<p>Milk for Skeletal Muscle Health and Sarcopenia in Older Adults: A Narrative Review</p>

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.

Myoprotective Whole Foods, Muscle Health and Sarcopenia: A Systematic Review of Observational and Intervention Studies in Older Adults

“…Current evidence implicates modifiable lifestyle factors, diet and exercise, as non-pharmacological treatments for poor muscle health and sarcopenia [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], implemented either alone [ 10 , 12 , 13 , 15 ] or in combination [ 9 , 11 ]. Several approaches have been utilised to investigate the diet-muscle relationship with ageing, employing either a single nutrient [ 9 , 10 , 11 , 12 , 13 ], whole food [ 14 , 15 , 16 ], or whole diet approach [ 17 , 18 ], whilst resistance exercise (RE) has been recognised as a powerful stimulus for muscle anabolism in older adults [ 19 ]. Specifically, interventions with protein supplements and RE have been effective in ameliorating the decline in muscle mass and function in older adults with and without sarcopenia and frailty [ 7 , 10 ].…”

“…A body of research has focused on the role of individual whole foods rich in nutrients hypothesised to be beneficial for muscle (myoprotective), such as protein-rich whole foods, to establish the role of protein source (quality), quantity, and timing of intake in muscle ageing [ 14 , 15 ]. Others have evaluated the influence of selected foods in the context of whole diet to understand their individual contribution to muscle health and function [ 17 , 18 ], and the potential cumulative and synergistic benefits of nutrients and non-nutrients in these foods for muscle [ 16 ]. To our knowledge, a systematic evaluation of the studies that used a whole food approach in relation to muscle health and sarcopenia in older adults is lacking.…”

“…To our knowledge, a systematic evaluation of the studies that used a whole food approach in relation to muscle health and sarcopenia in older adults is lacking. We have recently found limited evidence for the role of liquid milk in muscle health in older adults, that has potential to have beneficial effects, acting through anabolic, anti-oxidative, anti-inflammatory, and immunomodulating pathways implicated in sarcopenia [ 16 ]. To examine further whether other whole foods rich in specific nutrients influence muscle health, we aimed to summarise evidence from observational and intervention studies that used meat, fish, eggs, fruit and vegetables, and non-liquid dairy (yoghurt and cheese) in relation to muscle mass, function, and sarcopenia in older adults aged 50 and over.…”

Dairy Consumption and Metabolic Health

“…Evidence from prospective cohort studies suggests that moderate milk consumption compared to none or low intakes during pregnancy is positively associated with foetal growth and infant birth weight in healthy, Western populations [ 16 ]. Finally, several studies point to the benefits of milk and dairy products in diets of the elderly and highlight that, in combination with physical activity, milk and dairy products can improve muscle mass and function resulting in a lower risk of sarcopenia and vertebral fractures [ 16 ], although another recent review of the area did not find strong evidence for a benefit of milk on muscle health in older adults [ 17 ].…”

Feasibility and acceptability of a milk and resistance exercise intervention to improve muscle function in community-dwelling older adults (MIlkMAN): Pilot study

“…Cow's milk can be an important part of a healthy diet and a source of several essential nutrients, including high-quality proteins such as whey (a rich source of branched-chain amino acid leucine (5.6 g per 25 g of whey protein [13]), the main dietary regulator of muscle protein synthesis (MPS)), bioactive lipids and fatty acids, minerals, and vitamins [14], which synergistically may be beneficial for skeletal muscle (discussed in Granic et al 2020 [15]). In addition, the benefit of milk proteins is thought to come from the higher essential amino acid (EAA) score, bioavailability and solubility compared with other animal and plant protein sources [16].…”