Protein Requirements during Aging.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing metabolic tracer methodology without a systematic review protocol.
PubMed 27529275 · doi:10.3390/nu8080492
What was done
The authors reviewed methodologies for evaluating dietary protein requirements in younger versus older adults, specifically comparing traditional nitrogen balance approaches with the indicator amino acid oxidation (IAAO) method.
What was found
Current nitrogen balance recommendations establish the Estimated Average Requirement (EAR) at 0.66 g/kg/day and Recommended Dietary Allowance (RDA) at 0.8 g/kg/day. By contrast, IAAO estimates were 0.9 g/kg/day (EAR) and 1.2 g/kg/day (RDA) for young and older adults, which are ~40% higher than current recommendations on a body-weight basis and 40% higher than estimates in young men when normalized to fat-free mass.
Why it matters
These findings suggest standard dietary protein guidelines may underestimate daily requirements in aging populations who face anabolic resistance.
Limits
The abstract describes a narrative review without detailing sample sizes, study counts, or systematic search criteria. Estimates rely on acute metabolic indicator amino acid oxidation rather than longitudinal randomized trials evaluating muscle mass, strength, or functional outcomes.
Cited by
- supports Historical nitrogen balance studies showed that most people maintain neutral balance at 0.66 g protein/kg/day, leading to the 0.8 g/kg/day dietary recommendation.