Comparing Even with Skewed Dietary Protein Distribution Shows No Difference in Muscle Protein Synthesis or Amino Acid Utilization in Healthy Older Individuals: A Randomized Controlled Trial

Effect of breakfast protein intake on muscle mass and strength in adults: a scoping review

BACKGROUND

The distribution of protein intake throughout the day is frequently skewed, with breakfast having the lowest protein intake across all age groups. There is no review that addresses the association between breakfast protein intake and muscle mass and strength.

OBJECTIVE

This scoping review aims to summarize the literature on the relationship between protein intake during breakfast and muscle mass and strength in adults.

METHODS

This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. Two independent reviewers screened and appraised the articles identified from 3 electronic databases (Medline, Web of Science, and Scopus) that focused on protein intake per meal and its impact on muscle-related outcomes.

RESULTS

A total of 14 763 articles were retrieved from 3 databases, and after the screening process, 15 articles were included for analysis. Approximately 58.8% of findings from 11 studies examining the association between high protein intake during breakfast and muscle mass indicated an increase in muscle mass among participants. Half of 6 studies (50.0%) exploring the relationship between high protein intake at breakfast and muscle strength demonstrated an increase in muscle strength. Consuming high amounts of protein at breakfast or more protein in the morning than in the evening was associated with an increase in the skeletal muscle index and lean body mass.

CONCLUSION

Protein consumption at breakfast revealed potential benefits in increasing muscle mass across 5 studies involving an elderly population and 2 studies encompassing middle-aged women and young men in our review. However, the relationship between protein intake at breakfast and muscle strength remains unclear. Further high-quality randomized controlled trials are required to examine whether adults can preserve skeletal muscle health outcomes by consuming higher amounts of protein at breakfast.

Effect of 3 Different Daily Protein Intakes in a 2-Meal Eating Pattern on Protein Turnover in Middle Age and Older Adults: A Randomized Controlled Trial

BACKGROUND

Reduced meal frequency patterns have become popular for weight loss, maintenance, and improving cardiometabolic health. The extended fasting windows with these dietary patterns could lead to greater protein breakdown, which is a concern for middle-aged and older adults who may need higher protein intakes to maintain or increase net protein balance.

OBJECTIVES

This study aimed to quantify muscle and whole-body protein kinetic responses to 3 different daily protein intakes within a 2-meal eating pattern.

METHODS

Thirty participants (age: 61 ± 6 y, BMI: 26.5 ± 4.8 kg/m2) participated in this 24-h metabolic study using oral stable isotope tracer techniques and were randomized to 1 of 3 protein intakes: 1) recommended dietary allowance (RDA): 0.8 g/kg/d; 2) habitual United States intake: 1.1 g/kg/d; or 3) ≈2RDA: 1.5 g/kg/d distributed across 2 meals, consumed within a 9-h window.

RESULTS

Whole-body net protein balance was significantly higher for 1.5 g/kg/d compared with 0.8 g/kg/d [mean difference: 0.55 g/kg; lean body mass (LBM)/d; 95% confidence interval (CI): 0.17, 0.93 g/kg LBM/d; P = 0.004] and 1.1 g/kg/d (mean difference: 0.6 g/kg LBM/d; 95%CI: 0.23, 0.97 g/kg LBM/d; P = 0.001), with no difference between 0.8 and 1.1 g/kg/d (mean difference: 0.05 g/kg LBM/d; 95%CI: -0.31, 0.40 g/kg LBM/d; P = 0.936). Muscle protein synthesis was not significantly different between any groups (P = 0.388).

CONCLUSION

s: Within a 2-meal eating pattern, a protein intake of 1.5 g/kg/d led to a more positive whole-body net protein balance than intakes of 0.8 and 1.1 g/kg/d in middle-aged and older adults. This trial was registered at clinicaltrials.gov as NCT04830514.

