Protein and amino acid supplementation in older humans

Towards Healthy Longevity: Comprehensive Insights from Molecular Targets and Biomarkers to Biological Clocks

Aging is a complex and time-dependent decline in physiological function that affects most organisms, leading to increased risk of age-related diseases. Investigating the molecular underpinnings of aging is crucial to identify geroprotectors, precisely quantify biological age, and propose healthy longevity approaches. This review explores pathways that are currently being investigated as intervention targets and aging biomarkers spanning molecular, cellular, and systemic dimensions. Interventions that target these hallmarks may ameliorate the aging process, with some progressing to clinical trials. Biomarkers of these hallmarks are used to estimate biological aging and risk of aging-associated disease. Utilizing aging biomarkers, biological aging clocks can be constructed that predict a state of abnormal aging, age-related diseases, and increased mortality. Biological age estimation can therefore provide the basis for a fine-grained risk stratification by predicting all-cause mortality well ahead of the onset of specific diseases, thus offering a window for intervention. Yet, despite technological advancements, challenges persist due to individual variability and the dynamic nature of these biomarkers. Addressing this requires longitudinal studies for robust biomarker identification. Overall, utilizing the hallmarks of aging to discover new drug targets and develop new biomarkers opens new frontiers in medicine. Prospects involve multi-omics integration, machine learning, and personalized approaches for targeted interventions, promising a healthier aging population.

Protein and Exercise to Reverse Frailty in Older Men and Women Undergoing Transcatheter Aortic Valve Replacement: Design of the PERFORM-TAVR Trial

Despite the high procedural success of transcatheter aortic valve replacement (TAVR), 2 out of 5 older adults report poor physical performance and health-related quality of life (HRQOL) in the ensuing months, particularly those with frailty. There has yet to be a trial examining the synergistic effects of exercise and protein supplementation to counteract frailty and improve patient-centred outcomes following TAVR. The PERFORM-TAVR trial is a multicentre parallel-group randomised clinical trial that is enrolling 200 frail older adults ≥ 70 years of age undergoing TAVR. Patients will be randomly allocated to 1 of 2 treatment groups: standard-of-care lifestyle education (control group) or protein-rich oral nutritional supplement for 4 weeks before TAVR with the addition of home-based supervised exercise sessions for 12 weeks after TAVR (intervention group). The primary outcome will be physical performance as measured by a blinded observer using the Short Physical Performance Battery at 3 months. Secondary outcomes at 3, 6, and 12 months will include HRQOL, as measured by the Short-Form 36 Physical and Mental Component summary scores, and a composite safety end point. The PERFORM-TAVR trial is testing a novel frailty intervention in older adults undergoing TAVR to optimise recovery and downstream HRQOL. This represents a potential paradigm shift that highlights the value of assessing and treating patients' frailty in parallel with their underlying heart valve disease. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT03522454.

Nitric Oxide as a Determinant of Human Longevity and Health Span

The master molecular regulators and mechanisms determining longevity and health span include nitric oxide (NO) and superoxide anion radicals (SOR). L-arginine, the NO synthase (NOS) substrate, can restore a healthy ratio between the dangerous SOR and the protective NO radical to promote healthy aging. Antioxidant supplementation orchestrates protection against oxidative stress and damage-L-arginine and antioxidants such as vitamin C increase NO production and bioavailability. Uncoupling of NO generation with the appearance of SOR can be induced by asymmetric dimethylarginine (ADMA). L-arginine can displace ADMA from the site of NO formation if sufficient amounts of the amino acid are available. Antioxidants such as ascorbic acids can scavenge SOR and increase the bioavailability of NO. The topics of this review are the complex interactions of antioxidant agents with L-arginine, which determine NO bioactivity and protection against age-related degeneration.

Mitigating Sarcopenia with Diet and Exercise

Sarcopenia is the loss of muscle mass and function from aging, inactivity, or disuse. It is a comorbidity to numerous conditions that exacerbates their severity and adversely impacts activities of daily living. While sarcopenia now receives more attention from the medical community, people with sarcopenia as a comorbidity nevertheless still sometimes receives less attention than other presenting diseases or conditions. Inevitable doctors' visits or hospital stays for those with sarcopenia as a comorbidity have far higher healthcare costs than those without this condition, which imposes a greater financial burden on the medical insurance and healthcare industries. This review offers information and guidance on this topic. Treatments for sarcopenia include dietary, exercise, and pharmacological interventions. Yet, the latter treatment is only recommended in extreme cases as it may evoke numerous side effects and has little support in the scientific literature. Currently, a more holistic approach, with an emphasis on lifestyle modification, to reduce the likelihood of sarcopenia is examined. The current review discusses dietary and exercise interventions to limit the occurrence and severity of sarcopenia. References cited in this review conformed to the Declaration of Helsinki requirements for the use of human research subjects. Most of this review's references (~97%) came from a PubMed search that spanned from 1997 to 2023. Search terms included "sarcopenia" OR "muscle wasting" OR "geriatrics"; OR "ageing"; and AND "diet" OR "exercise". In addition, papers relevant or supportive of the topic as well as those considered seminal were included in the review. Over 96% of the references were peer-reviewed articles.

