The Effect of a Whey Protein Supplement on Bone Mass in Older Caucasian Adults

Investigating the Health Implications of Whey Protein Consumption: A Narrative Review of Risks, Adverse Effects, and Associated Health Issues

This narrative review critically examines the current research on the health implications of whey protein (WP) supplementation, with a focus on potential risks and adverse effects. WP, commonly consumed for muscle building and weight loss, has been associated with various health concerns. Our comprehensive analysis involved a thorough search of multiple databases, resulting in the inclusion of 21 preclinical and human studies that collectively offer a detailed overview of WP's health impacts. The review reveals significant findings, such as WP's potential link to liver and kidney damage, alterations in gut microbiota, increased acne incidence, impacts on bone mass, and emotional and behavioural changes. These findings underscore the complexity of WP's effects on human health, indicating both beneficial and detrimental outcomes in relation to different posologies in a variety of settings. Our study suggests caution for the protein intake in situations of hepatic and renal compromised functions, as well as in acne susceptibility, while possible beneficial effects can be achieved for the intestinal microbiota, humoral and behavioural level, and finally bone and muscle mass in elderly. We emphasizes the importance of balanced WP consumption and call for more in-depth research to understand its long-term health effects. Health professionals and individuals considering WP supplementation should be aware of these potential risks and approach its use with informed caution.

The skeletal safety of milk-derived proteins: A meta-analysis of randomized controlled trials

PURPOSE

There has been a persistent claim that dairy products contain calcium-leaching proteins, although the soundness of such a claim has been challenged. A meta-analysis of randomized controlled trials (RCTs) on the effects of milk-derived protein supplementation on bone health indices in adults was performed to reconcile the controversy surrounding the potential skeletal safety concerns of proteins of dairy origin.

METHODS

The PubMed and Web of Science databases were searched for relevant RCTs. A random-effects model was used to generate pooled effect sizes and 95% confidence intervals.

RESULTS

Milk-derived protein supplementation did not significantly affect whole-body BMD (n = 7 RCTs) and BMD at the lumbar spine (n = 10), hip (n = 8), femoral neck (n = 9), trochanter (n = 5), intertrochanter (n = 2), and ultradistal radius (n = 2). The concentrations of bone formation markers (bone-specific alkaline phosphatase [n = 11], osteocalcin [n = 6], procollagen type 1 amino-terminal propeptide [n = 5]), bone resorption markers (N-terminal telopeptide of type 1 collagen [n = 7], C-terminal telopeptide of type 1 collagen [n = 7], deoxypyridinoline [n = 4]), and parathyroid hormone (n = 7) were not significantly affected. However, increased insulin-like growth factor-1 (IGF-1) concentrations (n = 13) were observed. Reduced IGF-1 concentrations were observed when soy protein was used as a comparator, and increased IGF-1 concentrations were observed when carbohydrate was used.

CONCLUSION

Our findings do not support the claim that proteins of dairy origin are detrimental to bone health.

Impact of Dietary Protein on Osteoporosis Development

Osteoporosis is a frequent yet unsolved health problem among older people. The influence of dietary protein still raises many questions regarding its quality and quantity in the context of bone health. The aim of this manuscript is to review the latest evidence on plant and animal protein influences on bone health in various groups of patients. The review is based on original studies, meta-analyses, randomized controlled trials, and prospective cohort studies published in PubMed and Cochrane databases during the last five years. Combining plant and animal protein with physical activity has the best effect on bones (muscle strengthening and reducing the risk of falls), while high protein intake can have adverse effects during bed rest. Despite the content of isoflavones, plant protein is not more beneficial than animal protein (dairy products) and can increase bone resorption markers. Hypoestrogenism due to menopause or eating disorders leads to low bone density and an increased risk of osteoporosis. A well-balanced diet with sufficient energy supply and protein intake (both of plant and animal origins) and adequate physical activity are crucial to ensure bone health. Dietary interventions should consider the quantity and quality of protein in patients with other comorbidities, particularly in an aging society.

Plasma Levels of Branched Chain Amino Acids, Incident Hip Fractures, and Bone Mineral Density of the Hip and Spine

OBJECTIVE

Branched chain amino acids (BCAA) are building blocks for protein, an essential component of bone. However, the association of plasma levels of BCAA with fractures in populations outside of Hong Kong or with hip fractures in particular is not known. The purpose of these analyses was to determine the relationship of BCAA including valine, leucine, and isoleucine and total BCAA (SD of the sum of Z-scores for each BCAA) with incident hip fractures and bone mineral density (BMD) of the hip and lumbar spine in older African American and Caucasian men and women in the Cardiovascular Health Study.

DESIGN

Longitudinal analyses of association of plasma levels of BCAA with incident hip fractures and cross-sectional BMD of the hip and lumbar spine from the Cardiovascular Health Study.

SETTING

Community.

PARTICIPANTS

A total of 1850 men (38% of cohort) and women; mean age 73 years.

MAIN OUTCOME MEASURES

Incident hip fractures and cross-sectional BMD of the total hip, femoral neck, and lumbar spine.

RESULTS

In fully adjusted models, over 12 years of follow-up, we observed no significant association between incident hip fracture and plasma values of valine, leucine, isoleucine, or total BCAA per 1 SD higher of each BCAA. Plasma values of leucine but not valine, isoleucine, or total BCAA, were positively and significantly associated with BMD of the total hip (P = .03) and femoral neck (P = .02), but not the lumbar spine (P = .07).

CONCLUSIONS

Plasma levels of the BCAA leucine may be associated with higher BMD in older men and women. However, given the lack of significant association with hip fracture risk, further information is needed to determine whether BCAAs would be novel targets for osteoporosis therapies.

The Influences of Macronutrients on Bone Mineral Density, Bone Turnover Markers, and Fracture Risk in Elderly People: A Review of Human Studies

Osteoporosis is a health condition that involves weak bone mass and a deteriorated microstructure, which consequently lead to an increased risk of bone fractures with age. In elderly people, a fracture attributable to osteoporosis elevates mortality. The objective of this review was to examine the effects of macronutrients on bone mineral density (BMD), bone turnover markers (BTMs), and bone fracture in elderly people based on human studies. A systematic search was conducted in the PubMed®/MEDLINE® database. We included human studies published up to April 2023 that investigated the association between macronutrient intake and bone health outcomes. A total of 11 meta-analyses and 127 individual human studies were included after screening the records. Carbohydrate consumption seemed to have neutral effects on bone fracture in limited studies, but human studies on carbohydrates' effects on BMD or/and BTMs are needed. The human studies analyzed herein did not clearly show whether the intake of animal, vegetable, soy, or milk basic proteins has beneficial effects on bone health due to inconsistent results. Moreover, several individual human studies indicated an association between eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and osteocalcin. Further studies are required to draw a clear association between macronutrients and bone health in elderly people.

Dietary Acid Load and Bone Health: A Systematic Review and Meta-Analysis of Observational Studies

Findings on the association between dietary acid load (DAL) and bone health are conflicting. This study aimed to summarize available studies on the association between DAL and risk of fractures or bone mineral density (BMD) in adults. Online databases including PubMed, Scopus, and Embase were searched for relevant studies published up to June 2021, using pertinent keywords. We identified observational studies (cohort, case-control, and cross-sectional) investigating the association between DAL and risk of fractures or BMD, then selected studies following these reported criteria: RRs with corresponding 95% CIs for the relationship between DAL and fracture risk; correlation coefficients for the association between DAL and BMD; and mean ± SD of BMD values across the categories of DAL. Overall, 17 studies with 80545 individuals were included. There was no significant relationship between the PRAL and fracture risk (Pooled RR: 1.18; 95% confidence interval 0.98 to 1.41, I² = 60.6%). Moreover, a similar association was observed between the NEAP and fracture risk (Pooled RR: 1.41, 95% CI: 0.79 to 2.52, I² = 54.1%). The results of five studies from four publications revealed no significant association between dietary PRAL score and femoral and spinal BMD (WMD femoral = −0.01, 95% confidence interval: −0.02 to 0.01, I² = 76.5%; WMD spinal = −0.01, 95% CI: −0.03 to 0.01, I² = 56.7%). However, being in the highest category of NEAP was significantly associated with a lower femoral and spinal BMD (WMD femoral = −0.01, 95% CI: −0.02 to −0.00, I² = 82.1%; WMD spinal = −0.02, 95% CI: −0.03 to −0.01, I² = 93%). It was showed that adopting diets high in acidity was not associated with risk of fractures. We also found a significant negative relationship between NEAP and BMD. However, DAL based on PRAL was not associated with BMD.

