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Background: Consensus regarding the required intake of indispensable amino acids (IDAAs) and protein (representing total AAs) in the adult is lacking. Oxidation is a major, though not exclusive, source of IDAA loss in the human body and a primary factor determining requirements; a quantitative understanding of oxidative IDAA losses is required., Objective: To develop a factorial diurnal model of total oxidative IDAA and protein losses in the adult human., Methods: A factorial diurnal model of oxidative losses of protein and each IDAA at maintenance was developed by estimating the magnitude and variability of sources of oxidative loss from existing literature: inevitable catabolism (constitutive oxidation of each absorbed dietary AA), and protein turnover in the postprandial and postabsorptive states. Total oxidative losses were calculated by summing individual losses, validated against published independent nitrogen balance data and compared to current IDAA requirements., Results: The factorial model predicted minimum oxidative total AA losses of 390±60 mg.kgBW -1 .day -1 , 59% of the EAR for protein. Inevitable AA oxidation and oxidation associated with postabsorptive protein turnover were the major sources of the oxidative loss for protein, at 40% and 44%, respectively. Summed oxidative IDAA losses ranged from 64% (isoleucine) to 91% (tryptophan) of current requirements. Total oxidative losses predicted by the model were significant predictors of actual experimental oxidative losses obtained by nitrogen balance (R 2 =0.66; p=0.049)., Conclusions: The use of a factorial model for estimation of minimum IDAA and protein oxidative losses in the adult human provides an essential starting point for an updated understanding of protein and IDAA requirements. Further iterations of the model will estimate total protein and IDAA requirements, and account for variations in dietary protein quantity and quality, as well as different populations and physiological states. Additional data, especially for inevitable oxidation in humans, and particularly with respect to individual IDAAs, are needed., Competing Interests: Conflicts of interest Robert R Wolfe is a shareholder in The Amino Company, LLC, holds US patents for essential amino acid compositions, and has received grants from the National Cattleman's Beef Association., (Copyright © 2024. Published by Elsevier Inc.)

The present study investigated the effects of different dietary protein levels on the growth and survival of milkfish Chanos chanos for 90 days feeding trial. Milkfish with an average body weight of 10.81 ± 0.07 g were collected from the coastal zone using a manual dragnet. The study tested four diets, 10% (T1), 15% (T2), 30% (T3) and 38% (T4) of proteins containing feed with triplicates. These diets were offered to the milkfish juveniles in triplicate earthen ponds (1.5 ha). Juveniles were stocked at 10,000 ind./1.5 ha, and initially feeding rate of 10% biomass per day. The feeding rate adjusted according to fish biomass on a weekly basis. The present results showed that fishes fed 30% of proteins-containing feed have the highest weight gain (WG), specific growth rate (SGR), average daily weight gain (ADWG), survival, and the best feed conversion ratio (FCR) compared to the other treatments. The present study suggested that 30% crude protein is the optimum level for the best growth performance and for obtaining a high yield of milkfish C. chanos reared in the brackish water ponds.

