The importance of dietary protein for muscle health in inactive, hospitalized older adults

Serum creatinine as an indicator of lean body mass in vegetarians and omnivores

Growing numbers of Americans are adopting vegetarian or vegan diets. While risk for some chronic conditions may be lower when following these diets, concern remains over the ability to consume adequate amounts of various nutrients, notably, protein. Knowing that serum creatinine is a reliable marker of muscle mass, this study examined the relationships between serum creatinine, lean body mass (LBM), handgrip strength, and protein intake in healthy vegetarian (n = 55) and omnivorous (n = 27) adults. Significantly higher protein intakes (+31%), LBM (+7%), serum creatinine (+12%) and handgrip strength (+14%) were observed for the omnivore participants compared to vegetarian participants. Positive correlations (p < 0.001) were noted between creatinine and LBM (R² = 0.42), creatinine and handgrip strength (R² = 0.41), protein intake and LBM (R² = 0.29), and handgrip strength and LBM (R² = 0.69). These data show that serum creatinine concentrations were lower in vegetarian women and men in comparison to their omnivorous counterparts and that serum creatinine concentrations correlate with LBM and strength in healthy adults, regardless of diet.

The efficacy of essential amino acid supplementation for augmenting dietary protein intake in older adults: implications for skeletal muscle mass, strength and function

The primary aim of this review is to evaluate the efficacy of essential amino acid (EAA) supplementation as a strategy to increase dietary protein intake and improve muscle mass, strength and function in older adults. A sufficient daily protein intake is widely recognised to be fundamental for the successful management of sarcopenia in older undernourished adults. In practice, optimising protein intakes in older adults is complex, requiring consideration of the dose and amino acid composition (i.e. a complete EAA profile and abundant leucine content) of ingested protein on a per meal basis, alongside the age-related decline in appetite and the satiating properties of protein. Recent studies in older adults demonstrate that EAA-based supplements are non-satiating and can be administered alongside food to enhance the anabolic properties of a meal containing a suboptimal dose of protein; an effect magnified when combined with resistance exercise training. These findings support the notion that EAA supplementation could serve as an effective strategy to improve musculoskeletal health in older adults suffering from non-communicable diseases such as sarcopenia. Compliance is critical for the long-term success of complex interventions. Hence, aspects of palatability and desire to eat are important considerations regarding EAA supplementation. In conclusion, EAA-based supplements enriched with l-leucine offer an alternative strategy to whole protein sources to assist older adults in meeting protein recommendations. In practice, EAA supplements could be administered alongside meals of suboptimal protein content, or alternatively between meals on occasions when older adults achieve their per meal protein intake recommendations.

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

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

Αcute effects of essential amino acid gel-based and whey protein supplements on appetite and energy intake in older women

Deficiencies in protein and energy intakes are partly responsible for age-related sarcopenia. We investigated the effects of supplements matched in essential amino acid (EAA) content (7.5 g) on energy intake and appetite. Ten women aged 69.2 ± 2.7 years completed 3 trials in a randomised, crossover design. Composite appetite scores, peptide-YY (PYY), and insulin responses to a 200-mL whey protein (WP) isolate (275 kJ), a 50-mL EAA gel (GEL, 478 kJ), or nothing as the control (CON) condition were investigated over 1 h, followed by an ad libitum breakfast. Energy intake at breakfast (CON, 1957 ± 713; WP, 1413 ± 623; GEL, 1963 ± 611 kJ) was higher in CON and GEL than in WP (both P = 0.006). After accounting for supplement energy content, energy intake in GEL was higher than in CON (P = 0.0006) and WP (P = 0.0008). Time-averaged area under the curve for composite appetite scores (CON, 74 ± 20; WP, 50 ± 22; GEL, 60 ± 16 mm) was higher in CON than WP (P = 0.015). Time-averaged area under the curve for PYY (CON, 87 ± 13; WP, 119 ± 27; GEL, 97 ± 22 pg·mL−1) was higher in WP than CON (P = 0.009) and GEL (P = 0.012). In conclusion, supplementation with WP facilitated an increase in protein intake, whereas supplementation with GEL increases in both energy and protein intakes, when consumed before an ad libitum breakfast. Such findings highlight potential gel-based EAA supplementation intake for addressing age-related sarcopenia.