Calcium Homeostasis and Bone Metabolism in Goats Fed a Low Protein Diet

The objective of this study was to investigate the effects of low-protein diets on blood calcium (Ca) level, bone metabolism, and the correlation between bone metabolism and blood calcium in goats. Twenty-four female Xiangdong black goats with similar body weight (19.55 ± 3.55 kg) and age (8.0 ± 0.3 months) were selected and allocated into two groups: control group (CON, 10.77% protein content) and low-protein group (LP, 5.52% protein content). Blood samples were collected on days 1, 4, 7, 16 and 36 before morning feeding to determine the concentration of calcium (Ca), parathyroid hormone (PTH), bone gla protein (BGP), C-terminal telopeptide of type 1 collagen (CTX-1), bone alkaline phosphatase (BALP), and 1, 25-dihydroxyvitamin D3 [1,25(OH)₂D3]. Liver samples were collected to determine the expression of bone metabolism-related genes. There was no difference observed between LP and CON in concentration of plasma Ca or any of bone metabolism markers (P > 0.05). In the liver, the mRNA expression of bone gamma carboxyglutamate protein (BGLAP), alkaline phosphatase (ALPL), and mothers against decapentaplegic homolog-1 (SMAD1) were increased (P < 0.05) in LP as compared with CON. The correlation analysis of Ca and bone metabolism markers showed no significant correlation between Ca and bone metabolism. These results suggest that the blood Ca concentration in mature goats may keep at a stable level through nitrogen cycling when the providing protein is not enough.

The Effects of 12-Weeks Whey Protein Supplements on Markers of Bone Turnover in Adults With Abdominal Obesity - A Post Hoc Analysis

BACKGROUND

While osteoporosis is characterized by skeletal fragility due to increased bone turnover and low bone mineral density (BMD), subjects with abdominal obesity and type-2 diabetes have increased risk of bone fractures despite low bone turnover and increased BMD. Diets with increased protein content are reported to increase bone turnover in healthy adults and may be a point of interest in preserving bone strength in subjects with abdominal obesity and/or type-2 diabetes.

METHODS

We examined the effect of 12-weeks dietary intervention on bone turnover in 64 adults with abdominal obesity using data from the MERITS trial. The trial was a randomized, controlled, double blinded study in which participants were allocated to receive either 60 g/d of whey protein hydrolysate or maltodextrin in combination with either high (30 g/d) or low dietary fiber intake (10 g/d). Primarily, we assessed changes in plasma markers of bone turnover Procollagen type 1 N-terminal propeptide (p1NP), C-terminal telopeptide type-1 collagen (CTX), and parathyroid hormone (PTH) within the four intervention groups. In addition, we measured u-calcium and u-carbamide excretion, 25(OH)D, and BMD by whole body DXA scans. Finally, we compared changes in insulin resistance (Homeostasis-model assessment of insulin resistance, HOMA-IR) with changes in bone turnover markers.The trial was registered at www.clinicaltrials.gov as NCT02931630.

RESULTS

Sixty-four subjects were included in the study. We did not find any effect of twelve weeks of high protein or high fiber intake on plasma levels of P1NP or CTX. There was a nonsignificant positive association between protein intake and PTH levels (p=0.06). U-calcium and u-carbamide increased in both protein groups. There was a positive association between change in HOMA-IR and PTH (p=0.042), while changes in P1NP and CTX did not associate to changes in HOMA-IR.

CONCLUSION

Twelve weeks of increased whey protein intake in subjects with abdominal obesity did not affect markers of bone turnover significantly, although tended to increase PTH levels. Dietary fiber intake did not affect bone turnover. We report a positive association between change in HOMA-IR and PTH supporting a hypothesis of insulin resistance as a potential key factor in the expanding field of bone fragility in T2D subjects.

A review of recent evidence of dietary protein intake and health

The Korea National Health and Nutrition Examination Survey of 2013 to 2017 reported that the average protein consumption of the Korean population is above the current recommended nutrient intake of protein proposed by the Dietary Reference Intakes for Koreans. Some health professionals and the media often advise consuming diets high in protein for promoting metabolic regulation, weight control, and muscle synthesis. However, due to lack of scientific evidence, the validity and safety of high protein consumption are yet to be fully ascertained. The present review assesses recent evidence published in 2014–2020 from human studies, focusing on adequate protein intake and protein sources for the prevention of chronic diseases, particularly metabolic disorders and sarcopenia.

Nutrition, Physical Activity, and Dietary Supplementation to Prevent Bone Mineral Density Loss: A Food Pyramid

Bone is a nutritionally modulated tissue. Given this background, aim of this review is to evaluate the latest data regarding ideal dietary approach in order to reduce bone mineral density loss and to construct a food pyramid that allows osteopenia/osteoporosis patients to easily figure out what to eat. The pyramid shows that carbohydrates should be consumed every day (3 portions of whole grains), together with fruits and vegetables (5 portions; orange-colored fruits and vegetables and green leafy vegetables are to be preferred), light yogurt (125 mL), skim milk (200 mL,) extra virgin olive oil (almost 20 mg/day), and calcium water (almost 1 l/day); weekly portions should include fish (4 portions), white meat (3 portions), legumes (2 portions), eggs (2 portions), cheeses (2 portions), and red or processed meats (once/week). At the top of the pyramid, there are two pennants: one green means that osteopenia/osteoporosis subjects need some personalized supplementation (if daily requirements cannot be satisfied through diet, calcium, vitamin D, boron, omega 3, and isoflavones supplementation could be an effective strategy with a great benefit/cost ratio), and one red means that there are some foods that are banned (salt, sugar, inorganic phosphate additives). Finally, three to four times per week of 30-40 min of aerobic and resistance exercises must be performed.

Health Effects of Increasing Protein Intake Above the Current Population Reference Intake in Older Adults: A Systematic Review of the Health Council of the Netherlands

Whether older adults need more protein than younger adults is debated. The population reference intake for adults set by the European Food Safety Authority is 0.83 g/kg body weight (BW)/d based primarily on nitrogen balance studies, but the underlying data on health outcomes are outdated. An expert committee of the Health Council of the Netherlands conducted a systematic review (SR) of randomized controlled trials (RCTs) examining the effect of increased protein intake on health outcomes in older adults from the general population with an average habitual protein intake ≥0.8 g/(kg BW · d). Exposures were the following: 1) extra protein compared with no protein and 2) extra protein and physical exercise compared with physical exercise. Outcomes included lean body mass, muscle strength, physical performance, bone health, blood pressure, serum glucose and insulin, serum lipids, kidney function, and cognition. Data of >1300 subjects from 18 RCTs were used. Risk of bias was judged as high (n = 9) or "some concerns" (n = 9). In 7 of 18 RCTs, increased protein intake beneficially affected ≥1 of the tested outcome measures of lean body mass. For muscle strength, this applied to 3 of 8 RCTs in the context of physical exercise and in 1 of 7 RCTs without physical exercise. For the other outcomes, <30% (0-29%) of RCTs showed a statistically significant effect. The committee concluded that increased protein intake has a possible beneficial effect on lean body mass and, when combined with physical exercise, muscle strength; likely no effect on muscle strength when not combined with physical exercise, or on physical performance and bone health; an ambiguous effect on serum lipids; and that too few RCTs were available to allow for conclusions on the other outcomes. This SR provides insufficiently convincing data that increasing protein in older adults with a protein intake ≥0.8 g/(kg BW · d) elicits health benefits.

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

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

The Role of Diet in Bone and Mineral Metabolism and Secondary Hyperparathyroidism

Bone disorders are a common complication of chronic kidney disease (CKD), obesity and gut malabsorption. Secondary hyperparathyroidism (SHPT) is defined as an appropriate increase in parathyroid hormone (PTH) secretion, driven by either reduced serum calcium or increased phosphate concentrations, due to an underlying condition. The available evidence on the effects of dietary advice on secondary hyperparathyroidism confirms the benefit of a diet characterized by decreased phosphate intake, avoiding low calcium and vitamin D consumption (recommended intakes 1000-1200 mg/day and 400-800 UI/day, respectively). In addition, low protein intake in CKD patients is associated with a better control of SHPT risk factors, although its strength in avoiding hyperphosphatemia and the resulting outcomes are debated, mostly for dialyzed patients. Ultimately, a consensus on the effect of dietary acid loads in the prevention of SHPT is still lacking. In conclusion, a reasonable approach for reducing the risk for secondary hyperparathyroidism is to individualize dietary manipulation based on existing risk factors and concomitant medical conditions. More studies are needed to evaluate long-term outcomes of a balanced diet on the management and prevention of secondary hyperparathyroidism in at-risk patients at.