In wealthy countries, the protein intake of adults is usually considered to be adequate, and considerations of protein quality are often deemed irrelevant. The objective was to examine dietary protein intakes of adults in developed countries in the context of dietary protein quality. An analysis of NHANES population data on actual protein intakes in the United States (a developed country) demonstrated that for a dietary Digestible Indispensable Amino Acid Score (DIAAS) of 100%, 11% of the adult (19-50 y) population had habitual protein intakes below the Estimated Average Requirement (EAR) and 22% below the Recommended Dietary Allowance. The percentage of the population with utilizable protein intakes potentially falling below the EAR increased as the assumed DIAAS declined. Analysis of the NHANES data and several other datasets also indicated that total protein intakes can be limiting or close to limiting for the elderly and some vegetarians and vegans. Here, lower dietary protein quality can potentially lead to inadequate utilizable protein intakes. For many people in specific physiological states (e.g., weight loss, endurance sports, resistance exercise) attempting to meet higher dietary protein targets often with accompanying lowered energy intakes, low dietary protein quality can lead to protein calories expressed as a proportion of total calories, falling outside what may be acceptable limits (maximum of 30% protein calories from total calories). In general, individuals within the adult population may be susceptible to macronutrient imbalance (whenever total protein intakes are high, daily energy intakes low) and for diets with lower protein quality (DIAAS <100%). Our analysis shows that dietary protein quality is relevant in mid- to high-income countries., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Because of the production of nutrient-deficient infant formulas (IFs), the United States Congress passed regulations on the composition and production of IF, referred to as the Infant Formula Act (IFA), in 1980, which was amended in 1986. More detailed FDA rules have been created since then, specifying the ranges or minimum intakes of nutrients and providing details for the safe production and evaluation of infant formulas. Although generally effective in ensuring safe IF, recent events have made it clear that a re-evaluation of aspects of all the nutrient composition regulations for IF is needed, including consideration of adding requirements related to bioactive nutrients not mentioned in the IFA. We propose that, as principal examples, the requirement for iron content needs to be re-evaluated and that DHA and AA should be considered for addition to the nutrient requirements after scientific review by a panel such as those established by the National Academies of Sciences, Engineering, and Medicine. Additionally, there is no specific requirement in current FDA regulations for the energy density of IF, and this should be added alongside potential revisions of the protein requirement. It would also be ideal to have specific FDA rules on nutrient intakes for premature infants as these are exempted from the specific nutrient regulations of the amended IFA., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Lifelong dietary treatment is recommended in the management of phenylketonuria (PKU). Accordingly, an increasing adult population require age-specific PKU guidelines on protein requirements to support changing metabolic demands across the lifespan. Given that protein intake for dietary management of PKU is primarily (52-80%) derived from protein substitutes, the prescribing practice of protein substitutes must be underpinned by robust evidence. Whilst dietary guidelines for PKU management is evolving to incorporate adult specific protein recommendations, the scientific evidence underpinning these guidelines is currently limited. Instead, the determination of protein requirements for people with PKU have previously been extrapolated from estimates derived from the general healthy population, based on arguably outdated nitrogen balance methodology. Furthermore, a compensatory factor of 20-40% has been incorporated to account for the reduced uptake and utilisation of the elemental amino acids contained in protein substitutes. However, research informing this compensatory factor has been conducted in younger adults, with the majority of studies in non-PKU individuals. Given extensive evidence that the muscle anabolic response to ingested protein is impaired in older vs. young adults, the validity of current dietary protein recommendations for adults and older adults with PKU has been challenged. This narrative review aims to critically evaluate the existing scientific evidence underpinning current guidelines on protein requirements for adults with PKU, highlighting existing gaps in knowledge and directions for future research. We argue that current guidelines on protein requirements need updating to optimise long-term physical and functional outcomes in older adults with PKU., Competing Interests: Conflict of interest SF has received funding to attend conferences and study days from Nutricia, Vitaflo International and Dr. Schär UK Ltd, and consulting fees from Vitaflo International and Meta Healthcare Ltd., (Copyright © 2020 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)

Background & Aims: Assessing the ability to respond anabolic to dietary protein intake during illness provides important insight in the capacity of lean body mass maintenance. We applied a newly developed stable tracer approach to assess in one session in patients with chronic obstructive pulmonary disease (COPD) and healthy older adults both the minimal amount of protein intake to obtain protein anabolism (anabolic threshold) and the efficiency of dietary protein to promote protein anabolism (anabolic capacity)., Methods: We studied 12 clinically and weight stable patients with moderate to very severe COPD (mean ± SE forced expiratory volume in 1 s: 36 ± 3% of predicted) and 10 healthy age-matched older adults. At 2-h intervals and in consecutive order, all participants consumed a mixture of 0.0, 0.04, 0.10 and 0.30 g hydrolyzed casein protein×kg ffm -1 ×2 h -1 and carbohydrates (2:1). We assessed whole body protein synthesis (PS), breakdown (PB), net PS (PS-PB) and net protein balance (phenylalanine (PHE) intake - PHE to tyrosine (TYR) hydroxylation) by IV primed and continuous infusion of L-[ring- 2 H 5 ]PHE and L-[ 13 C 9 , 15 N]-TYR. Anabolic threshold (net protein balance = 0) and capacity (slope) were determined on an individual basis from the assumed linear relationship between protein intake and net protein balance., Results: We confirmed a linear relationship between protein intake and net protein balance for all participants (R 2 range: 0.9988-1.0, p ≤ 0.0006). On average, the anabolic threshold and anabolic capacity were comparable between the groups (anabolic threshold COPD vs. healthy: 3.82 ± 0.31 vs. 4.20 ± 0.36 μmol PHE × kg ffm -1  × hr -1 ; anabolic capacity COPD vs. healthy: 0.952 ± 0.007 and 0.954 ± 0.004). At protein intake around the anabolic threshold (0.04 and 0.10 g protein×kg ffm -1 ×2 h -1 ), the increase in net PS resulted mainly from PB reduction (p < 0.0001) whereas at a higher protein intake (0.30 g protein×kg ffm -1 ×2 h -1 ) PS was also stimulated (p < 0.0001)., Conclusions: The preserved anabolic threshold and capacity in clinically and weight stable COPD patients suggests no disease related anabolic resistance and/or increased protein requirements., Trial Registry: ClinicalTrials.gov; No. NCT01734473; URL: www.clinicaltrials.gov., (Copyright © 2018 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)

