Amino Acids In Children Research Articles

Precision Nutrition – Evaluating Dietary Protein and Amino Acid Intake among Children Using Duplicate Dietary Samples

Introduction: Precision nutrition, at the intersection of science and health, offers tailored dietary intervention, particularly vital for vulnerable populations like children. Focusing on protein and essential amino acids (AA), crucial for health, personalized approaches are keys for addressing deficiencies, and moving beyond generalized methods. While research on the dietary duplication technique has explored various nutrients, but there is a gap in understanding its use for assessing protein and amino acid intake, especially in children. Aim: The study aims to use the dietary duplication technique to assess the precise dietary intake of protein and AA in children, focusing on determining their exact portions and analyzing duplicate samples for content. Methods: A cross-sectional study in Chennai involved 12 children aged 4–9 years. Duplicate food portions for a day were collected from mothers in low-density polythene bags. Samples were analyzed for protein and amino acid content in a National Accreditation Board for Testing and Calibration Laboratories-accredited laboratory. Results: Girls exhibited deficient levels of histidine, lysine, phenylalanine, threonine, and tryptophan, while isoleucine met the Recommended Dietary Allowances threshold. A t-test showed significant differences in threonine levels among 4–6-year-old children, with no notable variations in 7–9-year-old children. Conclusion: This study emphasizes the importance of precise nutrition, particularly protein and essential AA, crucial for children’s health. Addressing undernutrition is crucial, and highlighting the urgency of this concern.

A Clinical Study of Urine Amino Acids in Children with Autism Spectrum Disorder.

We designed a case-control study that consisted of 75 boys and girls, aged between 2 and 12 years. For amino acid profile, we used urine samples that were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Descriptive analysis showed higher values for glutamine, hydroxyproline, tyrosine, aspartic acid, and tryptophan and lower values for serine in the autism group than in the control group. Also, we found that boys with autism had higher values than the boys in the control group for serine, threonine, and aspartic acid. For girls from both groups, we did not find statistically significant values. In terms of age groups, we found significantly higher values for histidine, threonine, valine, methionine, aspartic acid, glutamic acid, alpha amino-adipic acid, sarcosine, alanine, and beta-alanine and significantly lower values for proline for both the autism and control groups under 5 years. The findings of this study support the assumption that amino acids may have a role in the expression of ASD.

Comparative Analysis of Amino Acid Profile of Tenualosa Ilisha and Catla Catla and Their Potential Contribution to Recommended Nutrient Intake

Objective: The current study aimed to determine the amino acid profiles and proximate compositions of two commonly consumed fish species of Bangladesh: Tenualosa ilisha and Catla catla, commonly known as Hilsha, the national fish of Bangladesh and Catla, respectively. Methodology: The fish samples were collected from two wholesale fish markets (ghaats) in Dhaka city, the capital of Bangladesh. The Amino Acid content of the selected samples was analyzed by an amino acid analyzer. Fourteen amino acids (eight essential and six non-essential) could be detected by the analyzer. Results: In the case of the essential amino acid content of the samples, threonine, valine, isoleucine, histidine, and lysine content was greater in the Hilsha fish than that of Catla. On the other hand, methionine, leucine, and phenylalanine content were higher in Catla than that in Hilsha. All six non-essential amino acids were found in greater amounts in Hilsha. Concerning the potential contribution (%) of the selected samples to the daily recommended nutrient intake (RNI) of essential amino acids in children (5-10 years), Hilsha fish potentially contributes (>50%) to the daily RNI of threonine, methionine, and lysine and Catla fish potentially contributes (>50%) to the daily RNI of methionine and lysine. In regards to the adult’s RNI, Hilsha potentially contributes (>50%) to the daily RNI of methionine and lysine but Catla was found to contribute potentially (>50%) to the daily RNI of methionine only. Conclusion: Both of the samples were found to be a substantial source of protein and essential amino acids to significantly contribute to the daily RNI of essential amino acids concerning children (5-10 years) for growth and adults for maintenance. Bioresearch Commu. 10(1): 1371-1377, 2024 (January)

Catabolism of fats and branched-chain amino acids in children with Type 1 diabetes: Association with glycaemic control and total daily insulin dose.

