Food-First Approach to Enhance the Regulation of Post-exercise Skeletal Muscle Protein Synthesis and Remodeling

Reconsidering the pre-eminence of dietary leucine and plasma leucinemia for predicting the stimulation of postprandial muscle protein synthesis rates

The regulation of postprandial muscle protein synthesis (MPS) with or without physical activity has been an intensely studied area within nutrition and physiology. The leucine content of dietary protein and the subsequent plasma leucinemia it elicits postingestion is often considered the primary drivers of the postprandial MPS response. This concept, generally known as the leucine "trigger" hypothesis, has also been adopted within more applied aspects of nutrition. Our view is that recent evidence is driving a more nuanced picture of the regulation of postprandial MPS by revealing a compelling dissociation between ingested leucine or plasma leucinemia and the magnitude of the postprandial MPS response. Much of this lack of coherence has arisen as experimental progress has demanded relevant studies move beyond reliance on isolated amino acids and proteins to use increasingly complex protein-rich meals, whole foods, and mixed meals. Our overreliance on the centrality of leucine in this field has been reflected in 2 recent systematic reviews. In this perspective, we propose a re-evaluation of the pre-eminent role of these leucine variables in the stimulation of postprandial MPS. We view the development of a more complex intellectual framework now a priority if we are to see continued progress concerning the mechanistic regulation of postprandial muscle protein turnover, but also consequential from an applied perspective when evaluating the value of novel dietary protein sources.

Protein Requirements for Maximal Muscle Mass and Athletic Performance Are Achieved with Completely Plant-Based Diets Scaled to Meet Energy Needs: A Modeling Study in Professional American Football Players

American football players consume large quantities of animal-sourced protein in adherence with traditional recommendations to maximize muscle development and athletic performance. This contrasts with dietary guidelines, which recommend reducing meat intake and increasing consumption of plant-based foods to promote health and reduce the risk of chronic disease. The capacity of completely plant-based diets to meet the nutritional needs of American football players has not been studied. This modeling study scaled dietary data from a large cohort following completely plant-based diets to meet the energy requirements of professional American football players to determine whether protein, leucine, and micronutrient needs for physical performance and health were met. The Cunningham equation was used to estimate calorie requirements. Nutrient intakes from the Adventist Health Study 2 were then scaled to this calorie level. Protein values ranged from 1.6-2.2 g/kg/day and leucine values ranged from 3.8-4.1 g/meal at each of four daily meals, therefore meeting and exceeding levels theorized to maximize muscle mass, muscle strength, and muscle protein synthesis, respectively. Plant-based diets scaled to meet the energy needs of professional American football players satisfied protein, leucine, and micronutrient requirements for muscle development and athletic performance. These findings suggest that completely plant-based diets could bridge the gap between dietary recommendations for chronic disease prevention and athletic performance in American football players.

Ingestion of a variety of non-animal-derived dietary protein sources results in diverse postprandial plasma amino acid responses which differ between young and older adults

Whole-body tissue protein turnover is regulated, in part, by the postprandial rise in plasma amino acid concentrations, although minimal data exist on the amino acid response following non-animal-derived protein consumption. We hypothesised that the ingestion of novel plant- and algae-derived dietary protein sources would elicit divergent plasma amino acid responses when compared with vegan- and animal-derived control proteins. Twelve healthy young (male (m)/female (f): 6/6; age: 22 ± 1 years) and 10 healthy older (m/f: 5/5; age: 69 ± 2 years) adults participated in a randomised, double-blind, cross-over trial. During each visit, volunteers consumed 30 g of protein from milk, mycoprotein, pea, lupin, spirulina or chlorella. Repeated arterialised venous blood samples were collected at baseline and over a 5-h postprandial period to assess circulating amino acid, glucose and insulin concentrations. Protein ingestion increased plasma total and essential amino acid concentrations (P < 0·001), to differing degrees between sources (P < 0·001), and the increase was further modulated by age (P < 0·001). Postprandial maximal plasma total and essential amino acid concentrations were highest for pea (2828 ± 106 and 1480 ± 51 µmol·l-1) and spirulina (2809 ± 99 and 1455 ± 49 µmol·l-1) and lowest for chlorella (2053 ± 83 and 983 ± 35 µmol·l-1) (P < 0·001), but were not affected by age (P > 0·05). Postprandial total and essential amino acid availabilities were highest for pea, spirulina and mycoprotein and lowest for chlorella (all P < 0·05), but no effect of age was observed (P > 0·05). The ingestion of a variety of novel non-animal-derived dietary protein sources elicits divergent plasma amino acid responses, which are further modulated by age.

Acute Microbial Protease Supplementation Increases Net Postprandial Plasma Amino Acid Concentrations After Pea Protein Ingestion in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Digestibility is a primary factor in determining the quality of dietary protein. Microbial protease supplementation may be a strategy for improving protein digestion and subsequent postprandial plasma amino acid availability.

OBJECTIVES

To assess the effect of co-ingesting a microbial protease mixture with pea protein on postprandial plasma amino acid concentrations.

DESIGN

A mixture of 3 microbial protease preparations (P3) was tested for proteolytic efficacy in an in vitro static simulation of gastrointestinal digestion. Subsequently, in a randomized, double-blind, placebo-controlled crossover trial, 24 healthy adults (27 ± 4 y; 12 females, 12 males) ingested 25 g pea protein isolate (20 g protein, 2.2 g fat) with either P3 or maltodextrin placebo (PLA). Blood samples were collected at baseline and throughout a 0‒5 h postprandial period and both the early (0-2 h) iAUC and total (0-5 h) iAUC were examined.

RESULTS

Plasma glucose concentrations decreased in both conditions (P < 0.001), with higher concentrations after P3 ingestion compared with PLA (P < 0.001). Plasma insulin concentrations increased for both conditions (P < 0.001) with no difference between conditions (P = 0.331). Plasma total amino acid (TAA) concentrations increased over time (P < 0.001) with higher concentrations observed for P3 compared with PLA (P = 0.010) during the 0‒5 h period. There was a trend for elevated essential amino acid (EAA) concentrations for P3 compared with PLA (P = 0.099) during the 0‒5 h postprandial period but not for leucine (P = 0.282) or branched-chain amino acids (BCAA, P = 0.410). The early net exposure (0‒2 h iAUC) to amino acids (leucine, BCAA, EAA, and TAA) was higher for P3 compared with PLA (all, P < 0.05).

CONCLUSIONS

Microbial protease co-ingestion increases plasma TAA concentrations (0-5 h) and leucine, BCAA, EAA, and TAA availability in the early postprandial period (0‒2 h) compared with ingesting pea protein with placebo in healthy adults.

Completely Plant-Based Diets That Meet Energy Requirements for Resistance Training Can Supply Enough Protein and Leucine to Maximize Hypertrophy and Strength in Male Bodybuilders: A Modeling Study

Despite increasing awareness of plant-based diets for health and athletic performance, athletes are cautioned that careful dietary monitoring is necessary. Whether commonly consumed plant-based diets are nutritionally adequate for maximal muscular hypertrophy remains unknown. This modeling study assessed the nutrient composition of completely plant-based diets scaled to the caloric demands of maximal muscle mass and strength development in adult male bodybuilders. To model calorie requirements, anthropometric data from bodybuilders were input into the Tinsley resting metabolic rate prediction equation, and an appropriate physical activity factor and calorie surplus were applied. Dietary data from a large cohort following completely plant-based diets were then scaled to meet these needs. Modeled intakes for nutrients of interest were calculated as 1.8 g/kg/day of protein and 2.75 g/meal of leucine, which surpass mean requirements for maximal increases in muscle mass and strength and muscle protein synthesis, respectively. Daily levels for all micronutrients, except vitamin D, also exceeded requirements. Saturated fat levels were aligned with dietary guidelines, although sodium levels exceeded recommended limits. Consumption of larger portions of commonplace plant-based diets, scaled to meet the energy demands of maximal accrual of muscle mass and strength, satisfied protein and leucine requirements without the need for additional planning.

Effects of Whey Protein Combined with Amylopectin/Chromium on the Muscle Protein Synthesis and mTOR Phosphorylation in Exercised Rats

This study aimed to examine the impact of varying doses of whey protein (WP) and amylopectin/chromium complex (ACr) supplementation on muscle protein synthesis (MPS), amino acid and insulin levels, and the rapamycin (mTOR) signaling pathways in exercised rats. A total of 72 rats were randomly divided into nine groups: (1) Exercise (Ex), (2) Ex + WPI to (5) Ex + WPIV with various oral doses of whey protein (0.465, 1.55, 2.33, and 3.1 g/kg) and (6) Ex + WPI + ACr to (9) Ex + WPIV + ACr with various doses of whey protein combined with 0.155 g/kg ACr. On the day of single-dose administration, the products were given by oral gavage after exercise. To measure the protein fractional synthesis rate (FSR), a bolus dose of deuterium-labeled phenylalanine was given, and its effects were evaluated 1 h after supplementation. Rats that received 3.1 g/kg of whey protein (WP) combined with ACr exhibited the most significant increase in muscle protein synthesis (MPS) compared to the Ex group (115.7%, p < 0.0001). In comparison to rats that received the same dose of WP alone, those given the combination of WP and ACr at the same dosage showed a 14.3% increase in MPS (p < 0.0001). Furthermore, the WP (3.1 g/kg) + ACr group exhibited the highest elevation in serum insulin levels when compared to the Ex group (111.9%, p < 0.0001). Among the different groups, the WP (2.33 g/kg) + ACr group demonstrated the greatest increase in mTOR levels (224.2%, p < 0.0001). Additionally, the combination of WP (2.33 g/kg) and ACr resulted in a 169.8% increase in 4E-BP1 levels (p < 0.0001), while S6K1 levels rose by 141.2% in the WP (2.33 g/kg) + ACr group (p < 0.0001). Overall, supplementation with various doses of WP combined with ACr increased MPS and enhanced the mTOR signaling pathway compared to WP alone and the Ex group.

