The indicator amino acid oxidation (IAAO) technique: a novel approach to assess protein intakes that maximize whole-body protein anabolism.
Level 5 - mechanism / opinion, no new human data
Narrative review and methodological commentary without systematic review methodology or new human data.
PubMed 40748779 · doi:10.1080/10408398.2025.2541895
What was done
This narrative review evaluated the methodological framework and physiological interpretation of the Indicator Amino Acid Oxidation (IAAO) breakpoint method compared with classical nitrogen balance methodology for assessing human dietary protein requirements, based on published literature.
What was found
The authors note that traditional nitrogen balance methodology set the Recommended Daily Allowance (RDA) at 0.83 g protein·kg BM⁻¹·d⁻¹, whereas IAAO breakpoint analysis yields an estimate of 1.20 g protein·kg BM⁻¹·d⁻¹. The review argues that IAAO breakpoint analysis reflects the protein intake at which whole-body protein net balance is maximized rather than a maintenance requirement. It details three specific methodological issues in current IAAO applications: extrapolation of hourly rates to daily totals, extrapolation from free amino acid sip-feeding to whole-food dietary patterns, and statistical misinterpretation of the 95% confidence interval upper bound as covering 98% of the population.
Why it matters
This paper clarifies that IAAO-derived values reflect intakes that maximize whole-body protein anabolism rather than minimal baseline requirements for maintaining equilibrium.
Limits
The paper is a narrative review presenting methodological critique and expert commentary without new human experimental data or systematic review methodology.
Cited by
- supports Nitrogen balance studies used to establish the RDA for protein are prone to errors due to incomplete collection and overestimation of nitrogen losses.