Mung Bean Protein Supplement Improves Muscular Strength in Healthy, Underactive Vegetarian Adults

Although vegetarian diets are considered generally protective against chronic disease, nutrient deficiencies, including protein, are possible due to low bioavailability from plant-based sources. The consequences of inadequate dietary protein include reduced lean body mass (LBM) and muscle weakness. This study examined relationships between protein intake, strength, and LBM in 37 underactive vegetarians and recorded the impact of protein supplementation (18 g/day mung bean protein) on these indices utilizing an eight-week, randomized, controlled, feeding trial. Both handgrip and knee flexor and extensor strength were measured at baseline and week eight. At baseline, LBM was significantly related to grams of protein consumed daily. LBM was also correlated to grip strength (r = 0.569, p < 0.001) and lower body strength (r = 0.763 to 0.784; p < 0.001). Twenty-five vegetarians completed the feeding trial, including 11 in the protein supplementation group (PRO) and 14 in the control group (CON). At the end of the trial, LBM and strength did not differ significantly between groups. However, the average percent change for grip, flexor, and extensor strength did differ between PRO and CON participants (+2.9 ± 7.2% and −2.6 ± 7.3% respectively, p = 0.05). Thus, there were strong associations between dietary protein, LBM, and strength in vegetarians and an indication that supplementary vegetarian protein increased strength in the absence of exercise and independent of LBM.

The Effect of a Low Glycemic Index Pulse-Based Diet on Insulin Sensitivity, Insulin Resistance, Bone Resorption and Cardiovascular Risk Factors during Bed Rest

We determined the effects of a low glycemic-index pulse-based diet (i.e., containing lentils, chick peas, beans, and split peas) compared to a typical hospital diet on insulin sensitivity assessed by the Matsuda index from the insulin and glucose response to a two-hour oral glucose tolerance test, insulin resistance assessed by the homeostatic model assessment of insulin resistance (HOMA-IR), bone resorption assessed by 24 h excretion of urinary n-telopeptides(Ntx) and cardiovascular risk factors (blood lipids, blood pressure, arterial stiffness and heart rate variability) during bed rest. Using a randomized, counter-balanced cross-over design with one-month washout, six healthy individuals (30 ± 12 years) consumed the diets during four days of bed rest. The Matsuda index, HOMA-IR, urinary Ntx and cardiovascular risk factors were determined at baseline and after the last day of bed rest. Compared to the typical hospital diet, the pulse-based diet improved the Matsuda index (indicating increased insulin sensitivity; baseline to post-bed rest: 6.54 ± 1.94 to 6.39 ± 2.71 hospital diet vs. 7.14 ± 2.36 to 8.75 ± 3.13 pulse-based diet; p = 0.017), decreased HOMA-IR (1.38 ± 0.54 to 1.37 ± 0.50 hospital diet vs. 1.48 ± 0.54 to 0.88 ± 0.37 pulse-based diet; p = 0.022), and attenuated the increase in Ntx (+89 ± 75% hospital diet vs. +33 ± 20% pulse-based diet; p = 0.035). No differences for changes in cardiovascular risk factors were found between the two diet conditions, with the exception of decreased diastolic blood pressure during day three of bed rest in the pulse-based versus hospital diet (61 ± 9 vs. 66 ± 7 mmHg; p = 0.03). A pulse-based diet was superior to a hospital diet for maintaining insulin sensitivity, preventing insulin resistance, attenuating bone resorption and decreasing diastolic blood pressure during four days of bed rest.

Protein Requirements in Critically Ill Older Adults

Critically ill elderly patients' nutritional needs are not well understood and vary with the phase of illness and recovery. Patients' nutritional needs should be assessed early in hospitalization and re-assessed throughout the stay with additional attention during the transitions from critical illness, to severe illness, to post-hospital rehabilitation. In this review, we summarize recent findings and highlight recommendations for protein supplementation in critically ill geriatric patients throughout the stages of recovery. Future research specifically focusing on protein dose, its relationship with caloric needs, and delivery modality must be conducted to provide more specific guidelines for clinical practice.