Acid-active proteases to optimize dietary protein digestibility: a step towards sustainable nutrition

Introduction

Historically, prioritizing abundant food production often resulted in overlooking nutrient quality and bioavailability, however, environmental concerns have now propelled sustainable nutrition and health efficacy to the forefront of global attention. In fact, increasing demand for protein is the major challenge facing the food system in the 21st century with an estimation that 70% more food is needed by 2050. This shift has spurred interest in plant-based proteins for their sustainability and health benefits, but most alternative sources of protein are poorly digestible. There are two approaches to solve digestibility: improve the digestibility of food proteins or improve the digestive capacity of consumers. Enhancing nutrient digestibility and bioavailability across diverse protein sources is crucial, with proteases presenting a promising avenue. Research, inspired by the proteases of human breast milk, has demonstrated that exogenous microbial proteases can activate within the human digestive tract and substantially increase the digestion of targeted proteins that are otherwise difficult to fully digest.

Methods

Here, we introduce the use of an acid-active family of bacterial proteases (S53) to improve the digestibility and nutritional quality of a variety of protein sources, evaluated using the INFOGEST 2.0 protocol.

Results

Results from in vitro digestibility indicate that the most effective protease in the S53 family substantially improves the digestibility of an array of animal and plant-derived proteins-soy, pea, chickpea, rice, casein, and whey. On average, this protease elevated protein digestibility by 115% during the gastric phase and by 15% in the intestinal phase, based on the degree of hydrolysis.

Discussion

The widespread adoption of these proteases has the potential to enhance nutritional value and contribute to food security and sustainability. This approach would complement ongoing efforts to improve proteins in the food supply, increase the quality of more sustainable protein sources and aid in the nourishment of patients with clinically compromised, fragile intestines and individuals like older adults and high-performance athletes who have elevated protein needs.

Management of disease-related malnutrition: a real-world experience with a novel concentrated high-protein energy-dense oral nutritional supplement

OBJECTIVE

Despite the availability of a wide range of oral nutritional supplements (ONS) offerings, individuals with malnutrition are still struggling to meet their nutritional targets. A new concentrated and high-protein energy-dense ONS (≥2.1 kcal/mL;32 g protein/200 mL) with high-quality protein (60% whey protein) has emerged as a pivotal formula to reach the patient's energy-protein requirements, enhance compliance, and maximize stimulation of muscle protein synthesis, key factors driving better nutritional, functional, and clinical outcomes. The purpose of this article is to provide our clinical experience using this new nutritionally concentrated ONS as a therapeutic strategy for patients with DRM.

METHODS

Three clinical cases have been examined using new assessment procedures and a new form of nutritional therapy, and their impact on the nutritional and functional outcomes in patients with moderate-to-severe DRM.

RESULTS

A tailored individualized nutritional interventions improved anthropometric, biochemical, and functional outcomes (Case 1,2, and 3) assessed using hand grip strength, bioimpedance and muscle ultrasound, and as well as good gastrointestinal tolerance (Case 1) and compliance to the ONS in patients with DRM (Case 1,2,3).

CONCLUSION

The use of this novel high-protein energy-dense formula with high-quality protein source (≥2.1 kcal/mL; 32 g protein/200 mL; 60% whey protein) overcome common practical challenges in the medical nutrition therapy of patients with DRM, either because these patients require a highly concentrated formulation to meet nutritional requirements due to loss of appetite, lack of interest in food, and high caloric-protein needs due to disease, and a large quantity and quality of protein to optimize muscle recovery due to sarcopenia, common in patients with moderate-severe malnutrition.

Dietary proteins modulate high-density lipoprotein characteristics in a sex-specific way in Apoe-deficient mice

OBJECTIVES

The type and amount of dietary protein have become a topic of renewed interest, considering their involvement in several diseases. However, little attention has been devoted to the effect of avian proteins despite their wide human consumption. In a previous study, we saw that compared with soybean protein, the consumption of avian proteins, depending on sex, resulted in similar or lower atherosclerosis with a higher paraoxonase 1 activity, an antioxidant enzyme carried by high-density lipoproteins (HDL). This suggests that under these conditions, the HDL lipoproteins may undergo important changes. The aim of this research was to study the influence of soybean, chicken, and turkey proteins on the characteristics of HDL.

METHODS

Male and female Apoe-deficient mice were fed purified Western diets based on the AIN-93 diet, differing only in the protein source, for 12 wk. After this period, blood and liver samples were taken for analysis of HDL composition and hepatic expression of genes related to HDL metabolism (Abca1, Lcat, Pltp, Pon1, and Scarb1). Depending on sex, these genes define a different network of interactions. Females consuming the turkey protein-containing diet showed decreased atherosclerotic foci, which can be due to larger very-low-density lipoproteins (VLDLs) calculated by molar ratio triacylglycerols/VLDL cholesterol and higher expression of Lcat. In contrast, in males, a higher ratio of paraoxonase1 to apolipoprotein A1 decreased the oxidative status of the different lipoproteins, and augmented Abca1 expression was observed.

CONCLUSIONS

The source of protein has an effect on the development of atherosclerosis depending on sex by modifying HDL characteristics and the expression of genes involved in their properties.

Algae Ingestion Increases Resting and Exercised Myofibrillar Protein Synthesis Rates to a Similar Extent as Mycoprotein in Young Adults

BACKGROUND

Spirulina [SPIR] (cyanobacterium) and chlorella [CHLO] (microalgae) are foods rich in protein and essential amino acids; however, their capacity to stimulate myofibrillar protein synthesis (MyoPS) in humans remains unknown.

OBJECTIVES

We assessed the impact of ingesting SPIR and CHLO compared with an established high-quality nonanimal-derived dietary protein source (fungal-derived mycoprotein [MYCO]) on plasma amino acid concentrations, as well as resting and postexercise MyoPS rates in young adults.

METHODS

Thirty-six healthy young adults (age: 22 ± 3 y; BMI: 23 ± 3 kg·m-2; male [m]/female [f], 18/18) participated in a randomized, double-blind, parallel-group trial. Participants received a primed, continuous infusion of L-[ring-2H5]-phenylalanine and completed a bout of unilateral-resistance leg exercise before ingesting a drink containing 25 g protein from MYCO (n = 12; m/f, 6/6), SPIR (n = 12; m/f, 6/6), or CHLO (n = 12; m/f, 6/6). Blood and bilateral muscle samples were collected at baseline and during a 4-h postprandial and postexercise period to assess the plasma amino acid concentrations and MyoPS rates in rested and exercised tissue.

RESULTS

Protein ingestion increased the plasma total and essential amino acid concentrations (time effects; all P < 0.001), but most rapidly and with higher peak responses following the ingestion of SPIR compared with MYCO and CHLO (P < 0.05), and MYCO compared with CHLO (P < 0.05). Protein ingestion increased MyoPS rates (time effect; P < 0.001) in both rested (MYCO, from 0.041 ± 0.032 to 0.060 ± 0.015%·h-1; SPIR, from 0.042 ± 0.030 to 0.066 ± 0.022%·h-1; and CHLO, from 0.037 ± 0.007 to 0.055 ± 0.019%·h-1, respectively) and exercised tissue (MYCO, from 0.046 ± 0.014 to 0.092 ± 0.024%·h-1; SPIR, from 0.038 ± 0.011 to 0.086 ± 0.028%·h-1; and CHLO, from 0.048 ± 0.019 to 0.090 ± 0.024%·h-1, respectively), with no differences between groups (interaction effect; P > 0.05), but with higher rates in exercised compared with rested muscle (time × exercise effect; P < 0.001).

CONCLUSIONS

The ingestion of a single bolus of algae-derived SPIR and CHLO increases resting and postexercise MyoPS rates to a comparable extent as MYCO, despite divergent postprandial plasma amino acid responses.

Nutrient synergy: definition, evidence, and future directions

Nutrient synergy refers to the concept that the combined effects of two or more nutrients working together have a greater physiological impact on the body than when each nutrient is consumed individually. While nutrition science traditionally focuses on isolating single nutrients to study their effects, it is recognized that nutrients interact in complex ways, and their combined consumption can lead to additive effects. Additionally, the Dietary Reference Intakes (DRIs) provide guidelines to prevent nutrient deficiencies and excessive intake but are not designed to assess the potential synergistic effects of consuming nutrients together. Even the term synergy is often applied in different manners depending on the scientific discipline. Considering these issues, the aim of this narrative review is to investigate the potential health benefits of consuming different nutrients and nutrient supplements in combination, a concept we define as nutrient synergy, which has gained considerable attention for its impact on overall well-being. We will examine how nutrient synergy affects major bodily systems, influencing systemic health. Additionally, we will address the challenges associated with promoting and conducting research on this topic, while proposing potential solutions to enhance the quality and quantity of scientific literature on nutrient synergy.