Hyperglycaemia in Type 1 diabetes (T1D) results from an absolute insulin deficiency. However, insulin resistance (IR) may exacerbate glycaemic instability in T1D and contribute to long-term cardiovascular complications. We previously showed that IR in teenagers with obesity is associated with sex-dependent derangements in the catabolism of branched-chain amino acids (BCAA) and fatty acids. Here we hypothesized that byproducts of BCAA and fatty acid metabolism may serve as biomarkers or determinants of glycaemic control and IR in prepubertal or early pubertal children with T1D. Metabolites, hormones and cytokines from fasting blood samples were analysed in 28 children (15 females, 13 males; age 6-11 years) with T1D. Principal components analysis (PCA) and multiple linear regression models were used to correlate metabolites of interest with glycaemic control, total daily insulin dose (TDD, units/kg/d), adiponectin and the triglyceride (TG) to high-density lipoprotein (HDL) ratio. Males and females were comparable in age, BMI-z, insulin sensitivity, glycaemic control, inflammatory markers, BCAAs and C2/C3/C5-acylcarnitines. The majority of components retained in PCA were related to fatty acid oxidation (FAO) and BCAA catabolism. HbA1c correlated positively with Factor 2 (acylcarnitines, incomplete FAO) and Factor 9 (fasting glucose). TDD correlated negatively with C3 and C5 and Factor 10 (BCAA catabolism) and positively with the ratio of C2 to C3 + C5 and Factor 9 (fasting glucose). These findings suggest that glucose intolerance in prepubertal or early pubertal children with T1D is accompanied by incomplete FAO while TDD is associated with preferential catabolism of fats relative to amino acids.

Evaluation of Branched-Chain Amino Acids in Children with Autism Spectrum Disorder and Epilepsy.

Autism spectrum disorder (ASD) and epilepsy run hand-to-hand in their pathophysiology. Epilepsy is not an uncommon finding in patients with ASD. The aim of the present study was to identify the metabolic abnormalities of BCAAs (leucine, isoleucine, and valine) in children with ASD with and without seizures in comparison with neurotypical controls. Also, this study aimed to investigate the presence of epileptiform discharges on electroencephalography (EEG) in ASD patients and to describe the types and frequency of seizures observed. The study included 90 children aged 2-7years, 30 of whom were diagnosed with both ASD and epilepsy. The other 30 children were diagnosed as ASD without epilepsy, and a comparable 30 normally developed children served as a control group. The groups were matched by age and gender. All patients were referred to the Autism Disorders Clinic for interviews and examinations. The Childhood Autism Rating Scale (CARS) was applied to all study participants to assess the degree of autism. The present study results show that all types of seizures may be identified in ASD children. The median serum levels of BCAAs were lower in ASD children with and without epilepsy than in neurotypical controls. This opens the door for discussion about new etiologies and better categorizations of ASD based on genotype and genetic abnormalities detected. More studies with larger samples are needed to understand ASD better and to more reliable evaluate the association between ASD, EEG changes, seizures, and BCAAs.

Derangement of Arginine and Related Amino Acids in Children Undergoing Surgery for Congenital Heart Disease With Cardiopulmonary Bypass.