Association between mealtime distribution of macronutrient and mental health in apparently healthy Iranian adults: a cross-sectional study

Mental health (MH) disorders are one of the most prevalent global public health issues for a significant portion of the population. The aim of this study was to investigate the relationship between the mealtime distribution of macronutrients and MH in Iranian adults. We used a convenience sampling technique to perform this cross-sectional study. The Depression, Anxiety, and Stress Scale (DASS-21) was used to assess the MH outcome. Dietary consumption was assessed using multiple 24-hour dietary recalls. The coefficient of variation (CV) was then used to compute the macronutrient distribution at mealtime. In all, 54.6%, 53.9%, and 56.6% were classified as having anxiety, depression, and stress symptoms, respectively. The CV scores for carbohydrate were relatively evenly distributed across all meal times, with a mean of 0.38, 0.38, and 0.39 for breakfast, lunch, and dinner, respectively. We observed no significant association between the mealtime distribution of carbohydrates and mental health indices in any of the analyzed models. However, a more skewed distribution of protein intake towards dinner (i.e. a higher protein CV value) was positively associated with anxiety (OR: 1.69; CI: 1.02-2.78) and stress symptoms (OR: 1.93; CI: 1.17-3.16). We also observed a significant association between fat distribution and depression symptoms, with subjects in tertile 2 having higher odds of depression compared to T1 (OR: 1.63; CI: 1.00-2.63). In conclusion, a skewed distribution of protein and fat intake may be associated with mental health problems. Future studies are warranted to validate these findings and gain a better understanding of the underlying mechanisms.

Short-term intermittent fasting and energy restriction do not impair rates of muscle protein synthesis: A randomised, controlled dietary intervention

BACKGROUND

Intermittent fasting (IF) is an effective energy restricted dietary strategy to reduce body and fat mass and improve metabolic health in individuals with either an overweight or obese status. However, dietary energy restriction may impair muscle protein synthesis (MPS) resulting in a concomitant decline in lean body mass. Due to periods of prolonged fasting combined with irregular meal intake, we hypothesised that IF would reduce rates of MPS compared to an energy balanced diet with regular meal patterns.

AIMS

We assessed the impact of a short-term, ten days, alternate day fasting or a continuous energy restricted diet to a control diet on integrated rates of skeletal MPS in middle-aged males with overweight or obesity.

METHODS

Twenty-seven middle-aged males with overweight or obesity (age: 44.6 ± 5.4 y; BMI: 30.3 ± 2.6 kg/m2) consumed a three-day lead-in diet, followed by a ten-day controlled dietary intervention matched for protein intake, as alternate day fasting (ADF: 62.5 energy (En)%, days of 25 En% alternated with days of 100 En% food ingestion), continuous energy restriction (CER: 62.5 En%), or an energy balanced, control diet (CON: 100 En%). Deuterated water (D2O) methodology with saliva, blood, and skeletal muscle sampling were used to assess integrated rates of MPS over the ten-day intervention period. Secondary measures included fasting plasma glucose, insulin, and gastrointestinal hormone concentrations, continuous glucose monitoring, and assessment of body composition.

RESULTS

There were no differences in daily rates of MPS between groups (ADF: 1.18 ± 0.13, CER: 1.13 ± 0.16, and CON: 1.18 ± 0.18 %/day, P > 0.05). The reductions in body mass were greater in ADF and CER compared to CON (P < 0.001). Lean and fat mass were decreased by a similar magnitude across groups (main time effect, P < 0.001; main group effect, P > 0.05). Fasting plasma leptin concentrations decreased in ADF and CER (P < 0.001), with no differences in fasting plasma glucose or insulin concentrations between groups.

CONCLUSION

Short-term alternate day fasting does not lower rates of MPS compared to continuous energy restriction or an energy balanced, control diet with matched protein intake. The prolonged effects of IF and periods of irregular energy and protein intake patterns on muscle mass maintenance remain to be investigated. This trial was registered under Australian New Zealand Clinical Trial Registry (https://www.anzctr.org.au), identifier no. ACTRN12619000757112.

