ALYSSA M. FENUTA, STUART M. PHILLIPS*
*Corresponding author
McMaster University, Department of Kinesiology, 1280 Main Street West, Hamilton, ON, L8S 4L8, Canada.

Abstract

Sarcopenia is the age-related loss of muscle mass and strength which is subsequently accompanied by reduced functional capacity. Elderly muscle is resistant to anabolic stimuli including resistance exercise and amino acids, in particular leucine. The purpose of this review is to detail the dose-response relationship between dietary protein and muscle protein synthesis (MPS) in older men. The evidence suggests that the muscle of elderly men has a higher protein threshold to stimulate MPS compared to young muscle. At rest, 20 g of whey protein saturated the MPS response, however, combined with resistance exercise, elderly men maximized their MPS response with 40 g of whey protein. The synergistic effect of resistance exercise and ingestion of ~40 g of whey protein would aid in offsetting sarcopenia by augmenting MPS.

INTRODUCTION

Sarcopenia refers to the age-related loss of muscle mass and strength (due in particular to type II muscle fiber loss), which is subsequently accompanied by reduced functional capacity (1). The process begins in the 4th to 5th decade of life, progresses faster in males (2)(~0.6% per year), and is exacerbated with inactivity and inadequate protein consumption (1). For the elderly, some of the consequences of this process include an increased risk of falls and the development of chronic metabolic diseases (e.g. type 2 diabetes) (3). With the world population aged 60 years and older expected to exceed 2 billion by 2050 (1), interventions that effectively offset sarcopenia will help to ensure the maintenance of mobility and subsequently the quality of life in an aging population.
Muscle protein turnover refers to the dynamic equilibrium between protein synthesis and breakdown and represents approximately 25% of whole body protein metabolism (4). Evidence suggests that elderly muscles are resistant to the anabolic stimuli of resistance exercise and amino acids (3). The resulting decrease in MPS rates contributes to an attenuated positive ...