A Moderate Serving of High-Quality Protein Maximally Stimulates Skeletal Muscle Protein Synthesis in Young and Elderly Subjects

doi:10.1016/j.jada.2009.06.369

Journal of the American Dietetic Association

Volume 109, Issue 9, September 2009, Pages 1582-1586

https://doi.org/10.1016/j.jada.2009.06.369 Get rights and content

Abstract

Ingestion of sufficient dietary protein is a fundamental prerequisite for muscle protein synthesis and maintenance of muscle mass and function. Elderly people are often at increased risk for protein-energy malnutrition, sarcopenia, and a diminished quality of life. This study sought to compare changes in muscle protein synthesis and anabolic efficiency in response to a single moderate serving (113 g; 220 kcal; 30 g protein) or large serving (340 g; 660 kcal; 90 g protein) of 90% lean beef. Venous blood and vastus lateralis muscle biopsy samples were obtained during a primed, constant infusion (0.08 μmol/kg/min) of L-[ring-¹³C₆] phenylalanine in healthy young (n=17; 34±3 years) and elderly (n=17; 68±2 years) individuals. Mixed muscle fractional synthesis rate was calculated during a 3-hour postabsorptive period and for 5 hours after meal ingestion. Data were analyzed using a two-way repeated measures analysis of variance with Tukey's pairwise comparisons. A 113-g serving of lean beef increased muscle protein synthesis by approximately 50% in both young and older volunteers. Despite a threefold increase in protein and energy content, there was no further increase in protein synthesis after ingestion of 340 g lean beef in either age group. Ingestion of more than 30 g protein in a single meal does not further enhance the stimulation of muscle protein synthesis in young and elderly.

Section snippets

Subjects and Experimental Design

Participants were recruited through the Sealy Center on Aging Volunteer Registry at The University of Texas Medical Branch and through newspaper advertisements and flyers. This study was approved by the Institutional Review Board at The University of Texas Medical Branch. An independent, internal monitoring board oversaw study procedures, data collection, and analysis.

Medical screening included a medical history and physical, blood count, plasma electrolytes, blood glucose concentration, and

Results and Discussion

Fasting plasma phenylalanine enrichments (tracer/tracee ratio) were similar in the moderate-protein group (young, 0.112±0.003; elderly, 0.113±0.002) and high-protein group (young, 0.101±0.008; elderly, 0.113±0.002) (P>0.05). After meal ingestion there was an expected dilution of the labeled plasma phenylalanine pool. Mean postprandial enrichment values in the moderate-protein group (113 g beef) were 0.105±0.002 (young) and 0.105±0.004 (elderly) (P>0.05), whereas enrichment values in the

T. B. Symons is an assistant professor, Graduate Center for Gerontology, University of Kentucky, Lexington; at the time of the study, he was a postdoctoral fellow, Division of Rehabilitation Sciences, The University of Texas Medical Branch, Galveston.