Dietary protein recommendations to support healthy muscle ageing in the 21st century and beyond: considerations and future directions

This review explores the evolution of dietary protein intake requirements and recommendations, with a focus on skeletal muscle remodelling to support healthy ageing based on presentations at the 2023 Nutrition Society summer conference. In this review, we describe the role of dietary protein for metabolic health and ageing muscle, explain the origins of protein and amino acid (AA) requirements and discuss current recommendations for dietary protein intake, which currently sits at about 0⋅8 g/kg/d. We also critique existing (e.g. nitrogen balance) and contemporary (e.g. indicator AA oxidation) methods to determine protein/AA intake requirements and suggest that existing methods may underestimate requirements, with more contemporary assessments indicating protein recommendations may need to be increased to >1⋅0 g/kg/d. One example of evolution in dietary protein guidance is the transition from protein requirements to recommendations. Hence, we discuss the refinement of protein/AA requirements for skeletal muscle maintenance with advanced age beyond simply the dose (e.g. source, type, quality, timing, pattern, nutrient co-ingestion) and explore the efficacy and sustainability of alternative protein sources beyond animal-based proteins to facilitate skeletal muscle remodelling in older age. We conclude that, whilst a growing body of research has demonstrated that animal-free protein sources can effectively stimulate and support muscle remodelling in a manner that is comparable to animal-based proteins, food systems need to sustainably provide a diversity of both plant and animal source foods, not least for their protein content but other vital nutrients. Finally, we propose some priority research directions for the field of protein nutrition and healthy ageing.

A focus on leucine in the nutritional regulation of human skeletal muscle metabolism in ageing, exercise and unloading states

Muscle protein synthesis (MPS) and muscle protein breakdown (MPB) are influenced through dietary protein intake and physical (in)activity, which it follows, regulate skeletal muscle (SKM) mass across the lifespan. Following consumption of dietary protein, the bio-availability of essential amino acids (EAA), and primarily leucine (LEU), drive a transient increase in MPS with an ensuing refractory period before the next MPS stimulation is possible (due to the "muscle full" state). At the same time, MPB is periodically constrained via reflex insulin actions. Layering exercise on top of protein intake increases the sensitivity of SKM to EAA, therefore extending the muscle full set-point (∼48 h), to permit long-term remodelling (e.g., hypertrophy). In contrast, ageing and physical inactivity are associated with a premature muscle full set-point in response to dietary protein/EAA and contractile activity. Of all the EAA, LEU is the most potent stimulator of the mechanistic target of rapamycin complex 1 (mTORC1)-signalling pathway, with the phosphorylation of mTORC1 substrates increasing ∼3-fold more than with all other EAA. Furthermore, maximal MPS stimulation is also achieved following low doses of LEU-enriched protein/EAA, negating the need for larger protein doses. As a result, LEU supplementation has been of long term interest to maximise muscle anabolism and subsequent net protein accretion, especially when in tandem with resistance exercise. This review highlights current knowledge vis-à-vis the anabolic effects of LEU supplementation in isolation, and in enriched protein/EAA sources (i.e., EAA and/or protein sources with added LEU), in the context of ageing, exercise and unloading states.

Evaluation of pea/rice and amylopectin/chromium as an alternative protein source to improve muscle protein synthesis in rats

BACKGROUND

A preclinical study reported that the combination of an amylopectin/chromium complex (ACr) of branched-chain amino acids (BCAA) significantly enhanced muscle protein synthesis (MPS). This study was conducted to determine the effects of the addition of ACr complex to a pea/rice (PR) protein on MPS, insulin, muslin levels, and the mTOR pathway in exercised rats.

METHODS

Twenty-four rats were divided into three groups: (i) exercise (Ex); (ii) Ex + PR 1:1 blend (0.465 g/kg BW); (iii) Ex + PR + ACr (0.155 g/kg BW). On the day of single-dose administration, after the animals were exercised at 26/m/min for 2 h, the supplement was given by oral gavage. The rats were injected with a bolus dose (250 mg/kg BW, 25 g/L) of deuterium-labeled phenylalanine to determine the protein fractional synthesis rate (FSR) one h after consuming the study product.

RESULTS

The combination of PR and ACr enhanced MPS by 42.55% compared to the Ex group, while Ex + PR alone increased MPS by 30.2% over the Ex group (p < 0.0001) in exercised rats. Ex + PR plus ACr significantly enhanced phosphorylation of mTOR and S6K1 (p < 0.0001), and 4E-BP1 (p < 0.001) compared to the Ex (p < 0.0001). PR to ACr also significantly increased insulin and musclin levels (p < 0.0001) in exercised rats. Additionally, compared to Ex + PR alone, Ex + PR + ACr enhanced mTOR (p < 0.0001) and S6K1 (p < 0.0001) levels.

CONCLUSION

These data suggested that PR + ACr may provide an alternative to animal proteins for remodeling and repairing muscle by stimulating MPS and mTOR signaling pathways in post-exercised rats. More preclinical and clinical human studies on combining pea/rice and amylopectin/chromium complex are required.

Underpinning the Food Matrix Regulation of Postexercise Myofibrillar Protein Synthesis by Comparing Salmon Ingestion With the Sum of Its Isolated Nutrients in Healthy Young Adults

BACKGROUND

Protein is most commonly consumed as whole foods as opposed to single nutrients. However, the food matrix regulation of the postprandial muscle protein synthetic response has received little attention.

OBJECTIVES

The purpose of this study was to assess the effects of eating salmon (SAL) and of ingesting the same nutrients as an isolated mixture of crystalline amino acids and fish oil (ISO) on the stimulation of postexercise myofibrillar protein synthesis (MPS) and whole-body leucine oxidation rates in healthy young adults.

METHODS

Ten recreationally active adults (24 ± 4 y; 5 men, 5 women) performed an acute bout of resistance exercise, followed by the ingestion of SAL or ISO in a crossover fashion. Blood, breath, and muscle biopsies were collected at rest and after exercise during primed continuous infusions of L-[ring-2H5]phenylalanine and L-[1-13C]leucine. All data are presented as means ± SD and/or mean differences (95% CIs).

RESULTS

Postprandial essential amino acid (EAA) concentrations peaked earlier (P = 0.024) in the ISO group than those in the SAL group. Postprandial leucine oxidation rates increased over time (P < 0.001) and peaked earlier in the ISO group (1.239 ± 0.321 nmol/kg/min; 63 ± 25 min) than those in the SAL group (1.230 ± 0.561 nmol/kg/min; 105 ± 20 min; P = 0.003). MPS rates for SAL (0.056 ± 0.022 %/h; P = 0.001) and ISO (0.046 ± 0.025 %/h; P = 0.025) were greater than the basal rates (0.020 ± 0.011 %/h) during the 0- to 5-h recovery period, with no differences between conditions (P = 0.308).

CONCLUSION

We showed that the postexercise ingestion of SAL or ISO stimulate postexercise MPS rates with no differences between the conditions. Thus, our results indicate that ingesting protein from SAL as a whole-food matrix is similarly anabolic to ISO in healthy young adults. This trial was registered at www.

CLINICALTRIALS

gov as NCT03870165.

Influence of protein source (cricket, pea, whey) on amino acid bioavailability and activation of the mTORC1 signaling pathway after resistance exercise in healthy young males

PURPOSE

New dietary proteins are currently introduced to replace traditional animal protein sources. However, not much is known about their bioaccessibility and ability to stimulate muscle protein synthesis compared to the traditional protein sources. We aimed to compare effects of ingesting a protein bolus (0.25 g/kg fat free mass) of either cricket (insect), pea, or whey protein on circulating amino acid levels and activation of the mTORC1 signaling pathway in the skeletal muscle at rest and after exercise.

METHODS

In a randomized parallel controlled trial, young males (n = 50) performed a one-legged resistance exercise followed by ingestion of one of the three protein sources. Blood samples were collected before and in the following 4 h after exercise. Muscle biopsies were obtained at baseline and after 3 h from the non-exercised and exercised leg.

RESULTS

Analysis of blood serum showed a significantly higher concentration of amino acids after ingestion of whey protein compared to cricket and pea protein. No difference between protein sources in activation of the mTORC1 signaling pathway was observed either at rest or after exercise.

CONCLUSION

Amino acid blood concentration after protein ingestion was higher for whey than pea and cricket protein, whereas activation of mTORC1 signaling pathway at rest and after exercise did not differ between protein sources.

TRIAL REGISTRATION NUMBER

Clinicaltrials.org ID NCT04633694.