A Transcriptomic Regulatory Network among miRNAs, lncRNAs, circRNAs, and mRNAs Associated with L-leucine-induced Proliferation of Equine Satellite Cells

In response to muscle injury, muscle stem cells are stimulated by environmental signals to integrate into damaged tissue to mediate regeneration. L-leucine (L-leu), a branched-chain amino acid (BCAA) that belongs to the essential amino acids (AAs) of the animal, has gained global interest on account of its muscle-building and regenerating effects. The present study was designed to investigate the impact of L-leu exposure to promote the proliferation of equine skeletal muscle satellite cells (SCs) on the regulation of RNA networks, including mRNA, long non-coding RNA (lncRNA), covalently closed circular RNA (circRNA), and microRNA (miRNA) in skeletal muscles. Equine SCs were used as a cell model and cultured in different concentrations of L-leu medium. The cell proliferation assay found that the optimal concentration of L-leu was 2 mM, so we selected cells cultured with L-leu concentrations of 0 mM and 2 mM for whole-transcriptiome sequencing, respectively. By high-throughput sequencing analysis, 2470 differentially expressed mRNAs (dif-mRNAs), 363 differentially expressed lncRNAs (dif-lncRNAs), 634 differentially expressed circRNAs (dif-circRNAs), and 49 differentially expressed miRNAs (dif-miRNAs) were significantly altered in equine SCs treated with L-leu. To identify the function of autoimmunity and anti-inflammatory responses after L-leu exposure, enrichment analysis was conducted on those differentially expressed genes (DEGs) related to lncRNA, circRNA, and miRNA. The hub genes were selected from PPI Network, including ACACB, HMGCR, IDI1, HAO1, SHMT2, PSPH, PSAT1, ASS1, PHGDH, MTHFD2, and DPYD, and were further identified as candidate biomarkers to regulate the L-leu-induced proliferation of equine SCs. The up-regulated novel 699_star, down-regulated novel 170_star, and novel 360_mature were significantly involved in the competing endogenous RNA (ceRNA) complex network. The hub genes involved in cell metabolism and dif-miRNAs may play fundamental roles in the L-leu-induced proliferation of equine SCs. Our findings suggested that the potential network regulation of miRNAs, circ-RNAs, lncRNAs, and mRNAs plays an important role in the proliferation of equine SCs, so as to build up new perspectives on improving equine performance and treatment strategies for the muscle injuries of horses.

Protein and Energy Supplements for the Elderly

The proportion of elderly individuals is rising globally, and data have shown that as high as 8% of the elderly community suffer from malnutrition. Protein energy malnutrition has shown to elevate morbidity and mortality risk in the elderly; therefore, protein and energy supplement are needed for the elderly populations to create healthy conditions. This chapter describes about general structure of protein, protein turnover, amino acid metabolism including metabolism in the elderly, protein change in aging, supplementation of amino acid as well as vitamin and mineral for the elderly. The discussion in this section aims to provide a general description of protein, amino acids, changes in amino acid metabolism in the elderly, and the benefits of supplementing amino acids as well as vitamins and minerals for the elderly.

Lipid and metabolite correlation networks specific to clinical and biochemical covariate show differences associated with sexual dimorphism in a cohort of nonagenarians

This study defines and estimates the metabolite-lipidic component association networks constructed from an array of 20 metabolites and 114 lipids identified and quantified via NMR spectroscopy in the serum of a cohort of 355 Italian nonagenarians and ultra-nonagenarian. Metabolite-lipid association networks were built for men and women and related to an array of 101 clinical and biochemical parameters, including the presence of diseases, bio-humoral parameters, familiarity diseases, drugs treatments, and risk factors. Different connectivity patterns were observed in lipids, branched chains amino acids, alanine, and ketone bodies, suggesting their association with the sex-related and sex-clinical condition-related intrinsic metabolic changes. Furthermore, our results demonstrate, using a holistic system biology approach, that the characterization of metabolic structures and their dynamic inter-connections is a promising tool to shed light on the dimorphic pathophysiological mechanisms of aging at the molecular level.

