Relationship between protein intake and skeletal muscle in older active adults

Abstract

Sarcopenia, loss of skeletal muscle in older adults, can lead to serious health consequences. Several non-pharmacological strategies have been suggested to prevent sarcopenia, one of which is increased protein consumption above the current RDA and/or reaching a certain threshold (≈10 grams of essential amino acids) of quality protein at each meal.PURPOSE: To examine the association between the amount of Skeletal muscle mass in older active adults with regards to their total protein intake and amount of quality protein consumed at each meal throughout the day (quality protein distribution).METHODS: Thirty-three healthy male (n=11) and female (n=22) active older adults (60.1 ± 7.1 years, 168.1 ± 8.4cm, 68.4 ± 12.5kg) participated in this cross sectional study. Total protein (g) and quality protein distribution over 24 hrs (defined as consumption of a meal offering at least 10 grams of EAA) were determined from a seven-day food record. Seven-day food records and subsequent amino acid profiling were analyzed using a computer software program (Nutribase, v.11, Cybersoft Inc., Phoenix, AZ). Daily food records were averaged across seven-days to give an average representation of total protein intake and quality protein distribution. Total and appendicular lean mass were determined by Dual Energy X-Ray Absorptiometry (Discovery A, Hologic Inc., Bedford, MA). Relative lean mass (RLM, total lean mass/height2) and appendicular lean mass (aLM) index (aLM/height2) were calculated. Self-reported physical activity level of the participants was determined using the Godin Leisure-Time Exercise Questionnaire. Data were analyzed using Pearson Partial Correlation Coefficients controlling for body weight and physical activity level with an alpha level of 0.05.RESULTS: Total protein intake (89.9 ± 28.7 g) was positively associated with RLM (r = 0.598, p = 0.001) as well as aLM index (r = 0.605, p < 0.001). Quality protein distribution throughout a day (1.02 ± 0.60) was also positively associated with RLM (r = 0.502, p = 0.005) and aLM index (r = 0.464, p = 0.01).CONCLUSIONS: Our data suggest that, not only total protein, but also the quality and quantity (≈10 grams of essential amino acids) of protein consumed throughout a day may be important for maintaining muscle mass in older adults.