Effects of a whey protein pre-meal on bone turnover in participants with and without type 2 diabetes-A post hoc analysis of a randomised, controlled, crossover trial

AIMS

Whey protein may improve bone turnover and have anti-osteoporotic effects. The aim of the present randomised, controlled, crossover trial was to evaluate the effects of a whey protein pre-meal on bone turnover in people with type 2 diabetes and controls.

METHODS

Two groups, matched on sex, age and body mass index, comprising 12 participants with and 12 participants without type 2 diabetes were randomly given a pre-meal of whey protein (20 g) or water, which was consumed 15 min before a fat-rich meal or a fat-rich meal supplemented with 20 g whey protein. During a 360-min period, postprandial responses in bone turnover were examined.

RESULTS

Osteocalcin, P-procollagen type 1 amino terminal propeptide (P1NP), C-terminal cross-linked telopeptide of type-I collagen (CTX) and parathyroid hormone (PTH) were lower at baseline and PTH, osteocalcin and P1NP were lower during the entire postprandial phase in participants with type 2 diabetes than in participants without type 2 diabetes. We observed similar postprandial responses in bone turnover markers between persons with and without type 2 diabetes. We observed no effect of the whey protein or the water pre-meal on bone turnover markers. The changes were unrelated to secretion of hormones of the gut-bone axis.

CONCLUSION

Osteocalcin, P1NP, CTX and PTH all decreased following meal ingestion. We observed no convincing effect of a whey protein pre-meal on bone turnover. However, these results confirm that people with type 2 diabetes have low bone turnover and that the decreased bone formation markers are also extend into the postprandial responses.

Factors influencing the efficacy of nutritional interventions on muscle mass in older adults: a systematic review and meta-analysis

Context

Nutritional interventions stimulate muscle protein synthesis in older adults. To optimize muscle mass preservation and gains, several factors, including type, dose, frequency, timing, duration, and adherence have to be considered.

Objective

This systematic review and meta-analysis aimed to summarize these factors influencing the efficacy of nutritional interventions on muscle mass in older adults.

Data Sources

A systematic search was performed using the electronic databases MEDLINE, Embase, CINAHL, Cochrane Central Register of Controlled Trials, and SPORTDiscus from inception date to November 22, 2017, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Inclusion criteria included randomized controlled trials, mean or median age ≥65 years, and reporting muscle mass at baseline and postintervention. Exclusion criteria included genetically inherited diseases, anabolic drugs or hormone therapies, neuromuscular electrical stimulation, chronic kidney disease, kidney failure, neuromuscular disorders, and cancer.

Data Extraction

Extracted data included study characteristics (ie, population, sample size, age, sex), muscle mass measurements (ie, method, measure, unit), effect of the intervention vs the control group, and nutritional intervention factors (ie, type, composition, dose, duration, frequency, timing, and adherence).

Data Analysis

Standardized mean differences and 95%CIs were calculated from baseline to postintervention. A meta-analysis was performed using a random-effects model and grouped by the type of intervention.

Conclusions

Twenty-nine studies were included, encompassing 2255 participants (mean age, 78.1 years; SD, 2.22). Amino acids, creatine, β-hydroxy-β-methylbutyrate, and protein with amino acids supplementation significantly improved muscle mass. No effect was found for protein supplementation alone, protein and other components, and polyunsaturated fatty acids. High interstudy variability was observed regarding the dose, duration, and frequency, coupled with inconsistency in reporting timing and adherence. Overall, several nutritional interventions could be effective to improve muscle mass measures in older adults. Because of the substantial variability of the intervention factors among studies, the optimum profile is yet to be established.

Systematic Review Registration

PROSPERO registration no. CRD42018111306.

Effect of Acid or Base Interventions on Bone Health: A Systematic Review, Meta-Analysis, and Meta-Regression

Osteoporosis is a global health issue among the aging population. The effect of the acid or base interventions on bone health remains controversial. This study performed a systematic review and meta-analysis to investigate effects of acidic diets and alkaline supplements on bone health simultaneously. We conducted a comprehensive literature search in 5 available databases and 1 registered clinical trial system to identify randomized controlled trials (RCTs) that assessed effects of the acid-base intervention on bone health. Depending on heterogeneity across studies, the pooled effects were calculated by fixed-effects or random-effects models. The present study included 13 acidic diet intervention studies and 13 alkaline supplement studies for final quantitative assessments. The meta-analysis showed that acidic diets significantly increased net acid excretion [NAE; standardized mean difference (SMD) = 2.99; P = 0.003] and urinary calcium excretion (SMD = 0.47, P < 0.00001) but had no significant effect on bone turnover markers and bone mineral density (BMD). On the other hand, alkaline supplement intervention significantly reduced NAE (SMD = -1.29, P < 0.00001), urinary calcium excretion (SMD = -0.44, P = 0.007), bone resorption marker aminoterminal cross-linking telopeptide (NTX; SMD = -0.29, P = 0.003), and bone formation marker osteocalcin (OC; SMD = -0.23, P = 0.02), but did not affect the other bone turnover markers. Furthermore, alkaline supplements significantly increased BMD in femoral neck [mean difference (MD) = 1.62, P < 0.00001, I2 = 0%], lumbar spine (MD = 1.66, P < 0.00001, I2 = 87%), and total hip (MD = 0.98, P = 0.02, I2 = 99%). Subsequently, meta-regression analyses identified 1 study that substantially contributed to the high heterogeneity of BMD in the latter 2 sites, but sensitivity analysis suggested that this study did not affect the significant pooled effects. Despite that, the results should be interpreted with caution and need to be further validated by a larger RCT. In summary, through integrating evidence from RCTs, the present meta-analysis initially suggests that alkaline supplements may be beneficial to bone metabolism and acidic diets may not be harmful to bone health. This work may be clinically useful for both clinicians and patients with osteoporosis.

Daily Supplementation With Whey, Soy, or Whey-Soy Blended Protein for 6 Months Maintained Lean Muscle Mass and Physical Performance in Older Adults With Low Lean Mass

BACKGROUND

Few studies have investigated the effect of long-term protein supplementation alone on muscle health in older adults with low lean mass.

OBJECTIVE

To determine the effect of whey, soy or whey-soy blended protein supplementation on lean muscle mass and physical performance in older adults with low lean mass.

DESIGN

A 4-arm randomized controlled trial.

PARTICIPANTS/SETTING

Chinese older adults (n = 123, 65-79 years) with low lean mass (appendicular skeletal muscle index < 7.0 kg/m² in men and < 5.4 kg/m² in women) living in the urban area of Guangzhou participated between October 2015 and June 2016.

INTERVENTION

Participants were randomly assigned to receive approximately 16 g/d of whey, soy, or whey-soy blend protein or maintained habitual diets in control group for 6 months.

MAIN OUTCOME MEASURES

Lean mass, handgrip strength, and physical performance (gait speed, chair stand test, and Short Physical Performance Battery) were assessed at baseline and 6 months.

STATISTICAL ANALYSES

Two-way analysis of variance with the main effects of treatment and time and treatment × time interaction and analysis of covariance was used to determine differences in outcomes.

RESULTS

Appendicular skeletal muscle index, lean mass, percent lean mass in legs and appendicular areas, gait speed, and Short Physical Performance Battery score were maintained in the treatment groups and decreased in the control group, resulting in significant reduction in these variables from baseline in the control compared with treatment groups (all P < .01; percent differences between treatment and control groups ranged from 80% to 156%). The chair stand test time at month 6 decreased from baseline in the treatment groups and increased in the control group, resulting in a significant increase in the control compared with treatment groups (all P < .01; percent differences between treatment and control groups ranged from 132% to 155%). Handgrip strength remained unchanged. There were no significant differences in outcomes among treatment groups.

CONCLUSIONS

Supplementation with whey, soy, or whey-soy blended protein for 6 months equally maintained lean muscle mass and physical performance in older adults with low lean mass.

Combined effect of citrulline and lactoserum on amino acid availability in aged rats

OBJECTIVE

Age-associated sarcopenia is due to anabolic resistance to feeding. Muscle protein synthesis is improved by fast proteins (e.g., lactoserum), which increase peripheral amino acid (AA) bioavailability more rapidly than slow proteins (e.g., casein), and by citrulline. Citrulline, which limits splanchnic sequestration of AA, may more effectively increase peripheral AA bioavailability when combined with lactoserum than with casein when administered as an oral nutritional protein supplement.