Carbohydrates and Endurance Exercise: A Narrative Review of a Food First Approach

Carbohydrate (CHO) supplements such as bars, gels, drinks and powders have become ubiquitous as effective evidence-based CHO sources that improve endurance exercise performance. However, athletes are increasingly turning to more cost-effective ‘food-first’ approaches for CHO ingestion to improve exercise performance. Mixed CHO foods including cooked lentils, oats, honey, raisins, rice, and potatoes are all effective pre-exercise CHO food sources. Caution is advised when selecting some of these foods as a primary CHO source, as some athletes may be prone to gastrointestinal discomfort—especially regarding those foods where the quantities required for recommended CHO intake may be voluminous (e.g., potatoes). Palatability may be another barrier to the ingestion of some of these CHO-rich foods. Although most of these CHO-rich foods appear effective for exercise performance or recovery when consumed pre- and post-exercise, not all are viable to ingest during exercise due to difficulties in the quantities required, transport, and/or gastrointestinal discomfort. Raisins, bananas and honey may be particularly useful CHO foods for consumption during exercise, as they are easily transportable. Athletes should trial CHO food sources before, during and/or following training before implementation during competition.

Alternative dietary protein sources to support healthy and active skeletal muscle aging

To mitigate the age-related decline in skeletal muscle quantity and quality, and the associated negative health outcomes, it has been proposed that dietary protein recommendations for older adults should be increased alongside an active lifestyle and/or structured exercise training. Concomitantly, there are growing environmental concerns associated with the production of animal-based dietary protein sources. The question therefore arises as to where this dietary protein required for meeting the protein demands of the rapidly aging global population should (or could) be obtained. Various non-animal-derived protein sources possess favorable sustainability credentials, though much less is known (compared with animal-derived proteins) about their ability to influence muscle anabolism. It is also likely that the anabolic potential of various alternative protein sources varies markedly, with the majority of options remaining to be investigated. The purpose of this review was to thoroughly assess the current evidence base for the utility of alternative protein sources (plants, fungi, insects, algae, and lab-grown "meat") to support muscle anabolism in (active) older adults. The solid existing data portfolio requires considerable expansion to encompass the strategic evaluation of the various types of dietary protein sources. Such data will ultimately be necessary to support desirable alterations and refinements in nutritional guidelines to support healthy and active aging, while concomitantly securing a sustainable food future.

Nutritional profiling and contaminant levels of five underutilized fish species in Norway

Exploring and making use of underutilized marine resources can be a sustainable approach to achieve future demands of fish consumption by the ever-growing population. Five species, namely European plaice (Pleuronectes platessa), European flounder (Platichthys flesus), lemon sole (Microstomus kitt), megrim (Lepidorhombus whiffiagonis), and thornback ray (Raja clavate), often captured as by-catch in Norway, were characterized for their nutritional value and potential accumulation of hazardous components. The proximate composition, protein profile, fatty acid profile as well as essential and toxic trace elements and polychlorinated biphenyls (PCBs) were analyzed. Digestible indispensable amino acid (DIAA) ratios and scores (DIAAS) and contributions of omega-3 fatty acids to the diet were calculated. Analysis on proximate composition revealed low fat contents of 0.74 to 1.25% and sufficient protein contents between 16.9 and 24% in the five species. Results of DIAA indicate a profitable distribution, with contributions exceeding the daily intake recommendations for an adult person related to a 200 g fillet. Moreover, findings on the distribution of eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) showed remarkable results, considering that the investigated species are lean fish. All five investigated fish exceed the recommended average daily intake level (AI) of EPA + DHA in a 200 g portion. As to toxic trace elements and PCBs, no significantly elevated levels were found considering a portion size of 200 g. Consequently, the nutritional quality of the investigated fish can be regarded as profitable with overall low potential health risks.

Comparison of nutritional composition between plant-based drinks and cow's milk

The high decline in liquid milk consumption in Western countries has been compensated by the increased consumption of processed dairy products and the rapidly increasing number of new plant-based beverages constantly introduced in the market, advertised as milk substitutes and placed on shelves near milk products. To provide better understanding about the nutritional value of these drinks compared with cow's milk, 27 plant-based drinks of 8 different species and two milk samples were purchased from two big retailers in Switzerland, and their composition regarding protein, carbohydrate, fat, vitamin, and mineral contents and residue load [glyphosate, aminomethylphosphonic acid (AMPA), and arsenic] was analyzed quantitatively and qualitatively. Energy and nutrient intakes were calculated and compared with the dietary reference values for Germany, Austria and Switzerland (D-A-CH). In addition, the digestible indispensable amino acid score (DIAAS) was calculated to estimate the quality of the proteins. Milk contained more energy; fat; carbohydrate; vitamins C, B₂, B₁₂, and A; biotin; pantothenic acid; calcium; phosphorus; and iodine than most plant-based drinks. Soy drinks provided slightly more protein and markedly more vitamins B₁ and B₆, folic acid, and vitamins E and D₂ (with supplemented vitamin D₂) and K₁, magnesium, manganese, iron, and copper than milk and the other plant-based drinks. However, with the exception of cow's milk and soy drinks, which had > 3% protein, most milk alternatives contained ≤ 1% protein; therefore, they cannot be considered good protein sources. In regard to protein quality, milk was outstanding compared with all plant-based drinks and exhibited higher calculated DIAASs. Our results show that the analyzed plant-based drinks are not real alternatives to milk in terms of nutrient composition, even if the actual fortification is taken into account. Improved fortification is still an issue and can be optimized using the most bioavailable and soluble derivatives. Complete replacement of milk with plant-based drinks without adjusting the overall diet can lead to deficiencies of certain important nutrients in the long term.

Greater protein quality of an egg breakfast may be inadequate to induce satiety during weight loss, compared with a cereal breakfast of equal protein quantity

We compared the effects of consuming egg-breakfast of superior protein quality to cereal-breakfast of similar energy density and protein quantity, but lower protein quality. Two, two-week randomised crossover clinical trials included 30 otherwise healthy women with overweight or obesity. Subjects received counselling to follow a reduced-calorie diet. Under supervision, participants consumed either breakfast for one-week then crossed over to the opposite breakfast. Experiment-1 outcome variables included post-breakfast appetite hormones, glucose and insulin, subjective markers of satiety and energy intake at lunch and dinner. In Experiment-2, an appealing food (brownies) was included in lunch. Following the breakfasts, Experiment-1 showed no significant differences in outcome variables. In Experiment-2, the egg-breakfast increased fullness (p = 0.038), but lunch-time energy intake was not different. If these findings apply to other breakfasts, it suggests that in comparing two breakfasts with similar protein quantity, the greater protein quality of a breakfast may not be adequate to induce satiety.

Acute effects of prior dietary fat ingestion on postprandial metabolic responses to protein and carbohydrate co-ingestion in overweight and obese men: A randomised crossover trial

BACKGROUND

Obesity and insulin resistance are associated with an impaired sensitivity to anabolic stimuli such as dietary protein (anabolic resistance). Omega-3 polyunsaturated fatty acids (n-3 PUFA) may be protective against the deleterious effects of saturated fatty acids (SFA) on insulin resistance. However, the contribution of excess fat consumption to anabolic and insulin resistance and the interaction between SFA and n-3 PUFA is not well studied.

AIM

The primary aim of this study was to investigate the effects of an oral fat pre-load, with or without the partial substitution of SFA with fish oil (FO)-derived n-3 PUFA, on indices of insulin and anabolic sensitivity in response to subsequent dietary protein and carbohydrate (dextrose) co-ingestion.

METHODS

Eight middle-aged males with overweight or obesity (52.8 ± 2.0 yr, BMI 31.8 ± 1.4 kg·m^-2) ingested either an SFA, or isoenergetic SFA and FO emulsion (FO), or water/control (Con), 4 h prior to a bolus of milk protein and dextrose.

RESULTS

Lipid ingestion (in particular FO) impaired the early postprandial uptake of branched chain amino acids (BCAA) into the skeletal muscle in response to protein and dextrose, and attenuated the peak glycaemic response, but was not accompanied by differences in whole body (Matsuda Index: Con: 4.66 ± 0.89, SFA: 5.10 ± 0.94 and FO: 4.07 ± 0.59) or peripheral (forearm glucose _netAUC: Con: 521.7 ± 101.7; SFA: 470.2 ± 125.5 and FO: 495.3 ± 101.6 μmol·min^-1·100 g lean mass·min [t = 240-420 min]) insulin sensitivity between visits. Postprandial whole body fat oxidation was affected by visit (P = 0.024) with elevated rates in SFA and FO, relative to Con (1.85 ± 0.55; 2.19 ± 0.21 and 0.65 ± 0.35 kJ·h^-1·kg^-1 lean body mass, respectively), however muscle uptake of free fatty acids (FFA) was unaffected.

CONCLUSION

Oral lipid preloads, consisting of SFA and FO, impair the early postprandial BCAA uptake into skeletal muscle, which occurs independent of changes in insulin sensitivity.

CLINICAL TRIAL REGISTRY NUMBER

ClinicalTrials.gov Identifier NCT03146286.

