Effects of Whey, Caseinate, or Milk Protein Ingestion on Muscle Protein Synthesis after Exercise

Nutrients. 2016 Jun 3;8(6):339. doi: 10.3390/nu8060339.


Whey protein (WP) is characterized as a "fast" protein and caseinate (CA) as a "slow" protein according to their digestion and absorption rates. We hypothesized that co-ingestion of milk proteins (WP and CA) may be effective for prolonging the muscle protein synthesis response compared to either protein alone. We therefore compared the effect of ingesting milk protein (MP) to either WP or CA alone on muscle protein synthesis after exercise in rats. We also compared the effects of these milk-derived proteins to a control, soy protein (SP). Male Sprague-Dawley rats swam for two hours. Immediately after exercise, one of the following four solutions was administered: WP, CA, MP, or SP. Individual rats were euthanized at designated postprandial time points and triceps muscle samples collected for measurement of the protein fractional synthesis rate (FSR). FSR tended to increase in all groups post-ingestion, although the initial peaks of FSR occurred at different times (WP, peak time = 60 min, FSR = 7.76%/day; MP, peak time = 90 min, FSR = 8.34%/day; CA, peak time = 120 min, FSR = 7.85%/day). Milk-derived proteins caused significantly greater increases (p < 0.05) in FSR compared with SP at different times (WP, 60 min; MP, 90 and 120 min; CA, 120 min). Although statistical analysis could not be performed, the calculated the area under the curve (AUC) values for FSR following this trend were: MP, 534.61; CA, 498.22; WP, 473.46; and SP, 406.18. We conclude that ingestion of MP, CA or WP causes the initial peak time in muscle protein synthesis to occur at different times (WP, fast; MP, intermediate; CA, slow) and the dairy proteins have a superior effect on muscle protein synthesis after exercise compared with SP.

Keywords: caseinate; milk protein; muscle protein synthesis; soy protein; whey protein.

MeSH terms

  • Animals
  • Caseins / chemistry
  • Caseins / pharmacology*
  • Gene Expression Regulation / drug effects
  • Insulin / blood
  • Male
  • Milk Proteins / administration & dosage
  • Milk Proteins / pharmacology*
  • Muscle Proteins / genetics
  • Muscle Proteins / metabolism*
  • Muscle, Skeletal / drug effects*
  • Muscle, Skeletal / metabolism
  • Physical Conditioning, Animal / physiology*
  • Rats
  • Rats, Sprague-Dawley
  • Swimming
  • Whey / administration & dosage*
  • Whey / metabolism


  • Caseins
  • Insulin
  • Milk Proteins
  • Muscle Proteins