Effect of protein source on resistive-training-induced changes in body composition and muscle size in older men.
BACKGROUND
Aging is associated with reductions in muscle mass and strength, but nutrition and exercise interventions can delay this progression and enhance the quality of life.


OBJECTIVE
We examined whether the predominant source of protein consumed by older men influenced measures of muscle size and strength, body composition, resting energy expenditure, and skeletal muscle creatine concentrations in response to 12 wk of resistive training.


METHODS
After consuming a lactoovovegetarian (LOV) diet for 2 wk, 21 men aged 65 +/- 5 y were randomly assigned to either consume a beef-containing (BC) diet (n = 10) or to continue the LOV diet (n = 11) throughout resistive training. The BC diet included 0.6 g protein. kg(-1). d(-1) from beef and the LOV diet included 0.6 g protein. kg(-1). d(-1) from textured vegetable protein (soy) sources. The remaining protein in the diets came from self-selected LOV sources.


RESULTS
The mean total protein intake for both groups ranged from 1.03 to 1.17 g. kg(-1). d(-1) during the intervention. Men in both groups had improvements (14-38%) in maximal dynamic strength of all the muscle groups trained with no significant difference between groups. With resistive training, cross-sectional muscle area of the vastus lateralis increased in both groups (4.2 +/- 3.0% and 6.0 +/- 2.6% for the LOV and BC groups, respectively) with no significant difference between groups. Body composition, resting energy expenditure, and concentrations of muscle creatine, phosphocreatine, and total creatine did not differ significantly between groups or change over time.


CONCLUSIONS
These data suggest that increases in muscle strength and size were not influenced by the predominant source of protein consumed by older men with adequate total protein intake.
Department of Human Nutrition, Kansas State University, Manhattan, KS 66506, USA. haub@humec.ksu.edu
Mark D
MD
Haub
Amanda M
AM
Wells
Mark A
MA
Tarnopolsky
Wayne W
WW
Campbell
D000368:Aged; D000375:Aging; D000818:Animals; D001481:Basal Metabolism; D001823:Body Composition; D002417:Cattle; D014676:Diet, Vegetarian; D004044:Dietary Proteins / Q000008:administration & dosage*; D004734:Energy Metabolism; D015444:Exercise; D006801:Humans; D008297:Male; D008460:Meat; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology; D030262:Soybean Proteins / Q000008:administration & dosage
D004044:Dietary Proteins; D030262:Soybean Proteins