Nutritional Regulation of Muscle Stem Cells in Exercise and Disease: The Role of Protein and Amino Acid Dietary Supplementation

Human skeletal muscle is a remarkedly plastic tissue that has a high capacity to adapt in response to various stimuli. These adaptations are due in part to the function of muscle-resident stem/progenitor cells. Skeletal muscle regeneration and adaptation is facilitated by the activation and expansion of muscle stem cells (MuSCs). MuSC fate is regulated by signals released from cells in their niche, such as fibro-adipogenic progenitors (FAPs), as well as a variety of non-cellular niche components. Sufficient dietary protein consumption is critical for maximizing skeletal muscle adaptation to exercise and maintaining skeletal muscle in disease; however, the role of dietary protein in altering MuSC and FAP responses to exercise in healthy populations and skeletal muscle disease states requires more research. The present review provides an overview of this emerging field and suggestions for future directions. The current literature suggests that in response to resistance exercise, protein supplementation has been shown to increase MuSC content and the MuSC response to acute exercise. Similarly, protein supplementation augments the increase in MuSC content following resistance training. Endurance exercise, conversely, is an area of research that is sparse with respect to the interaction of protein supplementation and exercise on muscle stem/progenitor cell fate. Initial evidence suggests that protein supplementation augments the early myogenic response to acute endurance exercise but does not enhance the MuSC response to endurance training. Resistance training increases the number of proliferating FAPs with no additional effect of protein supplementation. Future research should continue to focus on the nutritional regulation of skeletal muscle stem/progenitor cell fate paired with studies examining the effects of exercise on a variety of human populations.

Gut Microbial Stability is Associated with Greater Endurance Performance in Athletes Undertaking Dietary Periodization

Dietary manipulation with high-protein or high-carbohydrate content are frequently employed during elite athletic training, aiming to enhance athletic performance. Such interventions are likely to impact upon gut microbial content. This study explored the impact of acute high-protein or high-carbohydrate diets on measured endurance performance and associated gut microbial community changes. In a cohort of well-matched, highly trained endurance runners, we measured performance outcomes, as well as gut bacterial, viral (FVP), and bacteriophage (IV) communities in a double-blind, repeated-measures design randomized control trial (RCT) to explore the impact of dietary intervention with either high-protein or high-carbohydrate content. High-dietary carbohydrate improved time-trial performance by +6.5% (P < 0.03) and was associated with expansion of Ruminococcus and Collinsella bacterial spp. Conversely, high dietary protein led to a reduction in performance by −23.3% (P = 0.001). This impact was accompanied by significantly reduced diversity (IV: P = 0.04) and altered composition (IV and FVP: P = 0.02) of the gut phageome as well as enrichment of both free and inducible Sk1virus and Leuconostoc bacterial populations. Greatest performance during dietary modification was observed in participants with less substantial shifts in community composition. Gut microbial stability during acute dietary periodization was associated with greater athletic performance in this highly trained, well-matched cohort. Athletes, and those supporting them, should be mindful of the potential consequences of dietary manipulation on gut flora and implications for performance, and periodize appropriately.

IMPORTANCE Dietary periodization is employed to improve endurance exercise performance but may impact on gut microbial communities. Bacteriophage are implicated in bacterial cell homeostasis and have been identified as biomarkers of disequilibrium in the gut ecosystem possibly brought about through dietary periodization. We find high-carbohydrate and high-protein diets to have opposing impacts on endurance performance in highly trained athlete populations. Reduced performance is linked with disturbance of microbial stasis in the gut. We demonstrate bacteriophage communities are the most sensitive component of the gut microbiota to increased gut stress following dietary manipulation. Athletes undertaking dietary periodization should be aware of potential negative impacts of drastic changes to dietary composition on gut microbial stasis and, in turn, endurance performance.

Postoperative Fluid Collections in Total Joint Arthroplasty: A Narrative Review

A post-operative fluid collection (POFC) represents a common finding in both primary and revision total joint arthroplasty (TJA). Fortunately, most resolve on their own, but in instances where they become symptomatic, prompt identification and management are paramount, especially when they occur adjacent to a joint arthroplasty because of the increased the risk of developing a periprosthetic joint infection. A strong clinical suspicion with appropriate clinical exam is required along with select imaging modalities to arrive at a diagnosis. Meticulous surgical technique is crucial to prevent POFC, but new emerging treatments continue to evolve. This article presents an updated overview of incidence, pathophysiology, diagnosis, and management of POFC in the setting of TJA. We review the role of select imaging modalities as well as summarize current literature regarding new treatments such as sclerotherapy agents, acellular dermal matrices, and negative pressure wound therapy. Future studies are necessary to explore the interplay of inflammatory mediators in POFC formation and to define their role in fluid collection resolution.

Dairy as a Source of Iodine and Protein in the UK: Implications for Human Health Across the Life Course, and Future Policy and Research

This narrative review summarizes key concepts in dairy nutrition for supporting human health throughout the life course. Milk and dairy products have been a staple component of our diet for thousands of years and provide a wide range of important nutrients that are otherwise difficult to obtain from dairy-free diets. In this review, we provide a broad perspective on the nutritional roles of iodine and dairy protein in supporting human health during pregnancy and early life, childhood and adolescence, mid- and later-life. New methodologies to identify biomarkers of dairy intake via high-throughput mass spectrometry are discussed, and new concepts such as the role of the food matrix in dairy nutrition are introduced. Finally, future policy and research related to the consumption of dairy and non-dairy alternatives for health are discussed with a view to improving nutritional status across the lifespan.

Perspective: Vegan Diets for Older Adults? A Perspective On the Potential Impact On Muscle Mass and Strength

Consumers are increasingly encouraged to consume more plant-based foods and lower their consumption of foods from animal origin. Concurrently, older adults are recommended to consume an adequate amount of high-quality dietary protein for the prevention of age-related muscle loss. In the current Perspective article, we discuss why it may not be preferred to consume a vegan diet at an older age. Our perspective is based on the proposed lower bioavailability and functionality of proteins in a vegan diet due to the matrix of the whole-food protein sources, the lower essential amino acid (EAA) content, and specific EAA deficiencies in proteins derived from plant-based foods. We propose that a vegan diet increases the risk of an inadequate protein intake at an older age and that current strategies to improve the anabolic properties of plant-based foods are not feasible for many older adults. We provide recommendations for further research to substantiate the remaining knowledge gaps regarding the consequences of a vegan diet on skeletal muscle mass and strength at an older age.

The contributory role of vascular health in age-related anabolic resistance

Sarcopenia, or the age-related loss of skeletal muscle mass and function, is an increasingly prevalent condition that contributes to reduced quality of life, morbidity, and mortality in older adults. Older adults display blunted anabolic responses to otherwise anabolic stimuli-a phenomenon that has been termed anabolic resistance (AR)-which is likely a casual factor in sarcopenia development. AR is multifaceted, but historically much of the mechanistic focus has been on signalling impairments, and less focus has been placed on the role of the vasculature in postprandial protein kinetics. The vascular endothelium plays an indispensable role in regulating vascular tone and blood flow, and age-related impairments in vascular health may impede nutrient-stimulated vasodilation and subsequently the ability to deliver nutrients (e.g. amino acids) to skeletal muscle. Although the majority of data has been obtained studying younger adults, the relatively limited data on the effect of blood flow on protein kinetics in older adults suggest that vasodilatory function, especially of the microvasculature, strongly influences the muscle protein synthetic response to amino acid feedings. In this narrative review, we examine evidence of AR in older adults following amino acid and mixed meal consumption, examine the evidence linking vascular dysfunction and insulin resistance to age-related AR, review the influence of nitric oxide and endothelin-1 on age-related vascular dysfunction as it relates to AR, briefly review the potential causal role of arterial stiffness in promoting skeletal muscle microvascular dysfunction and AR, and provide a brief overview and future considerations for research examining age-related AR.

Legumes as basic ingredients in the production of dairy-free cheese alternatives: a review

Research into dairy-free alternative products, whether plant-based or cell-based, is growing fast and the food industry is facing a new challenge of creating innovative, nutritious, accessible, and natural dairy-free cheese alternatives. The market demand for these products is continuing to increase owing to more people choosing to reduce or eliminate meat and dairy products from their diet for health, environmental sustainability, and/or ethical reasons. This review investigates the current status of dairy product alternatives. Legume proteins have good technological properties and are cheap, which gives them a strong commercial potential to be used in plant-based cheese-like products. However, few legume proteins have been explored in the formulation, development, and manufacture of a fully dairy-free cheese because of their undesirable properties: heat stable anti-nutritional factors and a beany flavor. These can be alleviated by novel or traditional and economical techniques. The improvement and diversification of the formulation of legume-based cheese alternatives is strongly suggested as a low-cost step towards more sustainable food chains. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Clinician Impact on Athlete Recovery and Readiness in a 24-Hour Training Cycle

This paper explores a 24-hr training cycle and how clinicians contribute to an athlete’s transition from recovery to readiness. The cycle is divided into three phases: immediate, intermediate, and extended. Phase break down is meant to provide wellness prioritization for the athlete and how the clinician can facilitate sustainable performance during a competitive season.

Strategies to Prevent Sarcopenia in the Aging Process: Role of Protein Intake and Exercise

Sarcopenia is one of the main issues associated with the process of aging. Characterized by muscle mass loss, it is triggered by several conditions, including sedentary habits and negative net protein balance. According to World Health Organization, it is expected a 38% increase in older individuals by 2025. Therefore, it is noteworthy to establish recommendations to prevent sarcopenia and several events and comorbidities associated with this health issue condition. In this review, we discuss the role of these factors, prevention strategies, and recommendations, with a focus on protein intake and exercise.