International Regulations on Amino Acid Use in Foods and Supplements and Recommendations to Control Their Safety Based on Purity and Quality

We examined international regulatory developments related to the use of proteinogenic amino acids in human nutrition and concluded that the current risk-assessment practices tend to focus exclusively on setting maximum daily limits. In this brief review we argue that controlling the standards of purity and ingredient quality are the key safety issues that should be considered during risk assessment. Moreover, if maximum intake limits on amino acids are implemented, they should be defined using a well-established rationale for the health risks associated with high intakes. This would avoid setting limits that are so low that they render the dietary supplements ineffective and which, therefore, could mislead the consumer. We further suggest that there should be greater regional concordance in how the use of amino acids as ingredients is regulated and use the capacity of industry to oversee pre-competitive issues, such as standards of purity and scientific research on the safety of generic ingredients. Our arguments are based on clinical safety scientific research and oversights of amino acid purity standards conducted in the last decade by the not-for-profit international association, the International Council on Amino Acid Science.

Utilization of Hydroxyl-Methyl Butyrate, Leucine, Glutamine and Arginine Supplementation in Nutritional Management of Sarcopenia-Implications and Clinical Considerations for Type 2 Diabetes Mellitus Risk Modulation

While onset characteristics may vary, sarcopenia gradually develops over time as a result of the aging process, leading to muscle loss, disturbance of the muscle to fat ratio, and a variety of negative symptoms undermining the wellbeing, quality of life, and lifespan in the aging population globally. There is evidence that sarcopenia may be a cause and consequence of type 2 diabetes mellitus (T2DM) in the aging population. The importance of nutritional management in the prevention and/or deceleration of sarcopenia is critical, with the main focus placed on the amount and quality of protein intake. Significant efforts are being made towards the development of medical nutrition therapies involving certain amino acids and amino compounds, as well as their combinations, for the improvement in muscle strength, muscle function and protein synthesis. This may reduce hospitalization times and hasten the recovery of patients with sarcopenia. The administration of protocols with varying dose and frequencies, as well as their efficacy, is being investigated. In the work herein, we present and evaluate data derived from human trials regarding the utilization of hydroxyl-methyl butyrate (HMB), L-leucine (Leu), L-glutamine (Gln) and L-arginine (Arg) supplementation for optimal management of sarcopenia in geriatric patients, a topic of significant clinical nutrition interest which may have important implications in T2DM status.

Dietary strategies for mitigating osteosarcopenia in older adults: a narrative review

The synchronic loss of bone mineral density and decrease in muscle mass, strength, and function defines the scenario of osteosarcopenia, which is associated with an increased risk of falls and fractures in older adults. An important role in preventing muscle and bone loss is played by nutritional factors, in particular the intake of proteins, calcium, magnesium and vitamin D. This review summarizes the available literature concerning the influence of protein intake and supplementation (vitamin D, Ca, Mg, branched-chain amino acids) on the decline of musculoskeletal integrity in healthy older adults. Furthermore, in this paper, we attempted to give some suggestions to build up adequate nutritional and dietary strategies against the age-related loss of muscle and bone mass.

The Asia-Pacific Clinical Practice Guidelines for the Management of Frailty

OBJECTIVE

To develop Clinical Practice Guidelines for the screening, assessment and management of the geriatric condition of frailty.

METHODS

An adapted Grading of Recommendations, Assessment, Development, and Evaluation approach was used to develop the guidelines. This process involved detailed evaluation of the current scientific evidence paired with expert panel interpretation. Three categories of Clinical Practice Guidelines recommendations were developed: strong, conditional, and no recommendation.

RECOMMENDATIONS

Strong recommendations were (1) use a validated measurement tool to identify frailty; (2) prescribe physical activity with a resistance training component; and (3) address polypharmacy by reducing or deprescribing any inappropriate/superfluous medications. Conditional recommendations were (1) screen for, and address modifiable causes of fatigue; (2) for persons exhibiting unintentional weight loss, screen for reversible causes and consider food fortification and protein/caloric supplementation; and (3) prescribe vitamin D for individuals deficient in vitamin D. No recommendation was given regarding the provision of a patient support and education plan.

CONCLUSIONS

The recommendations provided herein are intended for use by healthcare providers in their management of older adults with frailty in the Asia Pacific region. It is proposed that regional guideline support committees be formed to help provide regular updates to these evidence-based guidelines.