METHODS

In this study, 25 fasted aged rats received a single gavage administration of lactoserum or casein 0.4 g/kg, alone or with citrulline 0.4 g/kg, and AA pharmacokinetics, glucose, insulin, triglycerides, and insulin-like growth factor 1 (IGF1) were monitored for 4 h. At 4 h, muscle protein and AA contents and protein synthesis activation were measured.

RESULTS

While lactoserum was associated with higher AA availability, citrulline exerts only limited effects on the plasma profile of AAs from the two proteins. Maximum plasma citrulline was reached earlier with casein (T90 min) than with lactoserum (T120 min). A protein x citrulline interaction was observed for some plasma and muscle AA levels with a significant activation of mechanistic target of rapamycin complex 1 (mTORC1) signaling suggesting higher anabolism with the combination of citrulline and lactoserum. Lower plasma and muscle AA levels with citrulline and lactoserum compared to lactoserum alone suggest a greater AA utilization in a context of muscle anabolic signaling activation.

CONCLUSION

Provision of a citrulline-lactoserum combination as a nutritional supplement could therefore be beneficial in terms of muscle protein balance and prevention of sarcopenia. Further studies are warranted to evaluate the efficacy of this combination.

The Effects of Cow-Milk Protein Supplementation in Elderly Population: Systematic Review and Narrative Synthesis

Background. To review currently available evidence on the effect of cow-milk proteins supplementation (CPS) on health in the elderly. Methods. Five electronic databases (Pubmed, Web of Science, Embase, Cochrane Library, ClinicalTrials.gov) were searched for studies about CPS among older people. All types of publications were included, with the exception of systematic reviews, meta-analyses, opinion letters, editorials, case reports, conference abstracts and comments. An additional search in Google Scholar and a manual review of the reference lists were performed. Results. Overall, 103 studies were included. Several studies explored the role of CPS in the preservation or improvement of muscle mass among healthy subjects (40 studies) and pre-frail, frail or sarcopenic patients (14), with evidence of beneficial effects. Other studies assessed the effect of CPS on bones (12), cardiovascular disease (8), inflamm-aging (7), chronic pulmonary disease (4), neurocognitive function (4), and vaccines (2), with weak evidence of positive effects. Seven studies in the field of protein metabolism investigated the role of CPS as an important contributor to nutritional needs. Other investigational areas are considered in the last five studies. Conclusions. The beneficial effects of CPS in achieving aged-related nutritional goals, in preserving muscle mass and in recovering after hospitalization may be particularly relevant in the elderly.

Effects of low-dose milk protein supplementation following low-to-moderate intensity exercise training on muscle mass in healthy older adults: a randomized placebo-controlled trial

PURPOSE

The purpose of this study was to examine whether long-term ingestion of low-dose milk protein supplementation causes a greater increase in muscle mass and strength of older adults during low-to-moderate intensity exercise training intervention than isocaloric carbohydrate.

METHODS

In a randomized, double-blind, and placebo-controlled design, 122 healthy older adults (60-84 year) received either an acidified milk protein drink containing 10 g of milk protein (MILK; n = 61) or an isocaloric placebo drink (PLA; n = 61) daily throughout 6 months of body weight and medicine ball exercise training. Measurements before and after the intervention included body composition, physical performance and blood biochemistry.

RESULTS

Lean body mass significantly increased in the MILK group (+ 0.54 kg, p < 0.001), but did not change in the PLA group (- 0.10 kg, p = 0.534). The increases in the MILK group were significantly greater than in the PLA group (p = 0.004). Fat mass (- 0.77 kg) and plasma uric acid levels (- 0.3 mg/dL) significantly decreased only in the MILK group (p < 0.001), with a significant group difference (p = 0.002 and p < 0.001, respectively). Most of the physical performance tests significantly improved in both groups, but no group differences were found.

CONCLUSION

We conclude that low-dose milk protein supplementation (10 g of protein/day) combined with low-to-moderate intensity exercise training is associated with increased muscle mass, but not improved physical performance compared to carbohydrate combined with exercise in healthy older adults. This study was registered in the UMIN Clinical Trials Registry (UMIN000032189).

Amount of Protein Required to Improve Muscle Mass in Older Adults

Increased protein intake has been suggested as an effective strategy to treat age-related loss of muscle mass and function, but the amount of protein required to improve muscle and function without exercise in older adults remains unclear. Thus, this secondary data analysis aimed to assess what amount of protein from habitual protein intake was positively associated with changes in muscle mass and gait speed in older women and men. Ninety-six community-dwelling older adults consumed 0.8, 1.2, or 1.5 g/kg/day of protein and maintained their usual physical activity for 12 weeks. Increased protein intake of >0.54 g/kg/day was positively associated with changes in appendicular skeletal muscle mass (ASM)/weight (B = 0.591, p = 0.026), ASM/body mass index (B = 0.615, p = 0.023), and ASM:fat ratio (B = 0.509, p = 0.030) in older men. However, change in protein intake was not associated with change in muscle mass in older women. Additionally, change in protein intake was not associated with change in gait speed in older women and men. The present study suggested that an increased absolute protein amount of >0.54 g/kg/day from habitual protein intake was positively associated with change in muscle mass in older men.

Whey protein ingestion in elderly diet and the association with physical, performance and clinical outcomes

Nutrition is critical to the health of the elderly, since most of them have a deficiency in key nutrient. The use of whey protein may be a food strategy to increase protein intake. The objective of this work was to evaluate the ingestion of whey protein for the elderly and the association with physical performance and clinical outcomes. A systematic review was conducted in order to find papers that shed some light in the correlation between whey protein and the elderly.

INCLUSION CRITERIA

population: elderly; intervention: use of whey protein when compared to control group; outcome: related to health, nutrition, or quality of life.

DATABASE

PubMed, with papers published in the last 5 years.

SEARCH STRATEGY

(elder OR senior OR elderly OR aging OR aged OR old OR older) AND (whey OR "whey protein"). 35 papers were selected of which 22 had a physical performance outcome and 13 had clinical outcomes. Studies indicate that whey protein supplements promote protein synthesis in the elderly, improving muscle performance and aerobic capacity, protecting against sarcopenia and reducing the risk for falls. In the papers studied, the age group considered to be elderly was ≥65 years in 27 papers and ≥60 years in the other 8 papers. Whey protein also appears to contribute to improved health, recovery from disease, prevention of cardiovascular and metabolic risks, and hepatic steatosis complications. Data suggest that whey protein supplements may be promising for the health improvement of the elderly.

Effects of Whey Protein Supplementation on Aortic Stiffness, Cerebral Blood Flow, and Cognitive Function in Community-Dwelling Older Adults: Findings from the ANCHORS A-WHEY Clinical Trial

ANCHORS A-WHEY was a 12-week randomized controlled trial (RCT) designed to examine the effect of whey protein on large artery stiffness, cerebrovascular responses to cognitive activity and cognitive function in older adults. Methods: 99 older adults (mean ± SD; age 67 ± 6 years, BMI 27.2 ± 4.7kg/m², 45% female) were randomly assigned to 50g/daily of whey protein isolate (WPI) or an iso-caloric carbohydrate (CHO) control for 12 weeks (NCT01956994). Aortic stiffness was determined as carotid-femoral pulse wave velocity (cfPWV). Aortic hemodynamic load was assessed as the product of aortic systolic blood pressure and heart rate (Ao SBP × HR). Cerebrovascular response to cognitive activity was assessed as change in middle-cerebral artery (MCA) blood velocity pulsatility index (PI) during a cognitive perturbation (Stroop task). Cognitive function was assessed using a computerized neurocognitive battery. Results: cfPWV increased slightly in CHO and significantly decreased in WPI (p < 0.05). Ao SBP × HR was unaltered in CHO but decreased significantly in WPI (p < 0.05). Although emotion recognition selectively improved with WPI (p < 0.05), WPI had no effect on other domains of cognitive function or MCA PI response to cognitive activity (p > 0.05 for all). Conclusions: Compared to CHO, WPI supplementation results in favorable reductions in aortic stiffness and aortic hemodynamic load with limited effects on cognitive function and cerebrovascular function in community-dwelling older adults.

High-protein supplementation facilitates weight training-induced bone mineralization in baseball players

OBJECTIVES

The aim of this study was to determine whether weight training combined with high-protein intake enhances total and regional bone mineral density (BMD) in athletes.

METHODS

BMD of 27 Division 1 collegiate baseball players 18 to 22 y of age (N = 13, 2 dropouts) received either 14% protein or isocaloric 44% protein supplements and were assessed by dual-energy x-ray absorptiometry before and after a 12-wk weight training program (challenging upper and lower body).