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Daily dietary protein distribution at a fixed protein level does not appear to influence changes in body composition during weight loss in women of reproductive age.
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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.
Important Concepts in Protein Nutrition, Aging, and Skeletal Muscle: Honoring Dr Douglas Paddon-Jones (1969–2021) by Highlighting His Research Contributions
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This review is a tribute to honor Dr Douglas Paddon-Jones by highlighting his career research contributions. Dr Paddon-Jones was a leader in recognizing the importance of muscle health and the interactions of physical activity and dietary protein for optimizing the health span. Aging is characterized by loss of muscle mass and strength associated with reduced rates of muscle protein synthesis (MPS) and the ability to repair and replace muscle proteins. Research from the team at the University of Texas Medical Branch in Galveston discovered that the age-related decline in MPS could be overcome by increasing the quantity or quality of dietary protein at each meal. Dr Paddon-Jones was instrumental in proposing and testing a “protein threshold” of ∼30 g protein/meal to optimize MPS in older adults. Dr Paddon-Jones demonstrated that physical inactivity greatly accelerates the loss of muscle mass and function in older adults. His work in physical activity led him to propose the “Catabolic Crisis Model” of muscle size and function losses, suggesting that age-related muscle loss is not a linear process, but the result of acute periods of disuse associated with injuries, illnesses, and bed rest. This model creates the opportunity to provide targeted interventions via protein supplementation and/or increased dietary protein through consuming high-quality animal-source foods. He illustrated that nutritional support, particularly enhanced protein quantity, quality, and meal distribution, can help preserve muscle health during periods of inactivity and promote health across the life course.
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Humans have been consuming animal products since time immemorial. Some of the major turning points in human evolution have been directly linked to the choice of food consumed. Even in the modern world, animal and aquatic protein sources such as meat, milk, eggs, and fish continue to provide all the essential macro- and micronutrients required for optimal growth and development. Meat is a high biological value protein source providing the nine essential amino acids required for growth as well as being a good source of Vitamin B₁₂. Milk and eggs are also great sources of protein due to their high protein digestibility and a good amino acid profile. Regular egg consumption leads to an increase in skeletal muscle mass. Fish is particularly a good source of long-chain omega-3 polyunsaturated fatty acids. Studies have confirmed that consumption of these protein sources is safe and can provide most of a person’s nutritional needs when consumed in the recommended amounts as part of a regular diet.
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This single-arm observational study explored the feasibility and efficacy of a 12-week personalised physical activity and dietary protein intervention programme for older adults undergoing peritoneal dialysis. Older adults undergoing peritoneal dialysis received eight individualised nutrition and physical activity advice sessions provided by trained nurses. Protein intake and physical activity were regarded as primary outcomes. All data were collected at baseline and at week 12. The enrolment rate was 78.4%. Twenty-nine patients participated in the study. Of these, 86.2% (25/29) completed the intervention. There was a significant increase in protein intake (t = -4.453, P< 0.001) and physical activity levels (Z = -2.929, P = 0.004). Of the participants, 56.0% achieved the targeted protein goal, and 41.4% met the physical activity goal. The timed up-and-go performance (t = 4.135, P = 0.001) increased after intervention. Trained nurses can successfully implement personalised diet and physical activity advice, and achieve promising patient outcomes.
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To consider the evidence for sex-specific nutrition requirements to optimise the health and performance of military personnel.
Narrative review.
Published literature was reviewed, with a focus on sex-specific requirements, in the following areas: nutrition for optimising muscle mass and function, nutrition during energy deficit, and nutrition for reproductive and bone health.
There are limited data on sex differences in protein requirements but extant data suggest that, despite less muscle mass, on average, in women, sex-specific protein feeding strategies are not required to optimise muscle mass in military-aged individuals. Similarly, despite sex differences in metabolic and endocrine responses to energy deficit, current data do not suggest a requirement for sex-specific feeding strategies during energy deficit. Energy deficit impairs health and performance, most notably bone and reproductive health and these impairments are greater for women. Vitamin D, iron and calcium are important nutrients to protect the bone health of female military personnel due to increased risk of stress fracture.
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M. Sheffield-Moore is an associate professor, Department of Internal Medicine, The University of Texas Medical Branch, Galveston.

D. Paddon-Jones is an associate professor, Departments of Physical Therapy and Internal Medicine, The University of Texas Medical Branch, Galveston.

R. R. Wolfe is a professor, University of Arkansas for Medical Sciences, Little Rock; at the time of the study he was a professor, Department of Surgery, The University of Texas Medical Branch, Galveston.

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ResearchResearch and Professional BriefA Moderate Serving of High-Quality Protein Maximally Stimulates Skeletal Muscle Protein Synthesis in Young and Elderly Subjects

Abstract

Section snippets

Subjects and Experimental Design

Results and Discussion

Am J Clin Nutr

Am J Clin Nutr

Exp Gerontol

Metabolism

Am J Clin Nutr

Am J Clin Nutr

Am J Clin Nutr

The recommended dietary allowance for protein may not be adequate for older people to maintain skeletal muscle

J Gerontol A Biol Sci Med Sci

Functional and metabolic consequences of sarcopenia

J Nutr

The healthcare costs of sarcopenia in the United States

J Am Geriatr Soc

Epidemiology of sarcopenia among the elderly in New Mexico

Am J Epidemiol

A cross-sectional study of muscle strength and mass in 45- to 78-yr-old men and women

J Appl Physiol

Protein, weight management, and satiety

Am J Clin Nutr

The significance of protein in food intake and body weight regulation

Curr Opin Clin Nutr Metab Care

High protein intake sustains weight maintenance after body weight loss in humans

Int J Obes Relat Metab Disord

Research
Research and Professional Brief
A Moderate Serving of High-Quality Protein Maximally Stimulates Skeletal Muscle Protein Synthesis in Young and Elderly Subjects