Protein and exercise in the prevention of sarcopenia and aging

Aging is associated with a progressive decline in skeletal muscle mass and strength. The decline, known as sarcopenia, could lead to physical disability, poor quality of life, and death. In addition, the older population usually experiences age-related muscle changes that affect muscle mass, muscular strength, and functional abilities. The purpose of this review is to describe the role of protein and exercise in slowing the progression of sarcopenia. It will also discuss whether age-related changes can be attenuated by dietary protein and exercise in the older population. This review will also cover one of the possible mechanisms of how dietary protein and exercise are involved in sarcopenia prevention, as well as the available measurement tools. Based on the findings of this review, the adequate amount of protein required for older men and women needs to be revised and likely be higher. Moreover, studies are required to explore some inconclusive findings concerning sarcopenia in the older population. Further research is required to investigate the following: (1) the safety and effectiveness concerning the consumption of 1.4 g of protein/kg of body weight (or more) in this vulnerable population; (2) the effectiveness of amino acid supplementation in reducing progression of sarcopenia over time through longitudinal studies; (3) the preferred source and timing of protein for the older population to maintain muscular strength and attenuate sarcopenia; (4) exercise interventions, especially those of longer duration, in the attenuation of sarcopenia; (5) other types of exercise and their effects on age-related muscle changes; (6) the mechanism of how protein and exercise prevent muscle loss with aging; and (7) determine the best method to diagnose sarcopenia.

Safety and Tolerability of Leucine Supplementation in Elderly Men

Leucine, a branched-chain amino acid, has been shown to stimulate muscle protein synthesis and has been suggested to play a role in the prevention of age-related muscle atrophy (sarcopenia). Although leucine supplementation may be beneficial, the efficacious dose of leucine is unknown. Before conducting studies with increased doses of leucine, the Tolerable Upper Intake Level (UL) for leucine needs to be determined. The objective of this review is to describe 2 current studies to determine the UL for leucine in young and elderly men. Initially, in young men we tested the conceptual model of determining the maximum oxidative capacity of an amino acid to be an ideal marker for identifying the UL. Leucine oxidation, measured with the use of l-[1-¹³C]leucine, increased with increasing leucine intakes and reached a plateau at higher intakes. Two-phase linear regression analysis identified a breakpoint of 550 mg ⋅ kg^-1 ⋅ d^-1 (95% CI: 454, 646 mg ⋅ kg^-1 ⋅ d^-1), with a simultaneous increase in blood ammonia concentrations above normal values (35 μmol/L). Recently, a similar study was conducted in elderly men (∼72 y old). A breakpoint in leucine oxidation was observed at 431 mg ⋅ kg^-1 ⋅ d^-1 (95% CI: 351, 511 mg ⋅ kg^-1 ⋅ d^-1), with blood ammonia concentrations above normal (35 μmol/L) at leucine intakes >550 mg ⋅ kg^-1 ⋅ d^-1 Taking the data together, the UL for leucine intake in healthy elderly men could be set at a value similar to young men, at 500 mg ⋅ kg^-1 ⋅ d^-1, or ∼35 g/d for an individual weighing 70 kg; or, as a cautious estimate, the leucine UL could also be considered as 351 mg ⋅ kg^-1 ⋅ d^-1 (the lower 95% CI), which would be ∼24.5 g/d for an elderly individual weighing 70 kg. These studies to determine the UL for leucine in humans are acute diet studies, and future studies with additional biomarkers and long-term supplementation of leucine will be necessary.

Human Protein and Amino Acid Requirements

Human protein and amino acid nutrition encompasses a wide, complex, frequently misunderstood, and often contentious area of clinical research and practice. This tutorial explains the basic biochemical and physiologic principles that underlie our current understanding of protein and amino acid nutrition. The following topics are discussed: (1) the identity, measurement, and essentiality of nutritional proteins; (2) the definition and determination of minimum requirements; (3) nutrition adaptation; (4) obligatory nitrogen excretion and the minimum protein requirement; (5) minimum versus optimum protein intakes; (6) metabolic responses to surfeit and deficient protein intakes; (7) body composition and protein requirements; (8) labile protein; (9) N balance; (10) the principles of protein and amino acid turnover, including an analysis of the controversial indicator amino acid oxidation technique; (11) general guidelines for evaluating protein turnover articles; (12) amino acid turnover versus clearance; (13) the protein content of hydrated amino acid solutions; (14) protein requirements in special situations, including protein-catabolic critical illness; (15) amino acid supplements and additives, including monosodium glutamate and glutamine; and (16) a perspective on the future of protein and amino acid nutrition research. In addition to providing practical information, this tutorial aims to demonstrate the importance of rigorous physiologic reasoning, stimulate intellectual curiosity, and encourage fresh ideas in this dynamic area of human nutrition. In general, references are provided only for topics that are not well covered in modern textbooks.