Distribution of daily protein intake and appendicular skeletal muscle mass in healthy free-living Chinese older adults

AIMS

Evidence regarding impact of protein intake distribution on skeletal muscle mass in older adults is limited and inconsistent. This study aims to investigate the relationship of evenness of dietary protein distribution and number of meals exceeding a threshold with appendicular skeletal muscle mass (ASM) in healthy and free-living Chinese older adults.

METHODS

Repeated measured data of 5689 adult participants aged ≥ 60 years from the China Health and Nutrition Survey (CHNS) 2015 and 2018 waves were analyzed. Mixed-effects linear regression model was performed to examine the relationship between coefficient of variance (CV) of protein intake across meals, number of meals ≥ 0.4 g protein/kg BW and ASM, respectively. Analyses were conducted separately for male and female.

RESULTS

The average CV of protein intake in each wave was in the range of 0.34-0.35. More than 40% male and female participants in each wave had no meal reaching 0.4 g protein/kg BW. Female participants in the highest quartile of protein intake CV had significantly lower ASM (β = -0.18, 95%CI = -0.32, -0.04) compared with those in the lowest quartile, after adjustment for multiple confounders. Significant negative trends were observed across dietary protein CV quartiles with ASM both in male (P trend = 0.043) and female (P trend = 0.007). Significant positive association between number of meals exceeding 0.4 g protein /kg BW and relative ASM were observed in females (2 meals vs. 0 meal: β = 0.003, 95%CI = 0.0007,0.006;≥3 meals vs. 0 meal: β = 0.008, 95%CI = 0.003,0.013), after adjusting for multiple covariates.

CONCLUSIONS

A more even-distributed protein intake pattern and more meals reaching protein intake threshold were respectively associated with higher appendicular skeletal muscle mass in healthy and free-living older Chinese adults. Prospective studies and intervention trials are needed to confirm these cross-sectional findings.

Even or skewed dietary protein distribution is reflected in the whole-body protein net-balance in healthy older adults: A randomized controlled trial

BACKGROUND & AIM

For older adults, the dietary protein intake has shown to be skewed towards the evening meal. Resultingly, the vital source of essential amino acids could be insufficient after some meals, while after the evening meal the dietary protein could be suboptimally utilized for protein synthesis. The present study explored if an even distribution of the protein intake could improve the dietary amino acid absorption and whole-body protein net-balance.

METHODS

Twenty-four healthy elderly males and females were included in a randomized controlled trial. Ten days of habituation to either an EVEN (n = 12) or SKEWED (n = 12) protein intake, was followed by a trial day. The total protein intake was controlled at 1.5 g/kg LBM, divided into 30% at each main meal in EVEN, and into 15% at breakfast and lunch and 60% at dinner in SKEWED. Snacks with 5% of the protein intake were served between meals. Energy intake in the meals and snacks were equal in both groups. Intrinsically labelled ²H₅-phenylalanine minced meat was served as the dietary protein to assess the amino acid absorption. On the trial day, infusion of ²H₈-phenylalanine and ²H₂-tyrosine, and blood samples taken over 11 h were used to measure whole-body protein turnover. Vastus lateralis muscle biopsies were taken to measure 9 h muscle protein FSR.

RESULTS

Amino acid absorption rates and concentrations were greater in EVEN compared to SKEWED protein intake. Whole-body protein breakdown rates were lower with similar protein synthesis rates, and consequently the net-balance was greater in EVEN after breakfast and lunch compared to SKEWED and were the same in both groups after dinner. Muscle protein FSR were not different between EVEN and SKEWED.

CONCLUSIONS

The whole-body protein net-balance was more positive in EVEN compared to SKEWED for an extended time of the measured period, driven by a lower whole-body protein breakdown in EVEN.

CLINICAL TRIALS REGISTRATION

NCT03870425, https://clinicaltrials.gov/ct2/show/NCT03870425.