acids, Essential / Q000378:metabolism*; D004032:Diet; D004044:Dietary Proteins / Q000378:metabolism*; D002149:Energy Intake; D006801:Humans; D007554:Isotopes; D015596:Nutrition Assessment; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D011865:Radioisotope Dilution Technique
chemical_list: D000601:Amino Acids, Essential; D004044:Dietary Proteins; D007554:Isotopes