Dietary protein considerations for muscle protein synthesis and muscle mass preservation in older adults

Abstract

Amino acid (AA) bioavailability is critical for muscle protein synthesis (MPS) and preservation of skeletal muscle mass (SMM). Ageing is associated with reduced responsiveness of MPS to essential amino acids (EAAs). Further, the older population experience anabolic resistance, leading to increased frailty, functional decline and depleted muscle mass preservation, which facilitates the need for increased protein intake to increase their SMM. This review focuses on the role of proteins in muscle mass preservation and examines the contribution of EAAs and protein intake patterns to MPS. Leucine is the most widely studied AA for its role as a potent stimulator of MPS, though due to inadequate data little is yet known about the role of other EAAs. Reaching a conclusion on the best pattern of protein intake has proven difficult due to conflicting studies. A mixture of animal and plant proteins can contribute to increased MPS and potentially attenuate muscle wasting conditions, however there is limited research on the biological impact of protein blends in older adults. While there is some evidence to suggest that liquid protein foods with higher than the recommended daily allowance (RDA) of protein may be the best strategy for achieving high MPS rates in older adults, clinical trials are warranted to confirm an association between food form and SMM preservation. Further research is warranted before adequate recommendations and strategies for optimising SMM in the elderly population can be proposed.

How to Overcome Anabolic Resistance in Dialysis-Treated Patients?

“…They observed that a 20-g dose of whey protein (containing ~10 g essential AAs) is sufficient for the maximal stimulation of MPS both at rest and during physical exercise, while a greater dose stimulates amino acid oxidation. However, in elderly subjects, more protein with respect to younger subjects is needed to maximally stimulate MPS in exercised and rested muscle ( 15 ).…”

Dietary protein interventions to improve nutritional status in end-stage renal disease patients undergoing hemodialysis

“…In healthy young adults, ingestion of 20 g high-quality protein has been shown to maximize postprandial muscle protein synthesis rates [ 10 ]. In older adults, the muscle protein synthetic response following such an amount of protein ingestion is attenuated when compared with younger adults, a phenomenon that has been coined anabolic resistance [ 11 ]. Recently, van Vliet et al [ 12 ▪▪ ] reported that in CHD patients, ingestion of a mixed-meal containing 20 g intrinsically labeled protein on a nondialysis day failed to increase skeletal muscle protein synthesis rates.…”

“…In healthy older adults, it has been shown that due to anabolic resistance ingestion of ∼35 g protein is required to maximize postprandial muscle protein synthesis rates [ 11 ]. Yet, in CHD patients, the ingestion of such large amounts of protein would also represent a high phosphate intake.…”

Dietary Essential Amino Acid Intake Is Associated with High Muscle Strength in Korean Older Adults

“…Age-related muscle weakening can be reduced by adequate protein intake [ 4 ]. However, in Korea, the protein intake is much lower in older adults aged ≥65 years than in other age groups; specifically, the number of people with inadequate animal protein intake is rising [ 5 ].…”