Lactalbumin, Not Collagen, Augments Muscle Protein Synthesis with Aerobic Exercise.
Level 2 - randomized trial
Individual randomized crossover trial in humans
PubMed 31895298 · doi:10.1249/MSS.0000000000002253
What was done
In a double-blind randomized crossover trial, 11 endurance-trained participants (5 men, 6 women; aged 24 ± 4 years, peak power 320 ± 48 W) consumed a controlled diet providing 1.0 g/kg/d protein and ceased habitual training for 11 days. Participants completed two intensified aerobic training phases consisting of 4 × 4-min cycling intervals at 70% peak power output on 3 consecutive days. In each phase, they received either alpha-lactalbumin (LA) or isonitrogenous collagen peptides (CP) as 20 g post-exercise and 40 g pre-sleep, separated by a 4-day washout period without supplementation. Fractional synthetic rates of myofibrillar (MyoPS) and sarcoplasmic (SarcPS) proteins were measured using deuterium oxide, along with plasma amino acids and sleep quality parameters.
What was found
LA ingestion led to significantly greater increases in plasma leucine (P < 0.001) and tryptophan (P < 0.001) concentrations compared with CP. Both LA and CP increased MyoPS and SarcPS above the washout phase (P < 0.01). However, the increases in protein synthesis were significantly greater with LA than CP, with MyoPS being 13% ± 5% greater (P < 0.01) and SarcPS being 5% ± 7% greater (P < 0.01). Sleep quality data were not quantitatively reported in the abstract.
Why it matters
This study demonstrates that protein quality and amino acid composition (high leucine and tryptophan), not total nitrogen intake alone, drive post-exercise muscle protein synthesis following endurance training.
Limits
The study had a very small sample size (n = 11) and evaluated a short 3-day training intervention. Long-term training adaptations, functional performance outcomes, and numerical results for sleep quality metrics were not reported in the abstract.