Prospective observational study. The study was conducted in the Heart Center at Texas Children's Hospital. Children undergoing surgery for congenital heart disease with cardiopulmonary bypass. None. Serial perioperative blood samples were collected for quantification of amino acids, arginase, nitric oxide metabolites, and markers of organ function (lactate, Pao2/Fio2 ratio, and creatinine clearance). Thirty children (18 males) were included in the study; median (interquartile range) age 0.5 years (0.3-0.9 yr). The mean ± sd for plasma amino acid concentrations before cardiopulmonary bypass: arginine 62 ± 20 µmol/L, citrulline 24 ± 6 µmol/L, ornithine 53 ± 32 µmol/L, and glutamine 591 ± 126 µmol/L. Arginine concentration was decreased within the first 24 hours (43 ± 15 µmol/L; p = 0.004), citrulline and glutamine concentrations decreased over the first 48 hours (11 ± 4 µmol/L; p < 0.001 and 493 ± 131 µmol/L; p = 0.019, respectively) and were associated with an increase in arginase (3.8 ± 3 µg/mL; p < 0.05). There was an increase in Vasoactive-Inotropic Score (5.9 ± 19 vs 0.5 ± 2; p < 0.001), decrease in creatinine clearance (76 ± 24 vs 93 ± 31; p = 0.002), and Pao2/Fio2 ratio (243 ± 138 vs 374 ± 200; p = 0.007) comparing to baseline. A widely variable degree of arginine, citrulline, and glutamine depletion occurs in children after surgery for congenital heart disease. These findings were associated with increased arginase and coincide with some of the markers of organ perfusion.

Urinary Excretion of Amino Acids in Children with Type 1 Diabetes

Urinary Excretion of Amino Acids in Children with Type 1 Diabetes

Altered Urinary Amino Acids in Children With Autism Spectrum Disorders

Autism spectrum disorders (ASD) affect 1% of children. Although there is no cure, early diagnosis and behavioral intervention can relieve the symptoms. The clinical heterogeneity of ASD has created a need for improved sensitive and specific laboratory diagnostic methods. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based analysis of the metabolome has shown great potential to uncover biomarkers for complex diseases such as ASD. Here, we used a two-step discovery–validation approach to identify potential novel metabolic biomarkers for ASD. Urine samples from 57 children with ASD and 81 matched children with typical development (TD) were analyzed by LS-MS/MS to assess differences in urinary amino acids and their metabolites (referred to as UAA indicators). A total of 63 UAA indicators were identified, of which 21 were present at significantly different levels in the urine of ASD children compared with TD children. Of these 21, the concentrations of 19 and 10 were higher and lower, respectively, in the urine of ASD children compared with TD children. Using support vector machine modeling and receiver operating characteristic curve analysis, we identified a panel of 7 UAA indicators that discriminated between the samples from ASD and TD children (lysine, 2-aminoisobutyric acid, 5-hydroxytryptamine, proline, aspartate, arginine/ornithine, and 4-hydroxyproline). Among the significantly changed pathways in ASD children were the ornithine/urea cycle (decreased levels of the excitatory amino acid aspartate [p = 2.15 × 10-10] and increased arginine/ornithine [p = 5.21 × 10-9]), tryptophan metabolism (increased levels of inhibitory 5-hydroxytryptamine p = 3.62 × 10-9), the methionine cycle (increased methionine sulfoxide [p = 1.46 × 10-10] and decreased homocysteine [p = 2.73 × 10-7]), and lysine metabolism (reduced lysine [p = 7.8 × 10-9], α-aminoadipic acid [p = 1.16 × 10-9], and 5-aminovaleric acid [p = 1.05 × 10-5]). Collectively, the data presented here identify a possible imbalance between excitatory and inhibitory amino acid metabolism in ASD children. The significantly altered UAA indicators could therefore be potential diagnostic biomarkers for ASD.

Assessment of antioxidant enzymes, total sialic acid, lipid bound sialic acid, vitamins and selected amino acids in children with phenylketonuria.

In this study, children with phenylketonuria and healthy control subjects were assessed for glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT) activity, malondialdehyde (MDA), glutathione (GSH), retinol, cholecalciferol, α-tocopherol, phylloquinone, total sialic acid (TSA), lipid bound sialic acid (LSA), total antioxidant (TAS), total oxidation (TOS), and amino acid levels, and the relationships of these variables with phenylketonuria were evaluated. The study included 60 children with phenylketonuria and 30 control subjects. Children with phenylketonuria were divided into hyperphenylalaninemia (HPA) and amino acid mixture (AAM) groups. The HPA group had significantly lower levels of GSH-Px, CAT, GSH, TAS, α-aminobutyric acid, and taurine levels (p < 0.01, p < 0.05, p < 0.05, p < 0.001, p < 0.01, p < 0.05, respectively) than the control group. Additionally, the AAM group had significantly lower levels of CAT, TAS, and phylloquinones (p < 0.05, p < 0.05, p < 0.05, respectively) than the control group. It was observed in our study that in the HPA group, a significantly strong positive linear correlation was observed between phenylalanine and α-aminoadipic acid (r = 0.777; p = 0.002). It was concluded that the levels of α-aminoadipic acid and phylloquinone might be an appropriate choice for the determination of phenylketonuria in parallel with the levels of phenylalanine. α-aminobutyric acid and phylloquinone as a supplement can decrease HPA damage.