Sarcopenic obesity and complex interventions with nutrition and exercise in community-dwelling older persons--a narrative review

One of the many threats to independent life is the age-related loss of muscle mass and muscle function commonly referred to as sarcopenia. Another important health risk in old age leading to functional decline is obesity. Obesity prevalence in older persons is increasing, and like sarcopenia, severe obesity has been consistently associated with several negative health outcomes, disabilities, falls, and mobility limitations. Both sarcopenia and obesity pose a health risk for older persons per se, but in combination, they synergistically increase the risk for negative health outcomes and an earlier onset of disability. This combination of sarcopenia and obesity is commonly referred to as sarcopenic obesity. The present narrative review reports the current knowledge on the effects of complex interventions containing nutrition and exercise interventions in community-dwelling older persons with sarcopenic obesity. To date, several complex interventions with different outcomes have been conducted and have shown promise in counteracting either sarcopenia or obesity, but only a few studies have addressed the complex syndrome of sarcopenic obesity. Strong evidence exists on exercise interventions in sarcopenia, especially on strength training, and for obese older persons, strength exercise in combination with a dietary weight loss intervention demonstrated positive effects on muscle function and body fat. The differences in study protocols and target populations make it impossible at the moment to extract data for a meta-analysis or give state-of-the-art recommendations based on reliable evidence. A conclusion that can be drawn from this narrative review is that more exercise programs containing strength and aerobic exercise in combination with dietary interventions including a supervised weight loss program and/or protein supplements should be conducted in order to investigate possible positive effects on sarcopenic obesity.

Calorie restriction and methionine restriction in control of endogenous hydrogen sulfide production by the transsulfuration pathway

H2S is a gas easily identified by its distinctive odor. Although environmental exposure to H2S has been viewed alternately as therapeutic or toxic through the centuries, H2S has recently regained recognition for its numerous beneficial biological effects. Most experiments documenting such benefits, including improved glucose tolerance, increased stress resistance, and even lifespan extension, are based on exposure of experimental organisms to exogenous sources of H2S. However, appreciation is growing for the importance of H2S produced endogenously by the evolutionary conserved transsulfuration pathway (TSP) in health and longevity. Recent data implicate H2S produced by the TSP in pleiotropic benefits of dietary restriction (DR), or reduced nutrient/energy intake without malnutrition. DR, best known as the most reliable way to extend lifespan in a wide range of experimental organisms, includes various regimens aimed at either reducing overall calorie intake (calorie restriction, intermittent/every-other-day fasting) or reducing particular nutrients such as protein or the essential amino acid, methionine (methionine restriction), with overlapping functional benefits on stress resistance, metabolic fitness and lifespan. Here we will review the small but growing body of literature linking the TSP to the functional benefits of DR in part through the production of endogenous H2S, with an emphasis on regulation of the TSP and H2S production by diet and mechanisms of beneficial H2S action.

Milk-soluble formula increases food intake and reduces Il6 expression in elderly rat hypothalami

Malnutrition in the elderly is accompanied by several metabolic dysfunctions, especially alterations in energy homeostasis regulation and a loss of insulin responsiveness. Nutritional recommendations aim to enrich food with high protein and energy supplements, and protein composition and lipid quality have been widely studied. Despite the numerous studies that have examined attempts to overcome malnutrition in the elderly through such nutritional supplementation, it is still necessary to study the effects of a combination of protein, lipids, and vitamin D (VitD). This can be done in animal models of elderly malnutrition. In the present study, we investigated the effects of several diet formulae on insulin responsiveness, inflammation, and the hypothalamic expression of key genes that are involved in energy homeostasis control. To mimic elderly malnutrition in humans, elderly Wistar rats were food restricted (R, -50%) for 12 weeks and then refed for 4 weeks with one of four different isocaloric diets: a control diet; a diet where milk soluble protein (MSP) replaced casein; a blend of milk fat, rapeseed, and DHA (MRD); or a full formula (FF) diet that combined MSP and a blend of MRD (FF). All of the refeeding diets contained VitD. We concluded that: (i) food restriction led to the upregulation of insulin receptor in liver and adipose tissue accompanied by increased Tnfα in the hypothalamus; (ii) in all of the refed groups, refeeding led to similar body weight gain during the refeeding period; and (iii) refeeding with MSP and MRD diets induced higher food intake on the fourth week of refeeding, and this increase was associated with reduced hypothalamic interleukin 6 expression.

Citrulline Supplementation Induces Changes in Body Composition and Limits Age-Related Metabolic Changes in Healthy Male Rats

BACKGROUND

Aging is associated with profound metabolic disturbances, and citrulline may be of use to limit them.

