Friday, April 20, 2012

Age-related Changes In muscle protein synthesis by Jerry Brainum

Several studies have shown that older people experience a decreased rate of muscle protein synthesis. A study presented at the ’06 ACSM meeting compared the changes in plasma amino acid concentrations and muscle protein synthesis rates in healthy young and older subjects following a meal that included four ounces of lean beef.1

The younger subjects’ average age was 28; the older subjects, 69. The authors calculated the rate of muscle protein synthesis immediately following and for five hours after the beef meal. Eating beef increased MPS rates in both the young (27.9 percent) and older (29.1 percent) subjects. The plasma amino acid levels peaked about 100 minutes after the meal in both groups. The magnitude of increase in blood amino acid levels was higher in the older group because of smaller blood volume and lower lean mass.

The study shows the fate of ingested food protein in both young and older people, which proved to be similar. Another useful observation involved the peak amino acid level, which occurred about 1 1/2 hours after subjects in both groups ate the meal.

Another study presented at the meeting involved providing carbohydrate with or without protein and free leucine (a branched-chain amino acid) to young and older groups, again to compare rates of protein balance and muscle protein synthesis.2 As expected, insulin levels rose higher in both groups when they got a carb-protein-and-leucine supplement. Carbs alone provided no increases in MPS. The researchers’ conclusion was that combining carbs, protein and leucine brought about similar rates of upgraded MPS in both the young and old.


1 Paddon-Jones, D., et al. (2006). Age specific changes in protein synthesis and plasma amino acid profiles following intact protein ingestion. Med Sci Sports Exerc. 38:S113.

2 Koopman, R.,et al. (2006). Co-ingestion of protein and leucine stimulates muscle protein synthesis in young and elderly men. Med Sci Sports Exer. 38:S113.

©,2012, Jerry Brainum.Any reprinting in any type of media, including electronic and foreign is expressly prohibited