RESULTS

Baseline data showed unequivocally greater humerus BMD in the dominant arm than their contralateral non-dominant arm (∼20 %) among all baseball players. Humerus BMD of the non-dominant arm was enhanced by 2.7% after weight training for both low- and high-protein groups (main effect, P = 0.008), concurrent with an unexpected small decrease in total body BMD (main effect, P = 0.014). Humerus BMD of the dominant arm with greater baseline value than the non-dominant arm was not increased unless high protein was supplemented (+2.7 %; P < 0.05).

CONCLUSION

Bones with relatively higher BMD show blunt adaptation against training, which can be relieved by high-protein supplementation. Total BMD of athletes cannot be further elevated by weight training.

Dietary protein intake and bone health

Considerable attention has recently focused on dietary protein's role in the mature skeleton. The aim was to conduct a systematic review evaluating the effects of dietary protein intake alone on bone health measures in adults (Bone Mineral Density (BMD) and bone biomarkers. Searches across 3 databases were conducted through February 2019 including randomized controlled trials (RCT's) and prospective cohort studies examining the effects of ''high versus low'' protein intake. Studies in various populations are currently limited, varying doses and dietary compositions were used or prescribed, respectively, and there was medium risk of bias among the RCTs and the cohort studies examined. Moderate evidence suggested that higher protein intake may have protective effect on lumbar spine (LS) bone mineral density (BMD) compared with lower protein intake but no effect on total hip (TH), femoral neck (FN), or total body BMD or bone biomarkers. Current evidence shows no adv erse effects of higher protein intakes. Although there were positive trends on BMD at most bone cites, only the LS showed moderate evidence to support benefits of higher protein intake. Studies were heterogeneous. High-quality, long-term studies are needed to clarify dietary protein's role in bone health.

Health Benefits of Whey or Colostrum Supplementation in Adults ≥35 Years; a Systematic Review

Food-health claims are an important method of translating nutrition research to consumers. Whey and colostrum are thought to exert health benefits to adults, but it is unclear what measurable, objective health benefits they impart. This review aimed to identify the objective health benefits of bovine whey or colostrum-based beverages to healthy adults aged ≥35 years to substantiate a food-health claim. Seven databases were systematically searched. Eligible articles were RCTs that involved healthy adults aged ≥35 years, consuming whey or colostrum in beverage form and measuring objective health markers. Quality assessment and data extraction was conducted in duplicate. The searches identified 9943 papers and 16 were included in this review; 13 studies, reported across 15 papers, related to whey, one study to colostrum. The outcomes identified were body composition, bone mineral density, biochemical markers, such as blood glucose and lipids, and muscle strength and synthesis. Heterogeneous outcomes, high risk of bias and inconsistent findings resulted in inconclusive evidence to substantiate a food-health claim. Clearer reporting and consensus on a minimum set of objective measures would allow for more robust recommendations regarding food-health claims. Protecting consumers from misleading health claims will require collaboration between regulators, researchers, and the food industry.

Marrow adipose tissue gradient is preserved through high protein diet and bed rest. A randomized crossover study

Context

Marrow adipose tissue (MAT) has a peripheral to central distribution in adults, higher in peripheral bones. Similarly, the spine has a caudal to cephalad MAT distribution, higher in lumbar vertebras. Diet and the level of physical activities are known modulators of MAT with significant impact on bone; however, whether these can modulate the MAT gradient is unknown.

Objective

To measure the effect of high protein diet and bed rest interventions on the lumbar MAT gradient.

Design participants intervention

In a prospective randomized crossover trial, 10 healthy men participated in 2 consecutive campaigns of 21days head-down-tilt-bed-rest (HDTBR). They received either whey protein and potassium bicarbonate-supplemented or control diet separated by a 4-month washout period.

Main outcome measures

Ten serial MRI measures of lumbar vertebral fat fraction (VFF) were performed at baseline, 10days and 20days of HDTBR and 3 and 28days after HDTBR of each bed rest campaign.

Results

The mean L5-L1 VFF difference of 4.2 ± 1.2 percentage point higher at L5 (p = 0.008) constituted a caudal to cephalad lumbar MAT gradient. High protein diet did not alter the lumbar VFF differences during both HDTBR campaigns (all time points p > 0.05). Similarly, 2 campaigns of 21days of HDTBR did not change the lumbar VFF differences (all time points p > 0.05).

Conclusions

This pilot study established that the lumbar vertebral MAT gradient was not altered by a high protein nor by 2 × 21days bed rest interventions. These findings demonstrated that this lack of mechanical stimulus was not an important modulator of the lumbar MAT gradient. The highly preserved MAT gradient needs to be measured in more situations of health and disease and may potentially serve to detect pathological situations.

The Association of Aromatic Amino Acids with Incident Hip Fracture, aBMD, and Body Composition from the Cardiovascular Health Study

In 5187 persons from the Cardiovascular Health Study, there was no significant association of dietary intakes of aromatic amino acids (AAA) with areal BMD of the hip or body composition. However, those who had the lowest dietary intakes of AAA were at increased risk for incident hip fractures. Prior studies of the association of protein intake with osteoporosis are conflicting and have not directly examined the relationship of aromatic amino acids (AAA) with fractures, areal bone mineral density (aBMD), and body composition. We sought to determine the relationship of dietary intakes of AAA with osteoporosis parameters in elderly men and women. 5187 men and women aged ≥ 65 years from the Cardiovascular Health Study (CHS) with dietary intakes of AAA (tryptophan, phenylalanine, tyrosine) estimated by food frequency questionnaire (FFQ) were included. We examined the relationship between a one-time estimate of daily dietary AAA intake with risk of incident hip fractures over a median of 13.2 years of fracture follow-up. A subset (n = 1336) who had dual energy X-ray absorptiometry (DXA) performed were included in a cross-sectional analysis of the association of dietary AAA intake with aBMD of the total hip and measurements of body composition. In multivariable models adjusted for demographic and clinical variables, medication use, and diet, higher dietary AAA intake was not significantly associated with incident hip fractures. All hazard ratios (HR) were less than one (tryptophan, HR 0.14, 95% CI 0.01 to 1.89; phenylalanine, HR 0.60, 95% CI 0.23 to 1.55; tyrosine, HR 0.59, 95% CI 0.27 to 1.32), but confidence intervals were wide and included no difference. However, in post hoc analyses, the lowest quartile of intake for each AAA was associated with an increased risk for hip fracture compared to higher quartiles (p ≤ 0.047 for all). Dietary AAA intakes were not significantly associated with total hip aBMD or any measurements of body composition. Overall, there was no significant association of dietary AAA intake with hip fractures, aBMD of the hip, or body composition. However, there may be a subset of elderly individuals with low dietary intakes of AAA who are at increased for hip fractures.

Whey protein in cancer therapy: A narrative review

Cancer remains a public health challenge in the identification and development of ideal pharmacological therapies and dietary strategies. The use of whey protein as a dietary strategy is widespread in the field of oncology. The two types of whey protein, sweet or acid, result from several processing techniques and possess distinct protein subfraction compositions. Mechanistically, whey protein subfractions have specific anti-cancer effects. Alpha-lactalbumin, human α-lactalbumin made lethal to tumor cell, bovine α-lactalbumin made lethal to tumor cell, bovine serum albumin, and lactoferrin are whey protein subfractions with potential to hinder tumor pathways. Such effects, however, are principally supported by studies performed in vitro and/or in vivo. In clinical practice, whey protein intake-induced anti-cancer effects are indiscernible. However, whey protein supplementation represents a practical, feasible, and cost-effective approach to mitigate cancer cachexia syndrome. The usefulness of whey protein is evidenced by a greater leucine content and the potential to modulate IGF-1 concentrations, representing important factors towards musculoskeletal hypertrophy. Further clinical trials are warranted and needed to establish the effects of whey protein supplementation as an adjuvant to cancer therapy.