OBJECTIVE

The aim of this work was to evaluate the long-term effect of citrulline supplementation on metabolism in healthy aged rats.

METHODS

Twenty-month-old male rats were randomly assigned to be fed (ad libitum) for 12 wk with either a citrulline-enriched diet (1 g ⋅ kg(-1) ⋅  d(-1)) or a standard diet [rendered isonitrogenous by addition of nonessential amino acids (NEAAs)]. Motor activity and muscle strength were measured, body composition was assessed, and muscle metabolism (protein structure, mitochondrial exploration, and transductional factors) and lipid metabolism (lipoprotein composition and sensitivity to oxidative stress) were explored.

RESULTS

Compared with the NEAA-treated group, citrulline supplementation was associated with lower mortality (0% vs. 20%; P = 0.05), 9% higher lean body mass (P < 0.05), and 13% lower fat mass (P < 0.05). Compared with the NEAA-treated group, citrulline-treated rats had greater muscle mass (+14-48% depending on type of muscle; P < 0.05 for tibialis, gastrocnemius, and plantaris). Susceptibility to oxidation of lipoproteins, as measured by the maximal concentration of 7-ketocholesterol after copper-induced VLDL and LDL oxidation, was lower in citrulline-treated rats than in NEAA-treated rats (187 ± 8 μmol/L vs. 243 ± 7 μmol/L; P = 0.0005).

CONCLUSIONS

Citrulline treatment in male aged rats favorably modulates body composition and protects against lipid oxidation and, thus, emerges as an interesting candidate to help prevent the aging process.

Intake of low-dose leucine-rich essential amino acids stimulates muscle anabolism equivalently to bolus whey protein in older women at rest and after exercise

Dysregulated anabolic responses to nutrition/exercise may contribute to sarcopenia; however, these characteristics are poorly defined in female populations. We determined the effects of two feeding regimes in older women (66 ± 2.5 yr; n = 8/group): bolus whey protein (WP-20 g) or novel low-dose leucine-enriched essential amino acids (EAA) [LEAA; 3 g (40% leucine)]. Using [(13)C6]phenylalanine infusions, we quantified muscle (MPS) and albumin (APS) protein synthesis at baseline and in response to both feeding (FED) and feeding plus exercise (FED-EX; 6 × 8 knee extensions at 75% 1-repetition maximum). We also quantified plasma insulin/AA concentrations, whole leg (LBF)/muscle microvascular blood flow (MBF), and muscle anabolic signaling by phosphoimmunoblotting. Plasma insulinemia and EAA/aemia were markedly greater after WP than LEAA (P < 0.001). Neither LEAA nor WP modified LBF in response to FED or FED-EX, whereas MBF increased to a similar extent in both groups only after FED-EX (P < 0.05). In response to FED, both WP and LEAA equally stimulated MPS 0-2 h (P < 0.05), abating thereafter (0-4 h, P > 0.05). In contrast, after FED-EX, MPS increased at 0-2 h and remained elevated at 0-4 h (P < 0.05) with both WP and LEAA. No anabolic signals quantifiably increased after FED, but p70 S6K1 Thr(389) increased after FED-EX (2 h, P < 0.05). APS increased similarly after WP and LEAA. Older women remain subtly responsive to nutrition ± exercise. Intriguingly though, bolus WP offers no trophic advantage over LEAA.

Protein and healthy aging

Our understanding of the potential benefits and challenges of optimizing dietary protein intake in older adults continues to evolve. An overarching hypothesis generated during Protein Summit 2.0 was that consuming an adequate amount of high-quality protein at each meal, in combination with physical activity, may delay the onset of sarcopenia, slow its progression, reduce the magnitude of its functional consequences, or all of these. The potential benefits of young and middle-aged adults adopting a diet pattern whereby adequate protein is consumed at each meal as a countermeasure to sarcopenia are presented and discussed. For example, meeting a protein threshold (∼25-30 g/meal) represents a promising, yet still largely unexplored dietary strategy to help maintain muscle mass and function. For many older adults, breakfast is a carbohydrate-dominated lower-protein meal and represents an opportunity to improve and more evenly distribute daily protein intake. Although both animal and plant-based proteins can provide the required essential amino acids for health, animal proteins generally have a higher proportion of the amino acid leucine. Leucine plays a key role in stimulating translation initiation and muscle protein anabolism and is the focus of ongoing research. Protein requirements should be assessed in the light of habitual physical activity. An evenly distributed protein diet provides a framework that allows older adults to benefit from the synergistic anabolic effect of protein and physical activity. To fully understand the role of dietary protein intake in healthy aging, greater efforts are needed to coordinate and integrate research design and data acquisition and interpretation from a variety of disciplines.

