Defining meal requirements for protein to optimize metabolic roles of amino acids.
Level 5 - mechanism / opinion, no new human data
Narrative review and expert perspective synthesizing literature without original trial data or systematic search methodology.
PubMed 25926513 · doi:10.3945/ajcn.114.084053
What was done
This is a narrative review synthesizing literature on essential amino acids as meal-based metabolic signals (including leucine-induced mTORC1 activation, GCN2, GLP-1, PYY, serotonin, and insulin). It examines the concept of a per-meal protein threshold for skeletal muscle protein synthesis and evaluates how advancing age, physical inactivity, and resistance exercise alter these requirements.
What was found
The abstract presents synthesized benchmarks from prior literature rather than new experimental data. It reports that older adults require daily protein intakes of ≥1.0 g/kg (compared to standard recommendations of 0.8 g/kg) and identifies anabolic and metabolic benefits from consuming at least 20–30 g of protein at a given meal. Resistance exercise is described as increasing the efficiency of essential amino acid use for muscle anabolism and lowering the per-meal threshold needed to stimulate protein synthesis.
Why it matters
It emphasizes shifting dietary guidance from single daily protein totals to per-meal protein redistribution (e.g., 20–30 g across three meals) to overcome age- or inactivity-related declines in muscle protein synthesis.
Limits
The abstract describes a narrative review without original data, systematic review methodology, or meta-analytic pooling. Specific effect sizes, confidence intervals, sample sizes, and participant characteristics of the underlying studies are not reported in the abstract.
Cited by
- supports Older adults require a higher amount of leucine per serving (around 2.5 grams or more) to trigger muscle protein synthesis due to anabolic resistance.