The anabolic response to protein ingestion during recovery from exercise has no upper limit in magnitude and duration in vivo in humans.
Level 2 - randomized trial
Individual human intervention trial using isotope tracer methodology
PubMed 38118410 · doi:10.1016/j.xcrm.2023.101324
What was done
Researchers evaluated the human anabolic response during post-exercise recovery after the ingestion of 100 g versus 25 g of protein using a quadruple isotope tracer feeding-infusion approach. Measured outcomes included dietary-protein-derived plasma amino acid availability, muscle protein incorporation, whole-body protein net balance, mixed-muscle, myofibrillar, muscle connective, and plasma protein synthesis rates, as well as whole-body protein breakdown and amino acid oxidation rates over a duration exceeding 12 hours.
What was found
Ingestion of 100 g of protein induced a greater and more prolonged (>12 h) anabolic response compared with 25 g of protein. There was a dose-response increase in plasma amino acid availability and incorporation into muscle protein. The 100 g bolus increased whole-body protein net balance, mixed-muscle, myofibrillar, muscle connective, and plasma protein synthesis rates. Protein ingestion showed a negligible impact on whole-body protein breakdown rates or amino acid oxidation rates. No exact numerical point estimates, standard deviations, or p-values were reported in the abstract.
Why it matters
These findings challenge the prevailing paradigm that single-meal protein utilization for muscle protein synthesis saturates at 20–30 g, demonstrating sustained utilization and anabolism with larger doses.
Limits
The abstract does not state the sample size (n), participant characteristics (age, sex, training status), or quantitative statistical values. Long-term functional adaptations such as chronic muscle hypertrophy or strength changes were not measured.