Effective translation of current dietary guidance: understanding and communicating the concepts of minimal and optimal levels of dietary protein

Dietitians and health care providers have critical roles in the translation of the dietary guidance to practice. The protein content of diets for adults can be based on the Recommended Dietary Allowance (RDA) of 0.80 g/kg per day. Alternatively, the most recent Dietary Reference Intakes (DRIs) for macronutrients reflect expanded guidance for assessing protein needs and consider the relative relation of absolute amounts of protein, carbohydrate, and fat to total energy intake in the context of chronic disease prevention. The Acceptable Macronutrient Distribution Range (AMDR) reflects the interrelation between the macronutrients and affords dietitians and clinicians additional flexibility in diet planning. Accounting for the caloric value of RDAs for carbohydrate and fat, "flexible calories" emerge as an opportunity to create varied eating plans that provide for protein intakes in excess of the RDA but within the AMDR. Protein Summit 2.0 highlighted the growing body of scientific evidence documenting the benefits of higher protein intakes at amounts approximating twice the RDA, which include promotion of healthy body weight and preservation of lean body mass and functional ability with age. The essential amino acid (EAA) density of a food also emerged as a novel concept analogous to "nutrient density," which can enable the practitioner to calculate the caloric cost associated with a specific protein source to attain the daily requirement of EAAs to accomplish various health outcomes because these indispensable nutrients have a significant role in protein utilization and metabolic regulation. Tailoring recommendations unique to an individual's varying goals and needs remains a challenge. However, flexibility within the application of DRIs to include consideration of the AMDR provides a sound framework to guide practitioners in effective translation of current dietary guidance with a specific regard for the documented benefits of higher protein intakes.

Protein supplementation with aging

PURPOSE OF REVIEW

To highlight the recent evicence for optimal protein intake and protein supplementation in older adults. A special focus has been placed on the effects on muscle protein synthesis, strength and overall performance in this population.

RECENT FINDINGS

Although for older adults, some additional evidence on the benefits of a higher protein intake than 0.8 g/kg body weight per day has been provided, the results of studies focusing on the timing of protein intake over the day have been contradictory. Supplementation with so-called 'fast' proteins, which are also rich in leucine, for example whey protein, proved superior with regard to muscle protein synthesis. First studies in frail older persons showed increased strength after supplementation with milk protein, whereas the combination with physical exercise increased muscle mass without additional benefit for strength or functionality.

SUMMARY

Recent evidence suggests positive effects of protein supplementation on muscle protein synthesis, muscle mass and muscle strength. However, as most studies included only small numbers of participants for short treatment periods, larger studies with longer duration are necessary to support the clinical relevance of these observations.

Nutritional influences over the life course on lean body mass of individuals in developing countries

The double burden of childhood undernutrition and adult-onset adiposity in transitioning societies poses a significant public health challenge. The development of suboptimal lean body mass (LBM) could partly explain the link between these two forms of malnutrition. This review examines the evidence on both the role of nutrition in “developmental programming” of LBM and the nutritional influences that affect LBM throughout the life course. Studies from developing countries assessing the relationship of early nutrition with later LBM provide important insights. Overall, the evidence is consistent in suggesting a positive association of early nutritional status (indicated by birth weight and growth during first 2 years) with LBM in later life. Evidence on the impact of maternal nutritional supplementation during pregnancy on later LBM is inconsistent. In addition, the role of nutrients (protein, zinc, calcium, vitamin D) that can affect LBM throughout the life course is described. Promoting optimal intakes of these important nutrients throughout the life course is important for reducing childhood undernutrition as well as for improving the LBM of adults.

The effectiveness of leucine on muscle protein synthesis, lean body mass and leg lean mass accretion in older people: a systematic review and meta-analysis

In the present study, we performed a meta-analysis to assess the ability of leucine supplementation to increase the muscle protein fraction synthetic rate and to augment lean body mass or leg lean mass in elderly patients. A literature search was conducted on Medline, Cochrane, EMBASE and Google Scholar databases up to 31 December 2013 for clinical trials that investigated the administration of leucine as a nutrient that affects muscle protein metabolism and muscle mass in elderly subjects. The included studies were randomised controlled trials. The primary outcome for the meta-analysis was the protein fractional synthetic rate. Secondary outcomes included lean body mass and leg lean mass. A total of nine studies were included in the meta-analysis. The results showed that the muscle protein fractional synthetic rate after intervention significantly increased in the leucine group compared with the control group (pooled standardised difference in mean changes 1·08, 95% CI 0·50, 1·67; P< 0·001). No difference was found between the groups in relation to lean body mass (pooled standardised difference in mean changes 0·18, 95% CI - 0·18, 0·54; P= 0·318) or leg lean mass (pooled standardised difference in mean changes 0·006, 95% CI - 0·32, 0·44; P= 0·756). These findings suggest that leucine supplementation is useful to address the age-related decline in muscle mass in elderly individuals, as it increases the muscle protein fractional synthetic rate.