Background: The 2007 World Health Organization/Food and Agriculture Organization/United Nations University (WHO/FAO/UNU) recommendation for the Estimated Average Requirement (EAR) of additional protein during pregnancy for a gestational weight gain (GWG) of 12 kg (recalculated from a GWG of 13.8 kg) is 6.7 and 21.7 g/d in the second and the third trimester, respectively. This EAR is based on measurements of potassium accretion in high-income country (HIC) pregnant women. It is not known if low- to middle-income country, but well-nourished, pregnant women have comparable requirements., Objective: We aimed to estimate total body potassium (TBK) accretion during pregnancy in Indian pregnant women, using a whole-body potassium counter (WBKC), to measure their additional protein EAR., Methods: Well-nourished pregnant women (20-40 y, n = 38, middle socioeconomic stratum) were recruited in the first trimester of pregnancy. Anthropometric, dietary, and physical activity measurements, and measurements of TBK using a WBKC, were performed at each trimester and at birth., Results: The mid-trimester weight gain was 2.7 kg and 8.0 kg in the second and the third trimester, respectively, for an average 37-wk GWG of 10.7 kg and a mean birth weight of 3.0 kg. Protein accretion was 2.7 and 5.7 g/d, for an EAR of 8.2 and 18.9 g/d in the second and the third trimester, respectively. The additional protein EAR, calculated for a GWG of 12 kg, was 9.1 and 21.2 g/d in the second and the third trimester, respectively., Conclusion: The additional protein requirements of well-nourished Indian pregnant women for a GWG of 12 kg in the second and third trimesters were similar to the recalculated 2007 WHO/FAO/UNU requirements for 12 kg., (Copyright © American Society for Nutrition 2019.)

Protein quality scores use the amino acid (AA) requirements of a healthy North American child. AA requirements vary with physiologic status. We estimated AA requirements for healthy North American children, children with environmental enteric dysfunction, children recovering from wasting, and children with an acute infection. The protein quality of food aid products was then calculated to determine whether it was sufficient in all these groups, and we found that it may not be adequate for all of them. Physiologic status is important when assessing the protein quality of food aid. Rates of weight gain from 8 published trials treating children with moderate acute malnutrition were abstracted, and protein quality scores from the corresponding food aid products were calculated with the use of the digestible indispensable amino acid score (DIAAS). Two DIAAS values were calculated, one in healthy children aged 1-3 y as a reference population and the other in malnourished children aged 1-3 y as a reference population. These data were used to calculate the best fit regression line between weight gain and protein quality. The slope of the regression line was greater when malnourished children were used as a reference population than when healthy children were used (0.128; 95% CI: 0.118, 0.138 compared with 0.097; 95% CI: 0.090, 0.105 measured in g · kg -1 · d -1 · DIASS U -1 ). These findings suggest that adjusting AA requirements for physiologic status may more accurately estimate the minimum protein quality of food aid products., (© 2017 American Society for Nutrition.)

