Enhancing Muscle Quality: Exploring Leucine and Whey Protein in Sarcopenic Individuals

Abstract

Background: Sarcopenia is characterised by a decline in the skeletal muscle mass with increasing age. This poses many challenges to the health and independence of older individuals. New and emerging studies have focused on supplementing leucine-enriched whey protein and resistance training in older adults to mitigate the effects of sarcopenia, including significant muscle mass loss.

Methods: This study aimed to comprehensively analyse the current literature regarding the beneficial effects of leucine-enriched whey protein supplementation in older adults. This article systematically reviewed randomised controlled trials, longitudinal studies, and meta-analyses published between 2011 and 2024. The biochemical mechanisms underlying the anabolic properties of leucine, including its role in protein synthesis and mTOR signalling pathways, were explored to elucidate its potential to enhance muscle protein accretion.

Results: Findings from the reviewed studies indicate that the combined intervention of leucine-enriched whey protein supplementation and resistance training elicits favourable outcomes regarding increased lean muscle mass, muscle strength and physical performance in older adults with sarcopenia. The potential of leucine-enriched whey protein to mitigate muscle protein breakdown is discussed along with its potential synergistic effects with resistance exercise to optimise muscle adaptation. Future research directions, including investigations of optimal dosing regimens, long-term sustainability and potential contraindications, are proposed to enhance the precision and applicability of this intervention strategy.

Conclusion: Leucine-enriched whey protein supplementation combined with resistance training is beneficial in addressing sarcopenia in older adults. This review consolidates the current understanding of this intervention, highlights its potential benefits and provides insights for future research and clinical applications in geriatric muscle health.

Keywords: mTOR signalling pathway; muscle health; whey protein.

FIGURE 1

Sarcopenia in cancer patients.

FIGURE 2

mTOR signalling pathway. Following is the summary of the mTOR signalling pathway in skeletal muscle. This pathway is affected by multiple factors, and it is activated by insulin, mechanical stimulation and amino acids, which are represented by blue line. It is inhibited by glucocorticoids and myostatin, which is represented by orange lines [18].

FIGURE 3

Sirtuin pathway and pathophysiology of sarcopenia. IL‐6 = interleukin‐6, SIRT1 = sirtuin 1, CRP = C‐reactive protein, FOXO = fork head box transcription, NOX4 = NADPH oxidase 4, IkB = IkappaB kinase, MnSOD = superoxide dismutase 2, PGC‐1α = peroxisome proliferator‐activated receptor gamma coactivator, IDH2 = isocitrate dehydrogenase 2, Nrf1 = nuclear respiratory factor, Gpx1 = glutathione peroxidase 1.

FIGURE 4

Role of resistance training in sarcopenia.

FIGURE 5

Individuals at risk, symptoms and treatment of sarcopenia.

FIGURE 6

Types of resistance exercises for older adults to do at home.

FIGURE 7

Different mechanisms involving whey protein and leucine as immune nutrients. Whey protein induces protein breakdown and synthesis in muscles, influences lipid metabolism and affects the antioxidant system. Ca²⁺ = calcium, 1,25‐(OH)₂ = 1,25‐hydroxycholecalciferol, [Ca²⁺] = intracellular calcium concentration, TGs = triacylglycerol [35].