Dietary protein and bone health across the life-course: an updated systematic review and meta-analysis over 40 years

We undertook a systematic review and meta-analysis of published papers assessing dietary protein and bone health. We found little benefit of increasing protein intake for bone health in healthy adults but no indication of any detrimental effect, at least within the protein intakes of the populations studied. This systematic review and meta-analysis analysed the relationship between dietary protein and bone health across the life-course. The PubMed database was searched for all relevant human studies from the 1st January 1976 to 22nd January 2016, including all bone outcomes except calcium metabolism. The searches identified 127 papers for inclusion, including 74 correlational studies, 23 fracture or osteoporosis risk studies and 30 supplementation trials. Protein intake accounted for 0-4% of areal BMC and areal BMD variance in adults and 0-14% of areal BMC variance in children and adolescents. However, when confounder adjusted (5 studies) adult lumbar spine and femoral neck BMD associations were not statistically significant. There was no association between protein intake and relative risk (RR) of osteoporotic fractures for total (RR_(random) = 0.94; 0.72 to 1.23, I² = 32%), animal (RR _(random) = 0.98; 0.76 to 1.27, I² = 46%) or vegetable protein (RR _(fixed) = 0.97 (0.89 to 1.09, I² = 15%). In total protein supplementation studies, pooled effect sizes were not statistically significant for LSBMD (total n = 255, MD_(fixed) = 0.04 g/cm² (0.00 to 0.08, P = 0.07), I² = 0%) or FNBMD (total n = 435, MD_(random) = 0.01 g/cm² (-0.03 to 0.05, P = 0.59), I² = 68%). There appears to be little benefit of increasing protein intake for bone health in healthy adults but there is also clearly no indication of any detrimental effect, at least within the protein intakes of the populations studied (around 0.8-1.3 g/Kg/day). More studies are urgently required on the association between protein intake and bone health in children and adolescents.

Dairy foods and bone health throughout the lifespan: a critical appraisal of the evidence

The consumption of high-Ca, high-protein dairy foods (i.e. milk, cheese, yogurt) is advocated for bone health across the lifespan to reduce the risk of low-trauma fractures. However, to date, the anti-fracture efficacy of dairy food consumption has not been demonstrated in randomised controlled trials but inferred from cross-sectional and prospective studies. The anti-fracture efficacy of dairy food consumption is plausible, but testing this requires a robust study design to ensure outcomes are suitably answering this important public health question. The evidence of skeletal benefits of dairy food consumption is equivocal, not because it may not be efficacious but because the study design and execution are often inadequate. The key issues are compliance with dietary intervention, dropouts, sample sizes and most importantly lack of deficiency before intervention. Without careful appraisal of the design and execution of available studies, precarious interpretations of outcomes may be made from these poorly designed or executed studies, without consideration of how study design may be improved. Dairy food interventions in children are further hampered by heterogeneity in growth: in particular sex and maturity-related differences in the magnitude, timing, location and surface-specific site of bone accrual. Outcomes of studies combining children of different sexes and maturity status may be masked or exaggerated by these differences in growth, so inaccurate conclusions are drawn from results. Until these critical issues in study design are considered in future dairy food interventions, the anti-fracture efficacy of dairy food consumption may remain unknown and continue to be based on conjecture.

The Effects of a High-Protein Diet on Bone Mineral Density in Exercise-Trained Women: A 1-Year Investigation

The effects of long-term high-protein consumption (i.e., >2.2 g/kg/day) are unclear as it relates to bone mineral content. Thus, the primary endpoint of this investigation was to determine if consuming a high-protein diet for one year affected various parameters of body composition in exercise-trained women. This investigation is a follow-up to a prior 6-month study. Subjects were instructed to consume a high-protein diet (>2.2 g/kg/day) for one year. Body composition was assessed via dual-energy X-ray absorptiometry (DXA). Subjects were instructed to keep a food diary (i.e., log their food ~three days per week for a year) via the mobile app MyFitnessPal^®. Furthermore, a subset of subjects had their blood analyzed (i.e., basic metabolic panel). Subjects consumed a high-protein diet for one year (mean ± SD: 2.3 ± 1.1 grams per kilogram body weight daily [g/kg/day]). There were no significant changes for any measure of body composition over the course of the year (i.e., body weight, fat mass, lean body mass, percent fat, whole body bone mineral content, whole body T-score, whole body bone mineral density, lumbar bone mineral content, lumbar bone mineral density and lumbar T-score). In addition, we found no adverse effects on kidney function. Based on this 1-year within-subjects investigation, it is evident that a diet high in protein has no adverse effects on bone mineral density or kidney function.

Effects of protein supplementation on lean body mass, muscle strength, and physical performance in nonfrail community-dwelling older adults: a systematic review and meta-analysis

Background

Increasing protein intake has been suggested as an effective strategy to ameliorate age-related loss of muscle mass and strength. Current reviews assessing the effect of protein supplementation are strongly influenced by the inclusion of studies with frail older adults.

Objectives

We assessed the effect of protein supplementation on lean body mass, muscle strength, and physical performance in exclusively nonfrail community-dwelling older adults. Moreover, we assessed the superior effects of protein supplementation during concomitant resistance exercise training on muscle characteristics.

Design

A systematic literature search was conducted on PubMed, Embase, and Web of Science up to 15 May 2018. We included randomized controlled trials that assessed the effect of protein supplementation on lean body mass, muscle thigh cross-sectional area, muscle strength, gait speed, and chair-rise ability and performed random-effects meta-analyses.

Results

Data from 36 studies with 1682 participants showed no significant effects of protein supplementation on changes in lean body mass [standardized mean difference (SMD): 0.11; 95% CI: -0.06, 0.28], handgrip strength (SMD: 0.58; 95% CI: -0.08, 1.24), lower extremity muscle strength (SMD: 0.03; 95% CI: -0.20, 0.27), gait speed (SMD: 0.41; 95% CI: -0.04, 0.85), or chair-rise ability (SMD: 0.10; 95%: CI -0.08, 0.28) compared with a control condition in nonfrail community-dwelling older adults. Moreover, no superior effects of protein supplementation were found during concomitant resistance exercise training on muscle characteristics.

Conclusions

Protein supplementation in nonfrail community-dwelling older adults does not lead to increases in lean body mass, muscle cross-sectional area, muscle strength, or physical performance compared with control conditions; nor does it exert superior effects when added to resistance exercise training. Habitual protein intakes of most study participants were already sufficient, and protein interventions differed in terms of type of protein, amount, and timing. Future research should clarify what specific protein supplementation protocol is beneficial for nonfrail community-dwelling older adults with low habitual protein intake.

Protein supplementation improves muscle mass and physical performance in undernourished prefrail and frail elderly subjects: a randomized, double-blind, placebo-controlled trial

Background

Age-related loss of muscle mass and function is a major component of frailty. Nutrition supplementation with exercise is an effective strategy to decrease frailty by preventing sarcopenia, but the effect of protein alone is controversial.

Objective

The present study was performed to investigate a dose-dependent effect of protein supplementation on muscle mass and frailty in prefrail or frail malnourished elderly people.

Design

A 12-wk double-blind randomized controlled trial was conducted in elderly subjects aged 70-85 y with ≥1 of the Cardiovascular Health Study frailty criteria and a Mini Nutritional Assessment score ≤23.5 (n = 120). Participants were randomly assigned to 1 of 3 groups: 0.8, 1.2, or 1.5 g protein · kg-1 · d-1, with concealed allocation and intention-to-treat analysis. Primary outcomes were appendicular skeletal muscle mass (ASM) and skeletal muscle mass index (SMI) measured by dual-energy X-ray absorptiometry.

Results

After the 12-wk intervention, the 1.5-g protein · kg-1 · d-1 group had higher ASM (mean ± SD: 0.52 ± 0.64 compared with 0.08 ± 0.68 kg, P = 0.036) and SMI (ASM/weight: 0.87% ± 0.69% compared with 0.15% ± 0.89%, P = 0.039; ASM/BMI: 0.02 ± 0.03 compared with 0.00 ± 0.04, P = 0.033; ASM:fat ratio: 0.04 ± 0.11 compared with -0.02 ± 0.10, P = 0.025) than the 0.8-g protein · kg-1 · d-1 group. In addition, gait speed was improved in the 1.5-g protein · kg-1 · d-1 group compared with the 0.8-g protein · kg-1 · d-1 group (0.09 ± 0.07 compared with 0.04 ± 0.07 m/s, P = 0.039). There were no significant differences between the 1.2- and 0.8-g protein · kg-1 · d-1 groups in muscle mass and physical performance. No harmful adverse effects were observed.

Conclusions

The present study indicates that protein intake of 1.5 g · kg-1 · d-1 has the most beneficial effects in regard to preventing sarcopenia and frailty compared with protein intakes of 0.8 and 1.2 g · kg-1 · d-1 in prefrail or frail elderly subjects at risk of malnutrition. This trial was registered at cris.nih.go.kr as KCT0001923.

