Hydrolyzed casein and whey protein meals comparably stimulate net whole-body protein synthesis in COPD patients with nutritional depletion without an additional effect of leucine co-ingestion.
Level 2 - randomized trial
Randomized, double-blind crossover trial
PubMed 23886411 · doi:10.1016/j.clnu.2013.06.014
What was done
Twelve nutritionally depleted COPD patients (GOLD stage II–IV) completed a double-blind randomized crossover study comparing the metabolic response to a 15 g hydrolyzed casein (hCAS) versus hydrolyzed whey (hWHEY) protein meal, with or without leucine co-ingestion. Stable isotope tracers (continuous intravenous L-[ring-2H5]-phenylalanine, L-[ring-2H2]-tyrosine, and L-[2H3]-3-methylhistidine, along with meal-added oral L-[15N]-phenylalanine) and LC/MS/MS plasma analysis were used to assess whole-body protein breakdown (WbPB), whole-body protein synthesis (WbPS), net protein synthesis (NetPS), splanchnic extraction, and myofibrillar protein breakdown (MPB).
What was found
WbPS was significantly higher following the hCAS meal compared to hWHEY (P < 0.05), whereas hWHEY resulted in greater reduction of WbPB (P < 0.01). NetPS was stimulated to a comparable degree by both proteins, with a protein conversion rate greater than 70%. Leucine co-ingestion did not alter insulin, WbPB, WbPS, or MPB. Absolute quantitative kinetic values and confidence intervals were not provided in the abstract.
Why it matters
This study shows that hydrolyzed casein and whey are equally effective at acutely stimulating net whole-body protein anabolism in depleted COPD patients via distinct kinetic mechanisms (synthesis stimulation versus breakdown suppression), and that adding leucine provides no added acute benefit.
Limits
The study is limited by a small sample size (n = 12) and an acute single-meal design that measured whole-body kinetic markers rather than long-term clinical outcomes, muscle mass accretion, or functional exercise capacity.
Cited by
- contradicts Combining leucine-rich essential amino acids with whey protein powder makes the whey protein powder more effective at stimulating protein synthesis.