Nutritional Supplements to Support Resistance Exercise in Countering the Sarcopenia of Aging

Abstract

Skeletal muscle plays an indispensable role in metabolic health and physical function. A decrease in muscle mass and function with advancing age exacerbates the likelihood of mobility impairments, disease development, and early mortality. Therefore, the development of non-pharmacological interventions to counteract sarcopenia warrant significant attention. Currently, resistance training provides the most effective, low cost means by which to prevent sarcopenia progression and improve multiple aspects of overall health. Importantly, the impact of resistance training on skeletal muscle mass may be augmented by specific dietary components (i.e., protein), feeding strategies (i.e., timing, per-meal doses of specific macronutrients) and nutritional supplements (e.g., creatine, vitamin-D, omega-3 polyunsaturated fatty acids etc.). The purpose of this review is to provide an up-to-date, evidence-based account of nutritional strategies to enhance resistance training-induced adaptations in an attempt to combat age-related muscle mass loss. In addition, we provide insight on how to incorporate the aforementioned nutritional strategies that may support the growth or maintenance of skeletal muscle and subsequently extend the healthspan of older individuals.

Keywords: aging; diet; exercise; nutrition; protein.

Figure 1

Graphical representation of protein intake throughout the day, with differing total and per-meal protein doses. Sufficient daily protein intake is necessary for an even protein distribution to facilitate reaching the per-meal protein threshold. Blue: older adults’ typical protein intake at each meal based on data from Smeuninx et al. (used with permission) [57]; green: Norton et al. intervention (+0.165 g/kg protein at breakfast- and lunch-time meals) added to typical protein intake reported by Smeuninx et al. [57,90]; orange: even protein distribution pattern with RDA (0.8 g/kg/day); red: even protein distribution pattern with 1.6 g/kg/day based on recommendation from Morton et al. [24]; black line: per-meal protein threshold (0.4 g/kg/meal) to achieve optimal stimulation of MPS for older adults reported by Moore et al. [15].

Figure 2

Schematic illustration of the mechanisms through which the nutritional supplements discussed in the present review may function to promote skeletal muscle adaptation. Leucine has been shown to independently activate the mammalian target of rapamycin (mTOR) signaling pathway through binding to Sestrin2, which increases protein synthesis. Omega-3 polyunsaturated fatty acids (n3-PUFA)—especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—serve as a component of phospholipids in muscle membranes, and not only enhance protein kinase activity, but also improve mitochondrial respiratory sensitivity to ADP. Vitamin D is metabolized to the active form, 1,25(OH)₂D₃, via the liver and kidney, and vitamin D deficiency is associated with impaired skeletal muscle function. Creatine has been shown to enhance resistance exercise performance, which stimulates anabolism through its integral role in the phosphocreatine energy system. Non-steroidal anti-inflammatory drugs (NSAID) reduce inflammation and oxidative stress, which may contribute to muscle loss in older adults. ADP, adenosine di-phosphate; ATP, adenosine tri-phosphate; A, adenosine; P, phosphate; E, energy; COX, cyclo-oxygenase; Leu, leucine; 4EBP1, eukaryotic initiation factor 4E binding protein 1.