The role of holistic nutritional properties of diets in the assessment of food system and dietary sustainability

Advancing sustainable diets for nutrition security and sustainable development necessitates clear nutrition metrics for measuring nutritional quality of diets. Food composition, nutrient requirements, and dietary intake are among the most common nutrition metrics used in the current assessment of sustainable diets. Broadly, most studies in the area classify animal-source foods (ASF) as having a substantially higher environmental footprint in comparison to plant-source foods (PSF). As a result, much of the current dietary advice promulgates diets containing higher proportions of PSF. However, this generalization is misleading since most of these studies do not distinguish between the gross and bioavailable nutrient fractions in mixed human diets. The bioavailability of essential nutrients including β-carotene, vitamin B-12, iron, zinc, calcium, and indispensable amino acids varies greatly across different diets. The failure to consider bioavailability in sustainability measurements undermines the complementary role that ASF play in achieving nutrition security in vulnerable populations. This article critically reviews the scientific evidence on the holistic nutritional quality of diets and identifies methodological problems that exist in the way the nutritional quality of diets is measured. Finally, we discuss the importance of developing nutrient bioavailability as a requisite nutrition metric to contextualize the environmental impacts of different diets.

Fueling Gut Microbes: A Review of the Interaction between Diet, Exercise, and the Gut Microbiota in Athletes

The athlete's goal is to optimize their performance. Towards this end, nutrition has been used to improve the health of athletes' brains, bones, muscles, and cardiovascular system. However, recent research suggests that the gut and its resident microbiota may also play a role in athlete health and performance. Therefore, athletes should consider dietary strategies in the context of their potential effects on the gut microbiota, including the impact of sports-centric dietary strategies (e.g., protein supplements, carbohydrate loading) on the gut microbiota as well as the effects of gut-centric dietary strategies (e.g., probiotics, prebiotics) on performance. This review provides an overview of the interaction between diet, exercise, and the gut microbiota, focusing on dietary strategies that may impact both the gut microbiota and athletic performance. Current evidence suggests that the gut microbiota could, in theory, contribute to the effects of dietary intake on athletic performance by influencing microbial metabolite production, gastrointestinal physiology, and immune modulation. Common dietary strategies such as high protein and simple carbohydrate intake, low fiber intake, and food avoidance may adversely impact the gut microbiota and, in turn, performance. Conversely, intake of adequate dietary fiber, a variety of protein sources, and emphasis on unsaturated fats, especially omega-3 (ɷ-3) fatty acids, in addition to consumption of prebiotics, probiotics, and synbiotics, have shown promising results in optimizing athlete health and performance. Ultimately, while this is an emerging and promising area of research, more studies are needed that incorporate, control, and manipulate all 3 of these elements (i.e., diet, exercise, and gut microbiome) to provide recommendations for athletes on how to "fuel their microbes."

Physiological Limitations of Protein Foods Ounce Equivalents and the Underappreciated Role of Essential Amino Acid Density in Healthy Dietary Patterns

Protein quality is an important component of protein intake to support growth, development, and maintenance of essential body tissues and functions. Therefore, protein quality should be emphasized as a key characteristic during protein food selection within the larger context of healthy dietary patterns, especially when considering the wide variance of protein quality across animal- and plant-based foods. However, the USDA Dietary Guidelines for Americans (DGA) do not address specific protein quality recommendations within their protein foods ounce equivalents guidance or as a component of Healthy U.S. Style, Healthy Vegetarian, and Healthy Mediterranean Style dietary patterns. In addition, the protein foods ounce equivalents within the DGA are not established on any obvious metabolic equivalency characteristic [i.e., energy, protein, or essential amino acid (EAA) content], which creates misleading messaging of equivalent functional and metabolic benefit across protein foods. EAA content is a key characteristic of protein quality and can be a practical focal point for protein intake recommendations and achieving healthy dietary patterns. This review discusses the importance of protein quality, the state of messaging within DGA recommendations, and proposes EAA density (i.e., EAA content relative to total energy) as one practical approach to improve current dietary recommendations. Two recent publications that evaluated the DGA protein foods ounce equivalents based on metabolic effect and their application within DGA recommended dietary patterns are discussed.

Older Adults' Knowledge and Perceptions of Whole Foods as an Exercise Recovery Strategy

Resistance exercise is a widely advocated treatment for improving muscle strength and performance in older adults. Maximizing the benefit of resistance exercise by ensuring optimal recovery is an important aim and studies are now seeking interventions to expedite exercise recovery in older people. A recovery strategy that has acquired considerable interest is the consumption of protein, and more recently, the consumption of protein-rich whole foods. This study aimed to understand the perspectives of community-dwelling older adults, and determine their knowledge of exercise recovery strategies, their preferences for recovery strategies, and their attitudes toward using whole foods, such as milk as a post-exercise recovery aid. Two hundred ninety-one older adults (74 ± 4 years) were recruited to complete a self-administered online survey. A mixed methods approach was used to gather in-depth data from the cohort. Participants were asked to complete a combination of free-text (open-ended) and multiple-choice questions. Content analysis was conducted on responses to open-ended questions through a systematic classification process of coding. The most common recovery strategies reported were heat treatment, rest, and massage. Nutrition was rarely cited as a recovery strategy. Less than 2% of respondents mentioned nutrition, of these, only half mentioned a protein source. Forty-nine percent expressed negative opinions toward recovery supplements (e.g., “waste of money”) compared to 7% expressing positive opinions. Whole foods such as milk, meat, fish, and fruit, were deemed to be a more acceptable recovery strategy than supplements by 80% of respondents. Those that found whole foods to be equally as acceptable (18%), cited efficacy as their main concern, and those that declared whole foods less acceptable (2%) had no common reason. Despite the high acceptability of whole foods, only 35% were aware that these foods could aid recovery. When asked about milk specifically, the majority of older adults (73%) said this would, or might, be an acceptable exercise recovery strategy. Those that found milk an unacceptable recovery strategy (27%) often cited disliking milk or an allergy/intolerance. In conclusion, whilst whole foods represented an acceptable recovery intervention for older adults, the majority were unaware of the potential benefits of nutrition for post-exercise recovery.

Protein Requirements for Master Athletes: Just Older Versions of Their Younger Selves

It is established that protein requirements are elevated in athletes to support their training and post-exercise recovery and adaptation, especially within skeletal muscle. However, research on the requirements for this macronutrient has been performed almost exclusively in younger athletes, which may complicate their translation to the growing population of Master athletes (i.e. > 35 years old). In contrast to older (> 65 years) untrained adults who typically demonstrate anabolic resistance to dietary protein as a primary mediator of the ‘normal’ age-related loss of muscle mass and strength, Master athletes are generally considered successful models of aging as evidenced by possessing similar body composition, muscle mass, and aerobic fitness as untrained adults more than half their age. The primary physiology changes considered to underpin the anabolic resistance of aging are precipitated or exacerbated by physical inactivity, which has led to higher protein recommendations to stimulate muscle protein synthesis in older untrained compared to younger untrained adults. This review puts forth the argument that Master athletes have similar muscle characteristics, physiological responses to exercise, and protein metabolism as young athletes and, therefore, are unlikely to have protein requirements that are different from their young contemporaries. Recommendations for protein amount, type, and pattern will be discussed for Master athletes to enhance their recovery from and adaptation to resistance and endurance training.

Evaluating the Leucine Trigger Hypothesis to Explain the Post-prandial Regulation of Muscle Protein Synthesis in Young and Older Adults: A Systematic Review

Background: The "leucine trigger" hypothesis was originally conceived to explain the post-prandial regulation of muscle protein synthesis (MPS). This hypothesis implicates the magnitude (amplitude and rate) of post-prandial increase in blood leucine concentrations for regulation of the magnitude of MPS response to an ingested protein source. Recent evidence from experimental studies has challenged this theory, with reports of a disconnect between blood leucine concentration profiles and post-prandial rates of MPS in response to protein ingestion. Aim: The primary aim of this systematic review was to qualitatively evaluate the leucine trigger hypothesis to explain the post-prandial regulation of MPS in response to ingested protein at rest and post-exercise in young and older adults. We hypothesized that experimental support for the leucine trigger hypothesis will depend on age, exercise status (rest vs. post-exercise), and type of ingested protein (i.e., isolated proteins vs. protein-rich whole food sources). Methods: This qualitative systematic review extracted data from studies that combined measurements of post-prandial blood leucine concentrations and rates of MPS following ingested protein at rest and following exercise in young and older adults. Data relating to blood leucine concentration profiles and post-prandial MPS rates were extracted from all studies, and reported as providing sufficient or insufficient evidence for the leucine trigger hypothesis. Results: Overall, 16 of the 29 eligible studies provided sufficient evidence to support the leucine trigger hypothesis for explaining divergent post-prandial rates of MPS in response to different ingested protein sources. Of these 16 studies, 13 were conducted in older adults (eight of which conducted measurements post-exercise) and 14 studies included the administration of isolated proteins. Conclusion: This systematic review underscores the merits of the leucine trigger hypothesis for the explanation of the regulation of MPS. However, our data indicate that the leucine trigger hypothesis confers most application in regulating the post-prandial response of MPS to ingested proteins in older adults. Consistent with our hypothesis, we provide data to support the idea that the leucine trigger hypothesis is more relevant within the context of ingesting isolated protein sources rather than protein-rich whole foods. Future mechanistic studies are warranted to understand the complex series of modulatory factors beyond blood leucine concentration profiles within a food matrix that regulate post-prandial rates of MPS.