Inclusion of red meat in healthful dietary patterns

Dietary patterns are an important concept in dietary recommendations. The Western pattern is most commonly defined as a diet characterized by high intakes of refined grains, sugar and red meat, and has been shown to be associated with increased risks for certain types of cancer, coronary heart disease, diabetes, and obesity. However, isolating the independent effects of individual foods on health outcomes is central to helping individuals choose foods to build healthier dietary patterns to which they can adhere. Red meat is a popular source of high quality protein and provides a variety of essential nutrients that improve overall diet quality. It is also a source of saturated fatty acids, which observational evidence suggests are associated with heart disease, although recent data challenge this. Several studies have shown that lean red meat can be successfully included in recommended heart-healthy dietary patterns without detriment to blood lipids. Furthermore, increased dietary protein has been shown to promote healthy body weight and composition, in part by increasing satiety, and to improve vitality and stamina.

High protein intake is associated with low prevalence of frailty among old Japanese women: a multicenter cross-sectional study

Background

Protein intake has been inversely associated with frailty. However, no study has examined the effect of the difference of protein sources (animal or plant) or the amino acid composing the protein on frailty. Therefore, we examined the association of protein and amino acid intakes with frailty among elderly Japanese women.

Methods

A total of 2108 grandmothers or acquaintances of dietetic students aged 65 years and older participated in this cross-sectional multicenter study, which was conducted in 85 dietetic schools in 35 prefectures of Japan. Intakes of total, animal, and plant protein and eight selected amino acids were estimated from a validated brief-type self-administered diet history questionnaire and amino acid composition database. Frailty was defined as the presence of three or more of the following four components: slowness and weakness (two points), exhaustion, low physical activity, and unintentional weight loss.

Results

The number of subjects with frailty was 481 (23%). Adjusted ORs (95% CI) for frailty in the first, second, third, fourth, and fifth quintiles of total protein intake were 1.00 (reference), 1.02 (0.72, 1.45), 0.64 (0.45, 0.93), 0.62 (0.43, 0.90), and 0.66 (0.46, 0.96), respectively (P for trend = 0.001). Subjects categorized to the third, fourth, and fifth quintiles of total protein intake (>69.8 g/d) showed significantly lower ORs than those to the first quintile (all P <0.03). The intakes of animal and plant protein and all selected amino acids were also inversely associated with frailty (P for trend <0.04), with the multivariate adjusted OR in the highest compared to the lowest quintile of 0.73 for animal protein and 0.66 for plant protein, and 0.67-0.74 for amino acids, albeit that the ORs for these dietary variables were less marked than those for total protein.

Conclusions

Total protein intake was significantly inversely associated with frailty in elderly Japanese women. The association of total protein with frailty may be observed regardless of the source of protein and the amino acid composing the protein.

Nutritional influences on age-related skeletal muscle loss

Age-related muscle loss impacts on whole-body metabolism and leads to frailty and sarcopenia, which are risk factors for fractures and mortality. Although nutrients are integral to muscle metabolism the relationship between nutrition and muscle loss has only been extensively investigated for protein and amino acids. The objective of the present paper is to describe other aspects of nutrition and their association with skeletal muscle mass. Mechanisms for muscle loss relate to imbalance in protein turnover with a number of anabolic pathways of which the mechanistic TOR pathway and the IGF-1–Akt–FoxO pathways are the most characterised. In terms of catabolism the ubiquitin proteasome system, apoptosis, autophagy, inflammation, oxidation and insulin resistance are among the major mechanisms proposed. The limited research associating vitamin D, alcohol, dietary acid–base load, dietary fat and anti-oxidant nutrients with age-related muscle loss is described. Vitamin D may be protective for muscle loss; a more alkalinogenic diet and diets higher in the anti-oxidant nutrients vitamin C and vitamin E may also prevent muscle loss. Although present recommendations for prevention of sarcopenia focus on protein, and to some extent on vitamin D, other aspects of the diet including fruits and vegetables should be considered. Clearly, more research into other aspects of nutrition and their role in prevention of muscle loss is required.