Milk for Skeletal Muscle Health and Sarcopenia in Older Adults: A Narrative Review

Abstract

Skeletal muscle aging manifests as a decline in muscle quantity and quality that accelerates with aging, increasing the risk of sarcopenia. Sarcopenia is characterized by a loss of muscle strength and mass, and contributes to adverse health outcomes in older adults. Intervention studies have shown that sarcopenia may be treated by higher protein intake in combination with resistance exercise (RE). In comparison, less is known about the role of whole protein-containing foods in preventing or treating sarcopenia. Liquid milk contains multiple nutrients and bioactive components that may be beneficial for muscle, including proteins for muscle anabolism that, alone or with RE, may have myoprotective properties. However, there is a lack of evidence about the role of milk and its effects on muscle aging. This narrative review considers evidence from three observational and eight intervention studies that used milk or fortified milk, with or without exercise, as an intervention to promote muscle health and function in older adults (aged 50-99 years). The observational studies showed no association between higher habitual milk consumption and muscle-related outcomes. The results of intervention studies using fortified milk in relation to elements of sarcopenia were also negative, with further inconclusive results from the studies using a combination of (fortified) milk and exercise. Although milk contains nutrients that may be myoprotective, current evidence does not show beneficial effects of milk on muscle health in older adults. This could be due to high habitual protein intakes (>1.0 g/kg BW/d) in study participants, differences in the type of milk (low-fat vs whole) and timing of milk consumption, length of interventions, as well as differences in the sarcopenia status of participants in trials. Adequately powered intervention studies of individuals likely to benefit are needed to test the effectiveness of a whole food approach, including milk, for healthy muscle aging.

Keywords: milk; muscle health; myoprotective properties; older adults; sarcopenia; whole foods.

Figure 1

Hypothesized myoprotective properties of nutrients in liquid milk. Notes: Hypothesized health effects and function of milk nutrients and bioactive components on muscle may include energy, minerals and vitamin delivery, anabolic, anti-oxidative, anti-inflammatory, and immunomodulatory pathways. Common pathways across the nutrients and non-nutrients are presented in the outer circle in white. © Newcastle University. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License https://creativecommons.org/licenses/by-nc-sa/3.0/. Abbreviations: EAA, essential amino acids; MFGM, milk fat globule membrane; MPS, muscle protein synthesis.