Fuelling the female athlete: Carbohydrate and protein recommendations

Optimal carbohydrate and protein intakes are vital for modulating training adaptation, recovery, and exercise performance. However, the research base underpinning contemporary sport nutrition guidelines has largely been conducted in male populations with a lack of consensus on whether the menstrual phase and associated changes in sex hormones allow broad application of these principles to female athletes. The present review will summarise our current understanding of carbohydrate and protein requirements in female athletes across the menstrual cycle and provide a critical analysis on how they compare to male athletes. On the basis of current evidence, we consider it premature to conclude that female athletes require sex specific guidelines in relation to CHO or protein requirements provided energy needs are met. However, there is a need for further research using sport-specific competition and training related exercise protocols that rigorously control for prior exercise, CHO/energy intake, contraceptive use and phase of menstrual cycle. Our overarching recommendation is to use current recommendations as a basis for adopting an individualised approach that takes into account athlete specific training and competition goals whilst also considering personal symptoms associated with the menstrual cycle.

Anabolic Resistance of Muscle Protein Turnover Comes in Various Shapes and Sizes

Anabolic resistance is defined by a blunted stimulation of muscle protein synthesis rates (MPS) to common anabolic stimuli in skeletal muscle tissue such as dietary protein and exercise. Generally, MPS is the target of most exercise and feeding interventions as muscle protein breakdown rates seem to be less responsive to these stimuli. Ultimately, the blunted responsiveness of MPS to dietary protein and exercise underpins the loss of the amount and quality of skeletal muscle mass leading to decrements in physical performance in these populations. The increase of both habitual physical activity (including structured exercise that targets general fitness characteristics) and protein dense food ingestion are frontline strategies utilized to support muscle mass, performance, and health. In this paper, we discuss anabolic resistance as a common denominator underpinning muscle mass loss with aging, obesity, and other disease states. Namely, we discuss the fact that anabolic resistance exists as a dimmer switch, capable of varying from higher to lower levels of resistance, to the main anabolic stimuli of feeding and exercise depending on the population. Moreover, we review the evidence on whether increased physical activity and targeted exercise can be leveraged to restore the sensitivity of skeletal muscle tissue to dietary amino acids regardless of the population.

Nutrition for Older Athletes: Focus on Sex-Differences

Regular physical exercise and a healthy diet are major determinants of a healthy lifespan. Although aging is associated with declining endurance performance and muscle function, these components can favorably be modified by regular physical activity and especially by exercise training at all ages in both sexes. In addition, age-related changes in body composition and metabolism, which affect even highly trained masters athletes, can in part be compensated for by higher exercise metabolic efficiency in active individuals. Accordingly, masters athletes are often considered as a role model for healthy aging and their physical capacities are an impressive example of what is possible in aging individuals. In the present review, we first discuss physiological changes, performance and trainability of older athletes with a focus on sex differences. Second, we describe the most important hormonal alterations occurring during aging pertaining regulation of appetite, glucose homeostasis and energy expenditure and the modulatory role of exercise training. The third part highlights nutritional aspects that may support health and physical performance for older athletes. Key nutrition-related concerns include the need for adequate energy and protein intake for preventing low bone and muscle mass and a higher demand for specific nutrients (e.g., vitamin D and probiotics) that may reduce the infection burden in masters athletes. Fourth, we present important research findings on the association between exercise, nutrition and the microbiota, which represents a rapidly developing field in sports nutrition.

The role of protein hydrolysates for exercise-induced skeletal muscle recovery and adaptation: a current perspective

The protein supplement industry is expanding rapidly and estimated to have a multi-billion market worth. Recent research has centred on understanding how the manufacturing processes of protein supplements may impact muscle recovery and remodeling. The hydrolysed forms of protein undergo a further heating extraction process during production which may contribute to amino acids (AA) appearing in circulation at a slightly quicker rate, or greater amplitude, than the intact form. Whilst the relative significance of the rate of aminoacidemia to muscle protein synthesis is debated, it has been suggested that protein hydrolysates, potentially through the more rapid delivery and higher proportion of di-, tri- and smaller oligo-peptides into circulation, are superior to intact non-hydrolysed proteins and free AAs in promoting skeletal muscle protein remodeling and recovery. However, despite these claims, there is currently insufficient evidence to support superior muscle anabolic properties compared with intact non-hydrolysed proteins and/or free AA controls. Further research is warranted with appropriate protein controls, particularly in populations consuming insufficient amounts of protein, to support and/or refute an important muscle anabolic role of protein hydrolysates. The primary purpose of this review is to provide the reader with a current perspective on the potential anabolic effects of protein hydrolysates in individuals wishing to optimise recovery from, and maximise adaptation to, exercise training.

Protein Source and Quality for Skeletal Muscle Anabolism in Young and Older Adults: A Systematic Review and Meta-Analysis

BACKGROUND

There is much debate regarding the source/quality of dietary proteins in supporting indices of skeletal muscle anabolism.

OBJECTIVE

We performed a systematic review and meta-analysis to determine the effect of protein source/quality on acute muscle protein synthesis (MPS) and changes in lean body mass (LBM) and strength, when combined with resistance exercise (RE).

METHODS

A systematic search of the literature was conducted to identify studies that compared the effects of ≥2 dose-matched, predominantly isolated protein sources of varying "quality." Three separate models were employed as follows: 1) protein feeding alone on MPS, 2) protein feeding combined with a bout of RE on MPS, and 3) protein feeding combined with longer-term resistance exercise training (RET) on LBM and strength. Further subgroup analyses were performed to compare the effects of protein source/quality between young and older adults. A total of 27 studies in young (18-35 y) and older (≥60 y) adults were included.

RESULTS

Analysis revealed an effect favoring higher-quality protein for postprandial MPS at rest [mean difference (MD): 0.014%/h; 95% CI: 0.006, 0.021; P < 0.001] and following RE (MD: 0.022%/h; 95% CI: 0.014, 0.030; P < 0.00001) in young (model 1: 0.016%/h; 95% CI: -0.004, 0.036; P = 0.12; model 2: 0.030%/h; 95% CI: 0.015, 0.045; P < 0.0001) and older (model 1: 0.012%/h; 95% CI: 0.006, 0.018; P < 0.001; model 2: 0.014%/h; 95% CI: 0.007, 0.021; P < 0.001) adults. However, although higher protein quality was associated with superior strength gains with RET [standardized mean difference (SMD): 0.24 kg; 95% CI: 0.02, 0.45; P = 0.03)], no effect was observed on changes to LBM (SMD: 0.05 kg; 95% CI: -0.16, 0.25; P = 0.65).

CONCLUSIONS

The current review suggests that protein quality may provide a small but significant impact on indices of muscle protein anabolism in young and older adults. However, further research is warranted to elucidate the importance of protein source/quality on musculoskeletal aging, particularly in situations of low protein intake.

Increased Leg Strength After Concurrent Aerobic and Resistance Exercise Training in Older Adults Is Augmented by a Whole Food-Based High Protein Diet Intervention

Most studies in older adults have utilized powdered protein supplements or oral nutrition solutions as a source of additional dietary protein, but whole foods may provide a greater anabolic stimulus than protein isolated from food matrices. Therefore, the present study investigated a concurrent aerobic and resistance exercise training program in older adults, in the absence or presence of a high protein whole food-based dietary intervention, for effects on strength, physical function, and body composition. Community-dwelling older adults (n = 56; M/F, 28/28; age, 69.3 ± 4.0 years; BMI, 26.6 ± 3.7 kg m⁻²) participated in a 12-week intervention after randomization to either nutrition only (NUTR; n = 16), exercise only (EX, n = 19), or nutrition plus exercise (NUTR + EX, n = 21) groups. NUTR and NUTR + EX followed a dietary intervention targeting an increase in protein-rich meals at breakfast, lunch, and dinner. Exercise training in EX and NUTR + EX consisted of 24 min sessions of concurrent aerobic and resistance exercise performed three times per week. Daily protein intake increased in NUTR and NUTR + EX, but not EX. The increase in 1RM leg press strength was greater (Interaction effect, P = 0.012) in NUTR + EX [29.6 (18.1, 41.0) kg] than increases observed in NUTR [11.1 (−1.3, 23.6) kg] and EX [12.3 (0.9, 23.8) kg]. The increase in 1RM chest press strength was greater (interaction effect, P = 0.031) in NUTR + EX [6.3 (4.0, 8.6) kg] than the increase observed in NUTR [2.9 (0.3, 5.5) kg], but not EX [6.3 (3.9, 8.7) kg]. Hand-grip strength and sit-to-stand performance were each improved in all three groups, with no differences observed between groups (interaction effect, P = 0.382 and P = 0.671, respectively). An increase in percentage body fat was observed in NUTR, but not in EX or NUTR + EX (interaction effect, P = 0.018). No between-group differences were observed for change in lean body mass (interaction effect, P = 0.402). Concurrent aerobic and resistance exercise training improves strength and physical function in older adults, but combining this training with an increase in daily protein intake through whole foods may be advantageous to increase lower limb strength.

Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review

Branched-chain amino acids (BCAA) are one of the most popular sports supplements, marketed under the premise that they enhance muscular adaptations. Despite their prevalent consumption among athletes and the general public, the efficacy of BCAA has been an ongoing source of controversy in the sports nutrition field. Early support for BCAA supplementation was derived from extrapolation of mechanistic data on their role in muscle protein metabolism. Of the three BCAA, leucine has received the most attention because of its ability to stimulate the initial acute anabolic response. However, a substantial body of both acute and longitudinal research has now accumulated on the topic, affording the ability to scrutinize the effects of BCAA and leucine from a practical standpoint. This article aims to critically review the current literature and draw evidence-based conclusions about the putative benefits of BCAA or leucine supplementation on muscle strength and hypertrophy as well as illuminate gaps in the literature that warrant future study.

The Effects of a High-Protein Dairy Milk Beverage With or Without Progressive Resistance Training on Fat-Free Mass, Skeletal Muscle Strength and Power, and Functional Performance in Healthy Active Older Adults: A 12-Week Randomized Controlled Trial

The study aimed to investigate the independent and combined effects of consuming a high-protein dairy milk beverage, twice daily, with or without a progressive resistance training (PRT) program on outcomes of age-related sarcopenia, in healthy active older (≥50 years) adults. In this 12-week, 2 × 2 factorial study, participants were randomly allocated into one of four groups: dairy milk beverage (DM), exercise and dairy milk beverage (EX+DM), exercise alone (EX), and control (CON). The EX group underwent a 12-week whole-body PRT schedule (three sessions/week) and a high-protein dairy milk beverage (DM) was consumed twice daily (30 g protein/day). At weeks 0, 6, and 12, body composition (iDXA), strength [one-repetition maximum (1RM): leg press, chest press, lateral (lat) pull-down, and handgrip], power (countermovement jump), cardiorespiratory fitness (VO2), and physical performance (gait speed) were measured. Before measurements, blood samples were collected to determine the immune (i.e., leukocyte trafficking and inflammatory cytokines) and hormonal (i.e., insulin, cortisol, IGF-1, testosterone, and estradiol) profiles. Participants (n = 37) completed the study within the controlled experimental conditions. Protein intake increased in the EX+DM [mean ± SD, 1.2 ± 0.2 to 1.8 ± 0.4 g/kg body mass (BM) per day-1] and DM (1.3 ± 0.5 to 1.8 ± 0.6 g kg-1 BM day-1) groups during the intervention. Absolute fat-free mass increased in the EX+DM [mean (95% confidence interval) = 0.65 (0.25-1.0) kg] and EX [0.49 (-0.44 to 1.40) kg] groups (P < 0.001) compared to DM [-0.54 (-1.6 to 0.05) kg]. Relative fat mass decreased (group*time, P = 0.018) in DM [-1.8% (-3.3 to -0.35%)] and EX+DM [-1.3% (-2.3 to -0.31%)], which was a greater reduction than that in the CON [0.10% (-0.80 to 1.0%)] group (P < 0.01). Relative maximal strength increased in both the EX and EX+DM (≥35%, P < 0.05) groups, but not in the DM and CON groups. The change in 1RM strength outcomes was higher in EX+DM compared to all other groups (53-78%, P < 0.01). There was an increase in resting plasma IL-10 concentration in EX+DM (88%), compared to all the other groups (P = 0.016). No other differences in systemic inflammatory cytokines were observed. There were no significant changes in all hormone concentrations measured among all groups. In conclusion, a high-protein dairy milk beverage providing additional protein did not further enhance the effects of PRT on outcomes of fat-free mass, power, or physical performance. However, there was a significant augmentative effect for high-protein dairy milk consumption on changes to maximal strength outcomes during PRT in healthy active older adults.

Protein Source and Muscle Health in Older Adults: A Literature Review

Research shows that higher dietary protein of up to 1.2 g/kg_bodyweight/day may help prevent sarcopenia and maintain musculoskeletal health in older individuals. Achieving higher daily dietary protein levels is challenging, particularly for older adults with declining appetites and underlying health conditions. The negative impact of these limitations on aging muscle may be circumvented through the consumption of high-quality sources of protein and/or supplementation. Currently, there is a debate regarding whether source of protein differentially affects musculoskeletal health in older adults. Whey and soy protein have been used as the most common high-quality proteins in recent literature. However, there is growing consumer demand for additional plant-sourced dietary protein options. For example, pea protein is rapidly gaining popularity among consumers, despite little to no research regarding its long-term impact on muscle health. Therefore, the objectives of this review are to: (1) review current literature from the past decade evaluating whether specific source(s) of dietary protein provide maximum benefit to muscle health in older adults; and (2) highlight the need for future research specific to underrepresented plant protein sources, such as pea protein, to then provide clearer messaging surrounding plant-sourced versus animal-sourced protein and their effects on the aging musculoskeletal system.

Acute Effects of Cheddar Cheese Consumption on Circulating Amino Acids and Human Skeletal Muscle

Cheddar cheese is a protein-dense whole food and high in leucine content. However, no information is known about the acute blood amino acid kinetics and protein anabolic effects in skeletal muscle in healthy adults. Therefore, we conducted a crossover study in which men and women (n = 24; ~27 years, ~23 kg/m2) consumed cheese (20 g protein) or an isonitrogenous amount of milk. Blood and skeletal muscle biopsies were taken before and during the post absorptive period following ingestion. We evaluated circulating essential and non-essential amino acids, insulin, and free fatty acids and examined skeletal muscle anabolism by mTORC1 cellular localization, intracellular signaling, and ribosomal profiling. We found that cheese ingestion had a slower yet more sustained branched-chain amino acid circulation appearance over the postprandial period peaking at ~120 min. Cheese also modestly stimulated mTORC1 signaling and increased membrane localization. Using ribosomal profiling we found that, though both milk and cheese stimulated a muscle anabolic program associated with mTORC1 signaling that was more evident with milk, mTORC1 signaling persisted with cheese while also inducing a lower insulinogenic response. We conclude that Cheddar cheese induced a sustained blood amino acid and moderate muscle mTORC1 response yet had a lower glycemic profile compared to milk.

Limitations with the Digestible Indispensable Amino Acid Score (DIAAS) with Special Attention to Plant-Based Diets: a Review

PURPOSE OF REVIEW

This review describes several limitations of the Digestible Indispensable Amino Acid Score (DIAAS) with a focus on its application to plant-based dietary patterns.

RECENT FINDINGS

Evaluating protein quality in terms of digestibility is paramount to support and optimize the health and well-being of human populations in situations where food insecurity and protein energy malnutrition are widespread. The Food and Agriculture Organization (FAO) of the United Nations has endorsed the DIAAS to replace the previously recommended Protein Digestibility Corrected Amino Acid Score (PDCAAS) for protein quality assessment. While multiple strengths characterize the DIAAS, substantial limitations remain, many of which are accentuated in the context of a plant-based dietary pattern. Some of these limitations include a failure to translate differences in nitrogen-to-protein conversion factors between plant- and animal-based foods, limited representation of commonly consumed plant-based foods within the scoring framework, inadequate recognition of the increased digestibility of commonly consumed heat-treated and processed plant-based foods, its formulation centered on fast-growing animal models rather than humans, and a focus on individual isolated foods vs the food matrix. The DIAAS is also increasingly being used out of context where its application could produce erroneous results such as exercise settings. When investigating protein quality, particularly in a plant-based dietary context, the DIAAS should ideally be avoided.

The effects of resistance training with or without peanut protein supplementation on skeletal muscle and strength adaptations in older individuals

Several studies suggest resistance training (RT) while supplementing with various protein supplements can enhance strength and muscle mass in older individuals. However, to date, no study has examined the effects of RT with a peanut protein powder (PP) supplement on these outcomes. Herein, 39 older, untrained individuals (n = 17 female, n = 22 male; age = 58.6 ± 8.0 years; body mass index =28.7 ± 5.8) completed a 6-week (n = 22) or 10-week (n = 17) RT program, where full-body training was implemented twice weekly (ClinicalTrials.gov trial registration NCT04015479; registered July 11, 2019). Participants in each program were randomly assigned to consume either a PP supplement once per day (75 total g powder providing 30 g protein, > 9.2 g essential amino acids, ~ 315 kcal; n = 20) or no supplement (CTL; n = 19). Right leg vastus lateralis (VL) muscle biopsies were obtained prior to and 24 h following the first training bout in all participants to assess the change in myofibrillar protein synthetic rates (MyoPS) as measured via the deuterium-oxide (D₂O) tracer method. Pre- and Post-intervention testing in all participants was conducted using dual energy x-ray absorptiometry (DXA), VL ultrasound imaging, a peripheral quantitative computed tomography (pQCT) scan at the mid-thigh, and right leg isokinetic dynamometer assessments. Integrated MyoPS rates over a 24-h period were not significantly different (p < 0.05) between supplement groups following the first training bout. Regarding chronic changes, there were no significant supplement-by-time interactions in DXA-derived fat mass, lean soft tissue mass or percent body fat between supplementation groups. There was, however, a significant increase in VL thickness in PP versus CTL participants when the 6- and 10-week cohorts were pooled (interaction p = 0.041). There was also a significant increase in knee flexion torque in the 10-week PP group versus the CTL group (interaction p = 0.032). In conclusion, a higher-protein, defatted peanut powder supplement in combination with RT positively affects select markers of muscle hypertrophy and strength in an untrained, older adult population. Moreover, subanalyses indicated that gender did not play a role in these adaptations.