Milk Promotes Muscle Protein Synthesis Better Than Beef Post-Exercise
Title: Differences in postprandial protein handling after beef compared with milk ingestion during post-exercise recovery: a randomized controlled trial
Author: Burd et al
Journal: American Journal of Clinical Nutrition
Objective: They ‘aimed to compare protein digestion and absorption kinetics, postprandial amino acid availability, anabolic signaling, and the subsequent myofibrillar protein synthetic response after the ingestion of milk compared with beef during recovery from resistance-type exercise’.
The following are known to influence postprandial muscle protein synthesis:
- Protein intake
- Absorption kinetics
- Amino acid composition
These promote an increase in essential amino acids, including the BCAA leucine
Most research has looked at whey or soy protein supplements. Dairy has also been well studied. However, the research is limited looking at typical meal patterns in western diets, of which beef is a commonly ingested protein source.
The authors sought to shed some light on dairy vs animal meat, specifically beef.
12 healthy young males performed a single bout of resistance exercise.
Immediately after completing the exercise, participants ingested 30 g protein by consuming either isotopic radiolabeled labeled beef or milk.
They then assessed protein digestion and absorption kinetics, plasma amino acid availability, anabolic signaling, and subsequent myofibrillar protein synthesis rates by using radiolabeled amino acids phenylalanine and tyrosine.
Beef-derived protein appeared in circulation more quickly than milk.
Beef phenylalanine was more available than milk post-exercise, although this was not statistically significant (P = 0.08).
Both rapamycin complex 1 and 70-kDa S6 protein kinase 1 activity, which are associated with protein synthesis, were increased following milk or beef ingestion during post-exercise recovery.
Milk ingestion increased myofibrillar protein synthesis rates more than did beef ingestion during both the 0- to 2-h postexercise phase (P = 0.013).
However, the increase in myofibrillar protein synthesis rates did not differ at the 5 hour mark postexercise(P = 0.114).
Both milk and beef increased muscle protein synthesis
At the 0 and 2 hour mark, milk had a significantly increased rate of synthesis, although this difference subsided at the 5 hour mark.
Interestingly, beef had more readily available phenylalanine.
The significance of this regarding long term muscle growth is unclear.
Burd, N. A., Gorissen, S. H., & Vliet, S. V. (2015). Differences in postprandial protein handling after beef compared with milk ingestion during postexercise recovery: a randomized controlled trial. American Journal of Clinical Nutrition,102(4), 828-836. doi:10.3945/ajcn.114.103184