Background & Aims: Energy targets are a matter of debate for intensive care (ICU) patients. As the guidelines have evolved, energy targets have been reduced, while the protein intake objectives have increased. The impact of these changes remains largely unknown. This quality study aimed at investigating the clinical impact of these changes in patients with an ICU stay >3 days., Methods: Observational cohort study over two 3 months periods (A, B), with distinct prevailing nutrition recommendations in patients admitted consecutively to a multidisciplinary ICU. Inclusion criterion: ICU stay >3 days. Recorded variables: severity scores, energy target and delivery, protein delivery, feeding route, length of stay (ICU, hospital) and hospital outcome. Data as mean, SD and IQR., Results: The analysis included 389 patients, and 3920 observation days. Except for patient age (A versus B: 57.8 and 62.3 years; p = 0.010) and NRS (4.3 vs 3.9 respectively p = 0.002), the cohorts were similar. Compared to A, the mean prescribed energy target decreased by 125 kcal (1947 kcal/d vs. 1822 kcal*day -1 respectively), resulting in lower energy delivery (1353 kcal*day -1 vs. 1238 kcal*day -1 ; p < 0.0001), and reduced protein delivery (81 g*day -1 vs. 65 g*day -1 : p < 0.0001). These differences were associated in survivors with prolonged mechanical ventilation (5.0 days vs. 6.7 days; p = 0.004), extended ICU stay (8.5 vs. 9.9 days; p = 0.0036), and longer hospital stay (23.4 vs. 26.4 days respectively; p = 0.028). Mortality was unchanged., Conclusions: A linear reduction in energy target recommendation without changing the feed composition led to an unplanned and significant reduction in protein delivery, which was associated with a prolonged duration of ventilation and an extended hospital stay., (Copyright © 2016 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)

Background: Phenylketonuria is characterized by mutations in the Phe hydroxylase gene that leads to the accumulation of Phe in plasma and the brain. The standard of care for phenylketonuria is nutritional management with dietary restriction of Phe and the provision of sufficient protein and energy for growth and health maintenance. The protein requirement in children with phenylketonuria is empirically determined based upon phenylketonuria nutritional guidelines that are adjusted individually in response to biochemical markers and growth., Objective: We determined dietary protein requirements in children with phenylketonuria with the use of the indicator amino acid oxidation (IAAO) technique, with l-[1- 13 C]Leu as the indicator amino acid., Methods: Four children (2 males; 2 females) aged 9-18 y with phenylketonuria [mild hyperphenylalanemia (mHPA); 6-10 mg/dL (360-600 μmol/L)] were recruited to participate in ≥7 separate test protein intakes (range: 0.2-3.2 g ⋅ kg -1 ⋅ d -1 ) with the IAAO protocol with the use of l-[1- 13 C]Leu followed by the collection of breath and urine samples over 8 h. The diets were isocaloric and provided energy at 1.7 times the resting energy expenditure. Protein was provided as a crystalline amino acid mixture based on an egg protein pattern, except Phe and Leu, which were maintained at a constant across intakes. Protein requirement was determined with the use of a 2-phase linear-regression crossover analysis of the rate of l-[1- 13 C]Leu tracer oxidation., Results: The mean protein requirement was determined to be 1.85 g ⋅ kg -1 ⋅ d -1 (R 2 = 0.66; 95% CI: 1.37, 2.33). This result is substantially higher than the 2014 phenylketonuria recommendations (1.14-1.33 g ⋅ kg -1 ⋅ d -1 ; based on 120-140% above the current RDA for age)., Conclusions: To our knowledge, this is the first study to directly define a quantitative requirement for protein intake in children with mHPA and indicates that current protein recommendations in children with phenylketonuria may be insufficient. This trial was registered at clinicaltrials.gov as NCT01965691., (© 2017 American Society for Nutrition.)

Infant formulas have historically been developed based on providing macronutrients at intake concentrations approximately matching the composition of human milk. In most countries, targets of 1.4-1.5 g of protein/dL and 20 kcal/oz (67-68 kcal/dL) have been set as the protein and energy concentrations for formulas during the first year of life, although this may be an overestimation of these contents. Recent introduction of lower-protein and -energy formulas in full-term infants led us to systematically review the literature for its effects on growth. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, our inclusion criteria were studies that enrolled healthy full-term infants and evaluated lower-protein or lower-energy formula, reported anthropometric outcomes including weight and length, and followed infants for at least 6 mo. Six studies were eligible for inclusion. These studies varied in the content of nutrients provided in the intervention and control groups, by additional dietary components in the study groups, and the timing and length of the intervention, which limit their usefulness for interpreting newly introduced lower-protein and -energy formulas in the United States. These studies suggest adequate growth during infancy and early childhood with infant formulas with concentrations of protein and energy slightly below historical standards in the United States. Further long-term research is needed to assess the impact of the use of lower-protein and/or lower-energy products, especially for nutritionally at-risk populations such as preterm infants and infants who are born small for gestational age., (© 2015 American Society for Nutrition.)