Dietary protein requirements and recommendations for healthy older adults: a critical narrative review of the scientific evidence

Abstract

Adequate protein intake is essential for the maintenance of whole-body protein mass. Different methodological approaches are used to substantiate the evidence for the current protein recommendation, and it is continuously debated whether older adults require more protein to counteract the age-dependent loss of muscle mass, sarcopenia. Thus, the purpose of this critical narrative review is to outline and discuss differences in the approaches and methodologies assessing the protein requirements and hence, resulting in controversies in current protein recommendations for healthy older adults. Through a literature search, this narrative review first summarizes the historical development of the FAO/WHO/UNU setting of protein requirements and recommendations for healthy older adults. Hereafter, we describe the various types of studies (epidemiological studies and protein turnover kinetic measurements) and applied methodological approaches founding the basis and the different recommendations with focus on healthy older adults. Finally, we discuss important factors to be considered in future studies to create evidence for international agreement on protein requirements and recommendations for healthy older adults. We conclude by proposing future directions to determine “true” protein requirement and recommendation for healthy older adults.

The role of nutrition in the prevention of sarcopenia

“…Nishimura et al. [ 28 ] argue that recommendations to increase protein intakes are extrapolated from the findings of acute feeding studies and that there are potential limitations to using these data to set whole-body protein requirements, which could have important implications for policymakers setting population recommendations. The recent systematic review by Hengeveld et al.…”

“…The macronutrient most extensively researched in relation to sarcopenia is protein, as it is an anabolic stimulus that increases muscle protein synthesis after feeding, as well as a source of amino acids [ 27 ]. There is some evidence that anabolic responses to feeding are blunted among older adults, suggesting that higher protein intakes are needed in older age to preserve muscle mass and function [ 28 ], particularly in combination with exercise training [ 29 ]. However, the role of differences in habitual diets, and whether protein intakes below recommended levels in older age contribute to imbalances in protein metabolism and accelerated losses of skeletal muscle mass and function, continue to be topics of debate [ 15 , 28 ].…”

Myoprotective whole foods, muscle health and sarcopenia in older adults

“…Adequate consumption of protein-rich foods may help to combat imbalance between muscle protein synthesis (MPS) and breakdown with ageing [15], especially foods providing high-quality proteins with higher content of essential amino acids (EAA) such as leucine. Protein-rich foods that have a high Digestible Indispensable Amino Acid Score (≥75), a metric used to evaluate the protein quality in a food, meal, or diet, come from both animal and plant sources.…”

Co-ingestion of cluster dextrin carbohydrate does not increase exogenous protein-derived amino acid release or myofibrillar protein synthesis following a whole-body resistance exercise in moderately trained younger males: a double-blinded randomized controlled crossover trial

“…This is due to a decrease in the rate of digestion and absorption [16] and an increase in the retention of amino acids in the portal drained viscera [20]. In addition, amino acid availability in the circulation is reduced by suppression of protein breakdown [21,22]. Although plasma insulin concentration was greater when protein was ingested with carbohydrate [15][16][17] or a mixed meal [18], muscle protein synthesis was not augmented as compared to protein intake alone [15][16][17].…”