The influence of protein intake on muscle mass and strength in elderly

• Grant number: 17/18769-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2018
• End date: December 31, 2018
• Field of knowledge: Health Sciences - Nutrition - Nutritional Analysis of Population
• Principal Investigator: Hamilton Augusto Roschel da Silva
• Grantee: João Vitor Medeiros Morais
• Host Institution: Escola de Educação Física e Esporte (EEFE). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Ageing is associated with significant declines in muscle mass and strength, which is termed sarcopenia. These reductions occur when rates of muscle protein breakdown are higher than muscle protein synthesis, ensuing a negative net protein balance. Protein intake is one of the most potent stimuli to increase the rate of muscle protein synthesis. In spite of that, older individuals exhibit a reduced muscle protein synthesis in response to anabolic stimuli such as protein intake (i.e., anabolic resistance). In order to overcome sarcopenia, it has been suggested that the dietary protein intake, that is, total quantity, quality, and per meal distribution may influence muscle mass and, consequently, muscle strength in elderly. Thus, the present study aim to investigate the potential association between dietary protein intake considering its total quantity, distribution, source (i.e., animal- vs. plant-based) and the protein quality (i.e., defined by the quantity of essential amino acids and leucine within the main meals of a day) on lower-limb muscle cross sectional area and strength in older individuals. Sixty healthy older individuals, aged above 65 years, of both sexes will be recruit in the present study. Exclusion criteria will be presence of ischemic myocardial disease, arrhythmias, uncontrolled hypertension, type I diabetes, and obesity (body mass index e 30 kg / m²). Muscle mass and strength will be evaluated by magnetic resonance imaging and one-repetition-maximum test, respectively. Dietary records will assess dietary protein intake over three days (two non-consecutives days of the week and one day of the weekend). To investigate the influence of dietary intake (i.e., total quantity) on the dependent variables (i.e., muscle mass and strength) data will be analyzed with a multiple linear regression. Afterwards, the regression model will be adjusted for age, sex, height, protein distribution, source (i.e., animal- vs. plant based) and the protein quality (i.e., defined by the quantity of essential amino acids and leucine within the main meals of a day). It is hypothesized that older individuals with higher dietary protein intake, best distribution and quality of protein will demonstrate greater muscle mass and strength. (AU)