Amino acids as signaling molecules modulating bone turnover

Except for the essential amino acids (AAs), much of the focus on adequate dietary protein intake has been on total nitrogen and caloric intake rather than AA composition. Recent data, however, demonstrate that "amino-acid sensing" can occur through either intracellular or extracellular nutrient-sensing mechanisms. In particular, members of the class 3 G-protein coupled receptor family, like the calcium-sensing receptor are known to preferentially bind specific AAs, which then modulate receptor activation by calcium ions and thus potentially impact bone turnover. In pursuing the possibility of direct nutrient effects on bone cells, we examined individual AA effects on osteoprogenitor/bone marrow stromal cells (BMSCs), a key target for bone anabolism. We demonstrate that BMSCs express both intracellular and extracellular nutrient sensing pathways and that AAs are required for BMSC survival. In addition, certain AA types, like members of the aromatic AAs, can potently stimulate increases in intracellular calcium and ERK phosphorylation/activation. Further, based on the in vitro data, we examined the effect of specific AAs on bone mass. To better evaluate the impact of specific AAs, we added these to a low-protein diet. Our data demonstrate that a low-protein diet itself is associated with a significant drop in bone mineral density (BMD) in the older mice, related, at least in part, to an increase in osteoclastic activity. This drop in BMD in mice on the low-protein diet is prevented by addition of AAs from the aromatic group. Taken together our data show that AAs function as specific and selective signaling molecules in bone cells.

The effect of meals on bone turnover - a systematic review with focus on diabetic bone disease

INTRODUCTION

Type 2 diabetes is associated with an increased risk of bone fractures. Bone mineral density (BMD) is increased and bone turnover is low in type 2 diabetes and the increased BMD does not explain the increased fracture risk. However, the low bone turnover may lead to insufficient bone renewal with unrepaired micro-cracks and thus increase fracture risk. Ingestion of food acutely decreases bone resorption markers and the macronutrient composition of meals and meal frequency may influence bone metabolism adversely in subjects with unhealthy eating patterns, e.g., patients with type 2 diabetes.

AREAS COVERED

The treatment strategy of bone disease in type 2 diabetics is covered in this review. The current management of diabetic bone disease consists of anti-osteoporotic treatment. However, anti-resorptives may further reduce an already low bone turnover with uncertain effects. Furthermore, the acute and long-term effects of meal ingestion, weight loss alone and in combination with exercise as well as the possible underlying mechanisms are covered in this systematic review.

EXPERT COMMENTARY

Current management of diabetic bone disease is based on principles of anti-osteoporotic treatment in non-diabetic subjects. However, studies are urged to investigate whether anti-resorptives are equally beneficial in type 2 diabetes as in non-diabetic individuals.

Benefits and safety of dietary protein for bone health-an expert consensus paper endorsed by the European Society for Clinical and Economical Aspects of Osteopororosis, Osteoarthritis, and Musculoskeletal Diseases and by the International Osteoporosis Foundation

A summary of systematic reviews and meta-analyses addressing the benefits and risks of dietary protein intakes for bone health in adults suggests that dietary protein levels even above the current RDA may be beneficial in reducing bone loss and hip fracture risk, provided calcium intakes are adequate. Several systematic reviews and meta-analyses have addressed the benefits and risks of dietary protein intakes for bone health in adults. This narrative review of the literature summarizes and synthesizes recent systematic reviews and meta-analyses and highlights key messages. Adequate supplies of dietary protein are required for optimal bone growth and maintenance of healthy bone. Variation in protein intakes within the "normal" range accounts for 2-4% of BMD variance in adults. In older people with osteoporosis, higher protein intake (≥ 0.8-g/kg body weight/day, i.e., above the current RDA) is associated with higher BMD, a slower rate of bone loss, and reduced risk of hip fracture, provided that dietary calcium intakes are adequate. Intervention with dietary protein supplements attenuate age-related BMD decrease and reduce bone turnover marker levels, together with an increase in IGF-I and a decrease in PTH. There is no evidence that diet-derived acid load is deleterious for bone health. Thus, insufficient dietary protein intakes may be a more severe problem than protein excess in the elderly. Long-term, well-controlled randomized trials are required to further assess the influence of dietary protein intakes on fracture risk.

Very high-protein and low-carbohydrate enteral nutrition formula and plasma glucose control in adults with type 2 diabetes mellitus: a randomized crossover trial

BACKGROUND AND OBJECTIVES

Standard enteral nutrition (EN) formulas can  worsen hyperglycemia in diabetic patients. We hypothesized that altering the proportion of macronutrients in a formula; increasing protein while decreasing carbohydrate concentrations would improve glycemic response. The objective of this study was to demonstrate that an EN formula containing a very high concentration of protein (in the form of whey peptides) and low concentration of carbohydrate provide better control of postprandial blood glucose relative to a very high-protein/higher-carbohydrate formula.

SUBJECTS AND METHODS

This was a randomized crossover clinical trial of 12 ambulatory adult subjects with type 2 diabetes. The primary outcome was glycemic response following a bolus of isocaloric amounts of two EN formulas; the secondary outcome was insulin response. Subjects were randomized to the experimental or the control formula, on two separate days, 5-7 days apart.

RESULTS

Mean blood glucose concentrations at 10-180 min post-infusion and mean area under the curve for glucose over 240 min post-infusion were significantly lower with the experimental formula than with the control formula (71.99 ± 595.18 and 452.62 ± 351.38, respectively; p = 0.025). There were no significant differences in the mean insulin concentrations over time, insulinogenic indices, and first-phase insulin measurements.

CONCLUSIONS

An EN formula containing high-protein and low-carbohydrate loads can significantly improve glucose control in subjects with type 2 diabetes in ambulatory settings as evidenced by observed improved glucose control without significant difference in insulin response.

Three-Month Randomized Clinical Trial of Nasal Calcitonin in Adults with X-linked Hypophosphatemia

Previous work has demonstrated that a single subcutaneous dose of salmon calcitonin leads to a transient decline in circulating levels of FGF23 in patients with X-linked hypophosphatemia (XLH). Since the calcitonin receptor is expressed on osteocytes, this raises the possibility that interdicting signals through that receptor could modulate circulating levels of FGF23 in XLH. In the present study, 21 subjects with XLH were randomly assigned to receive either placebo nasal spray or 400 IU of nasal salmon calcitonin daily for three months. On the first and last day of the study, serial measurements of FGF23, 1,25-dihydroxyvitamin D, and TmP/GFR were made over 27 h. At the beginning of Visit 2 (the first day of month 2) and the beginning of Visit 3 (the first day of month 3), single, first-morning, fasting measurements of these same parameters were made before the next administered dose of study drug. Following the initial or final dose of study drug, there were no differences in area under the curve, based on treatment assignment, for the three principal outcome variables. Similarly, there were no differences in the fasting measures taken at the beginning of Visit 2 or Visit 3 compared to the fasting values on either day 2 of Visit 1 or the fasting values on day 2 of Visit 4. There were also no significant changes over time in serum phosphorus, serum calcium, circulating levels of PTH, CTx, or P1NP. The reasons why nasal salmon calcitonin did not recapitulate the findings with subcutaneously administered drug may relate to the kinetics of drug delivery, the bioavailability of drug or peak drug dose achieved. It remains possible, however, that other means of altering calcitonin receptor signaling may still provide an opportunity for regulating FGF23 production.

High protein consumption in trained women: bad to the bone?

Background

It has been posited that the consumption of extra protein (> 0.8 g/kg/d) may be deleterious to bone mineral content. However, there is no direct evidence to show that consuming a high-protein diet results in a demineralization of the skeleton. Thus, the primary endpoint of this randomized controlled trial was to determine if a high-protein diet affected various parameters of whole body and lumbar bone mineral content in exercise-trained women.

Methods

Twenty-four women volunteered for this 6-month investigation (n = 12 control, n = 12 high-protein). The control group was instructed to consume their habitual diet; however, the high-protein group was instructed to consume ≥2.2 g of protein per kilogram body weight daily (g/kg/d). Body composition was assessed via dual-energy x-ray absorptiometry (DXA). Subjects were instructed to keep a food diary via the mobile app MyFitnessPal®. Exercise or activity level was not controlled. Subjects were asked to maintain their current levels of exercise.

Results

During the 6-month treatment period, there was a significant difference in protein intake between the control and high-protein groups (mean±SD; control: 1.5±0.3, high-protein: 2.8±1.1 g/kg/d); however, there were no differences in the consumption total calories, carbohydrate or fat. Whole body bone mineral density did not change in the control (pre: 1.22±0.08, post: 1.22±0.09 g/cm²) or high-protein group (pre: 1.25±0.11, post: 1.24±0.10 g/cm²). Similarly, lumbar bone mineral density did not change in the control (pre: 1.08±0.16, post: 1.05±0.13 g/cm²) or high-protein group (pre: 1.07±0.11, post: 1.08±0.12 g/cm²). In addition, there were no changes in whole body or lumbar T-Scores in either group. Furthermore, there were no changes in fat mass or lean body mass.

