Protein Intake and Frailty: A Matter of Quantity, Quality, and Timing

Abstract

Frailty is a geriatric syndrome that refers to a state of reduced resiliency to stressful events that occurs in response to physiological and/or psychosocial detriments. Frailty is a predictor of poor prognosis, given that frail older adults are at higher risk of many adverse health-related events. Hence, the identification of potential strategies to prevent the development and progression of frailty is of extreme importance for avoiding its negative outcomes. An adequate protein consumption is advocated as a possible intervention for the management of frailty in older adults due to its effects on muscle mass and physical function. However, empirical evidence is still needed to support this proposition. On the other hand, substantial evidence from observational studies has provided important information on the association between frailty and dietary protein-related parameters. Here, we provide a narrative review of the current literature regarding the association between protein intake (amount (how much?), quality (what type?), and distribution across meals (when?)) and frailty-related parameters. The ultimate aim of this work is to offer practical, evidence-based indications to healthcare professionals responsible for the care of frail older adults.

Keywords: aging; amino acids; diet; dietary patterns; disability; metabolism; nutrition; physical function; protein per meal; sarcopenia.

Figure 1

Protein absorption and digestion. Abbreviations: AA, amino acid; HCl, hydrochloric acid; P, protein.

Figure 2

Anabolic resistance to protein intake in older adults. Abbreviation: AA, amino acid.

Figure 3

Sarcopenia and frailty.

Figure 4

Animal- and plant-based protein sources. Animal-based plant protein is expected to have a higher content of branched-chain amino acids (BCAAs), thereby evoking greater stimulation of anabolic pathways and muscle protein synthesis than plant-based protein.