Do protein and leucine supplements stimulate muscle protein synthesis rates to the same extent in young and elderly lean men?

From: The American Journal of Clinical Nutrition

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  • Eight elderly (mean age 75) and 8 young (mean age 20) lean men


  • Participants were randomly assigned to consume either carbohydrate, or carbohydrate plus protein and free leucine after performing 30 min of activities of daily living.
  • The subjects received a beverage volume of 1.33 mL/kg every 30 min to ensure a given dose of 0.49 g carbohydrate/kg (50% as glucose and 50% as maltodextrin) with or without the addition of 0.16 g/kg of a whey protein hydrolysate and 0.03 g/kg leucine every hour.
  • Blood and muscle samples were collected to assess whole-body protein turnover and the protein fractional synthetic rate in the vastus lateralis muscle over a 6-h period.


  • Whole-body phenylalanine and tyrosine (amino acids) were significantly higher in the young than in the elderly men.
  • Protein balance was negative in the carbohydrate experiment but positive in the carbohydrate plus protein plus leucine experiment in both groups.
  • Mixed-muscle protein synthesis rates were significantly greater in the carbohydrate plus protein plus leucine than in the carbohydrate experiment in both the young and the elderly subjects, with no significant differences between groups.


  • Yes (with confidence) – with co-ingestion of carbohydrate plus protein plus leucine


Editors Notes

  • Ageing is associated with a slow, progressive loss of skeletal muscle mass, which is also called sarcopenia.
  • Sarcopenia is generally accompanied by a reduction in strength, the loss of functional capacity, and an increased risk of developing chronic metabolic diseases such as obesity, type 2 diabetes, and osteoporosis.
  • Sarcopenia is facilitated by a combination of factors, which include a sedentary lifestyle and a less-than-optimal diet