Conclusion

Despite an 87% higher protein intake (high-protein versus control), 6 months of a high-protein diet had no effect on whole body bone mineral density, lumbar bone mineral density, T-scores, lean body mass or fat mass.

Effects of Protein, Essential Amino Acids, B-Hydroxy B-Methylbutyrate, Creatine, Dehydroepiandrosterone and Fatty Acid Supplementation on Muscle Mass, Muscle Strength and Physical Performance in Older People Aged 60 Years and Over. A Systematic Review on the Literature

OBJECTIVES

The objective of this study was to perform a systematic review to investigate the effects protein, essential amino acids (EAA), β-hydroxy β-methylbutyrate (HMB), creatine, dehydroepiandrosterone (DHEA) and fatty acid supplementation on muscle mass, muscle strength and physical performance of elderly subjects.

METHODS

Using the electronic databases MEDLINE and EMBASE we identified RCTs published until February 2016 which assessed the effects of these nutrient supplementation on muscle strength, muscle mass or physical performance. Study selection and data extraction were performed by two independent reviewers.

RESULTS

Search strategy allowed us to identify 23 RCTs. Among them, four used proteins as nutritional supplement, seven EAAs, six creatine, four DHEA and finally, two HMB. From our systematic review, it seems that the effects of these supplementations on muscle health are rather limited. Only consistent effects of EAA supplementation on physical performance (3 out of the 4 RCTs using EAA supplementation found significant effect of this supplementation on physical performance) and HMB supplementation on muscle mass (all the 2 identified RCTs using HMB supplementation found significant effect of this supplementation on muscle mass) have been found across studies. No consistent effects were found for the other types of dietary supplementation. Because of the important limitations in study design, inconsistency and lack of directness, the overall quality of the evidence was judged to be low or very low using the GRADE system.

CONCLUSION

This systematic review showed a limited effect of nutritional supplementation on muscle mass, muscle power and physical function. Inconsistent positive effects were observed for some specific supplementations but the results only concerned one aspect of the muscle. Well designed and appropriately powered RCTs are needed to provide evidence for appropriate clinical recommendations.

High dairy protein intake is associated with greater bone strength parameters at the distal radius and tibia in older men: a cross-sectional study

Dairy protein but not plant protein was associated with bone strength of the radius and tibia in older men. These results are consistent with previous results in women and support similar findings related to fracture outcomes. Bone strength differences were largely due to thickness and area of the bone cortex.

INTRODUCTION

Our objective was to determine the association of protein intake by source (dairy, non-dairy animal, plant) with bone strength and bone microarchitecture among older men.

METHODS

We used data from 1016 men (mean 84.3 years) who attended the Year 14 exam of the Osteoporotic Fractures in Men (MrOS) study, completed a food frequency questionnaire (500-5000 kcal/day), were not taking androgen or androgen agonists, and had high-resolution peripheral quantitative computed tomography (HR-pQCT) scans of the distal radius and distal or diaphyseal tibia. Protein was expressed as percentage of total energy intake (TEI); mean ± SD for TEI = 1548 ± 607 kcal/day and for total protein = 16.2 ± 2.9%TEI. We used linear regression with standardized HR-pQCT parameters as dependent variables and adjusted for age, limb length, center, education, race/ethnicity, marital status, smoking, alcohol intake, physical activity level, corticosteroids use, supplement use (calcium and vitamin D), and osteoporosis medications.

RESULTS

Higher dairy protein intake was associated with higher estimated failure load at the distal radius and distal tibia [radius effect size = 0.17 (95% CI 0.07, 0.27), tibia effect size = 0.13 (95% CI 0.03, 0.23)], while higher non-dairy animal protein was associated with higher failure load at only the distal radius. Plant protein intake was not associated with failure load at any site.

CONCLUSION

The association between protein intake and bone strength varied by source of protein. These results support a link between dairy protein intake and skeletal health, but an intervention study is needed to evaluate causality.

High Dietary Protein Intake and Protein-Related Acid Load on Bone Health

PURPOSE OF REVIEW

Consumption of high-protein diets is increasingly popular due to the benefits of protein on preserving lean mass and controlling appetite and satiety. The paper is to review recent clinical research assessing dietary protein on calcium metabolism and bone health.

RECENT FINDINGS

Epidemiological studies show that long-term, high-protein intake is positively associated with bone mineral density and reduced risk of bone fracture incidence. Short-term interventional studies demonstrate that a high-protein diet does not negatively affect calcium homeostasis. Existing evidence supports that the negative effects of the acid load of protein on urinary calcium excretion are offset by the beneficial skeletal effects of high-protein intake. Future research should focus on the role and the degree of contribution of other dietary and physiological factors, such as intake of fruits and vegetables, in reducing the acid load and further enhancing the anabolic effects of protein on the musculoskeletal system.

Dietary Protein Intake above the Current RDA and Bone Health: A Systematic Review and Meta-Analysis

Dietary intake of protein is fundamental for optimal acquisition and maintenance of bone across all life stages; however, it has been hypothesized that intakes above the current recommended dietary allowance (RDA) might be beneficial for bone health. We utilized the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines when preparing and reporting this systematic review and meta-analysis. A literature search strategy through April 11, 2017, was developed for the following 3 databases: PubMed, Ovid Medline, and Agricola. Included studies were those randomized controlled trials and prospective cohort studies among healthy adults ages 18 and older that examined the relationships between varying doses of protein intake at or above the current U.S. RDA (0.8 g/kg/d or 10%-15% of total caloric intake) from any source on fracture, bone mineral density (BMD)/bone mineral content (BMC), and/or markers of bone turnover. Twenty-nine articles were included for data extraction (16 randomized controlled trials [RCTs] and 13 prospective cohort studies). Meta-analysis of the prospective cohort studies showed high vs low protein intakes resulted in a statistically significant 16% decrease in hip fractures (standardized mean difference [SMD] = 0.84, 95% confidence interval [CI], 0.73, 0.95; I² = 36.8%). Data from studies included in these analyses collectively lean toward the hypothesis that protein intake above the current RDA is beneficial to BMD at several sites. This systematic review supports that protein intakes above the current RDA may have some beneficial role in preventing hip fractures and BMD loss. There were no differences between animal or plant proteins, although data in this area were scarce. Larger, long-term, and more well-controlled clinical trials measuring fracture outcomes and BMD are needed to adequately assess whether protein intake above the current RDA is beneficial as a preventative measure and/or intervention strategy for osteoporosis. Key teaching points: • • Bone health is a multifactorial musculoskeletal issue, and optimal protein intakes are key in developing and maintaining bone throughout the life span. • • Dietary protein at levels above the current RDA may be beneficial in preventing hip fractures and BMD loss. • • Plant vs animal proteins do not seem to differ in their ability to prevent bone loss; however, data in this area are scarce. • • Larger, long-term RCTs using women not using hormone replacement therapy (HRT) are needed to adequately assess the magnitude of impact that protein intakes above the RDA have on preventing bone loss.

The relationship between protein quantity, BMD and fractures in older adults

BACKGROUND

Previously, no large-scale literature reviews have focussed on the relationship between dietary protein and its impact on bone mineral density (BMD) and fracture risk-as measures of bone health-in older adults and its potential impact as a primary prevention tool.

AIMS

The aim of this study was to assess the impact of varying dietary protein levels on bone health.

METHODS

A literature review of trials concerning older adults' (>50 years of age) and animals' varying protein intake in the diet and its effect on BMD (human and animal) and fracture risk (human only) was carried out. Additionally, a review of dietary assessment tools used in these studies was also analysed.

RESULTS

Ten out of fourteen trials assessing BMD and dietary protein quantity in humans and 3/4 in animal trials found a positive relationship between these two parameters. Four out of seven trials investigating the relationship between dietary protein quantity and fracture risk displayed a positive, protective effect of dietary protein levels on fracture risk. Sixty-two percent of studies used the Food-Frequency Questionnaire assessment method.

DISCUSSION

Increased protein intake in the diet is beneficial to bone health and reduces morbidity and mortality. The importance of using dietary protein, along with calcium and vitamin D, as a primary preventative strategy should be stressed, given the health and cost benefits that this would deliver, with a possible need for a higher level of protein in the diet of an elderly person than what is currently recommended.