Within-day protein distribution does not influence body composition responses during weight loss in resistance-training adults who are overweight

Background: Emerging research suggests that redistributing total protein intake from 1 high-protein meal/d to multiple moderately high-protein meals improves 24-h muscle protein synthesis. Over time, this may promote positive changes in body composition.Objective: We sought to assess the effects of within-day protein intake distribution on changes in body composition during dietary energy restriction and resistance training.Design: In a randomized parallel-design study, 41 men and women [mean ± SEM age: 35 ± 2 y; body mass index (in kg/m2): 31.5 ± 0.5] consumed an energy-restricted diet (750 kcal/d below the requirement) for 16 wk while performing resistance training 3 d/wk. Subjects consumed 90 g protein/d (1.0 ± 0.03 g · kg-1 · d-1, 125% of the Recommended Dietary Allowance, at intervention week 1) in either a skewed (10 g at breakfast, 20 g at lunch, and 60 g at dinner; n = 20) or even (30 g each at breakfast, lunch, and dinner; n = 21) distribution pattern. Body composition was measured pre- and postintervention.Results: Over time, whole-body mass (least-squares mean ± SE: -7.9 ± 0.6 kg), whole-body lean mass (-1.0 ± 0.2 kg), whole-body fat mass (-6.9 ± 0.5 kg), appendicular lean mass (-0.7 ± 0.1 kg), and appendicular fat mass (-2.6 ± 0.2 kg) each decreased. The midthigh muscle area (0 ± 1 cm2) did not change over time, whereas the midcalf muscle area decreased (-3 ± 1 cm2). Within-day protein distribution did not differentially affect these body-composition responses.Conclusion: The effectiveness of dietary energy restriction combined with resistance training to improve body composition is not influenced by the within-day distribution of protein when adequate total protein is consumed. This trial was registered at clinicaltrials.gov as NCT02066948.

Dietary Protein Intake Is Protective Against Loss of Grip Strength Among Older Adults in the Framingham Offspring Cohort

BACKGROUND

Age-related decline in muscle strength is an important public health issue for older adults. Dietary protein has been associated with maintenance of muscle mass, yet its relation to muscle strength remains unclear.

METHODS

We determined the association of dietary protein (total, animal, and plant) intake, measured by food frequency questionnaire, with change in grip strength over 6 years in 1,746 men and women from the Framingham Offspring cohort.

RESULTS

Mean age at baseline was 58.7 years (range: 29-85), and mean total, animal, and plant protein intakes were 79, 57, and 22 g/d, respectively. Adjusted baseline mean grip strength did not differ across quartiles of energy-adjusted total, animal or protein intake. Greater protein intake, regardless of source, was associated with less decrease in grip strength (all p for trend ≤.05): participants in the lowest quartiles lost 0.17% to 0.27% per year while those in the highest quartiles gained 0.52% to 0.60% per year. In analyses stratified by age, participants aged 60 years or older (n = 646) had similar linear trends on loss of grip strength for total and animal (all p for trend <.03) but not plant protein, while the trends in participants younger than 60 years (n = 896) were not statistically significant.

CONCLUSIONS

Higher dietary intakes of total and animal protein were protective against loss of grip strength in community-dwelling adults aged 60 years and older. Increasing intake of protein from these sources may help maintain muscle strength and support prevention of mobility impairment in older adults.

Optimizing Protein in the Older Adult

Aging is associated with specific physiological changes. One change that influences the functionality of an individual is the decrease in skeletal muscle. Research efforts to maintain skeletal muscle through dietary modifications have primarily focused on protein intake, including composition, quantity, and timing. Evidence demonstrates that adequacy, quality, and balance of protein intake are important; however, it should not replace the other dietary needs of the individual. The purpose of this article is to summarize the vast area of research regarding protein consumption in the aging population and place it in context of other nutritional concerns that affect this demographic. Efforts to educate older adults without providing overcomplicated guidelines will reduce the likelihood of individuals feeling overwhelmed, increasing dietary adherence.

Protein intake and muscle function in older adults

PURPOSE OF REVIEW

We provide an update on the recent advances in nutrition research regarding the role of protein intake in the development and treatment of sarcopenia of aging.

RECENT FINDINGS

Specific muscle mass, strength and function cut-points for the diagnosis of sarcopenia have been identified. There is mounting evidence, as highlighted by multiple consensus statements, that the Recommended Dietary Allowance (0.8 g/kg body weight) may be inadequate to promote optimal health in older adults. Recent research indicates that in addition to total daily protein intake the timing of protein intake is also important to best stimulate muscle protein synthesis, and maintain muscle mass and function in older adults.

SUMMARY

Recent evidence suggests that the Recommended Dietary Allowance for protein is inadequate, and that the timing and distribution of protein consumption throughout daily meals may be as important as the total quantity. Research has continued to advance our understanding of protein's effects on muscle metabolism; however, there remains a need for large, long-term, randomized clinical trials examining whether the positive effects of dietary protein on muscle metabolism seen in acute studies will translate over the long term into gains of muscle mass, function, and the overall health of older adults.