Does casein protein enhance muscle collagen adaptation?
Exercise stimulates muscle growth and strength gains. In addition, exercise stimulates adaptations of the connective tissue inside (muscle collagen) and outside (tendons) of the muscle, to allow proper force transfer from the muscle to the bones.
Our study investigated whether casein protein (the main milk protein) can further increase muscle collagen synthesis during overnight recovery. Subjects either 1) received 30 g casein protein before sleep, 2) did exercise in the evening, 3) or did exercise in the evening and received 30 g casein protein before sleep.
Evening resistance exercise increased muscle collagen synthesis during the night. However, there was no added effect of casein ingestion.
It should be noted that casein is not very high in proline and glycine, the two major building blocks (amino acids) for collagen. Whether higher doses or other protein sources that are higher in these amino acids (e.g. gelatin or collagen) can further stimulate collagen synthesis remains to be determined.
Our open-access study:
Trommelen et al. Casein ingestion does not increase muscle connective tissue protein rates. Med Sci Sports Exerc, 2020
More detailed discussion of the study:
Casein Ingestion Does Not Increase Muscle Connective Tissue Protein Synthesis Rates
Go to the next infographic in the protein series:
Processing of milk lowers protein absorption?
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