Plasma profile and urine excretion of amino acids in children with celiac disease on gluten-free diet after oligofructose-enriched inulin intervention: results of a randomised placebo-controlled pilot study

The circulating amino acid (AAs) concentrations are indicators of dietary protein intake and metabolic status. In celiac disease (CD), the AA imbalance is frequently observed. Prebiotics are found to alleviate nutrient deficiencies. Therefore, the aim of this study was to analyse the impact of oligrofructose-enriched inulin (Synergy 1), administered for 3 months as a gluten-free diet (GFD) supplement to children with CD, on the plasma and urine concentrations of AAs. CD children (N = 34) were randomised into two groups, receiving Synergy 1 (10 g/day) or placebo (maltodextrin) for 3 months. The AA profile and concentration was determined in plasma and urine before and after the dietary intervention by gas chromatography. 22 and 28 AAs were determined in plasma and urine samples, respectively. After the intervention, the plasma concentrations of several AAs (Ala, Pro, Asn, Glu, Tyr, Lys, His, Orn) increased significantly in both experimental groups, while Gln increased only in the Synergy 1 group. The urinary excretion of Asn, Lys and Aaa increased significantly in the Synergy 1 group, and the excretion of Asp and Met decreased (p < 0.05) in the placebo group. The Gln:Glu ratio in urine increased in both groups after the intervention. An increased urinary excretion of AAs observed in Synergy 1 group with a simultaneous increase in the content of circulating AAs could be attributed to higher absorption or intensified metabolism of AAs, and on the other hand further healing of the intestinal mucosa being the result of continuous treatment with GFD. Moreover, the observed changes in Glu concentration suggest that oligofructose-enriched inulin could improve the intestinal condition and permeability. To conclude, a prebiotic-supplemented GFD influences beneficially the overall AAs metabolism in CD children; however, further prospective cohort studies are needed to confirm the results obtained.

Decreased levels of urinary free amino acids in children with autism spectrum disorder

Autism spectrum disorder (ASD) is a range of neurodevelopmental problems without certain causes. Conventional diagnostic or screening tools for ASD rely on the observation of children’s behavioral presentations. Novel methods are focused on the alterations of some important biochemical matters in ASD patients, which are applicable in the screening for ASD. This study investigated and compared amino acids in the first morning urine from age and sex matched ASD and non-ASD children using high performance liquid chromatography. Significantly lower urinary free methionine, phenylalanine, valine, tryptophan, and leucine plus isoleucine were observed in ASD children. The effects of using urinary free amino acids (UFAAs) singly or conjointly to classify participants into ASD or control group were analyzed and compared. ROC curves on these UFAAs singly in classification performed the sensitivity of 0.593–0.889 and the specificity of 0.704–0.963. Binary-logistic regression analysis of these UFAAs obtained a final regression model comprised of urinary free valine and tryptophan. The ROC curve established by the linear combination of the two amino acids achieved a sensitivity of 0.926 and a specificity of 0.889, which showed superiority to single UFAA and comparability to existing diagnostic or screening tools. It was suggested that the multivariate model based on UFAAs was possibly applicable in screening for children at higher risk of ASD.

Investigating plasma amino acids for differentiating individuals with autism spectrum disorder and typically developing peers

BackgroundPlasma amino acid measurements have been extensively investigated in individuals with autism spectrum disorder (ASD). Results thus far have been inconclusive as studies generally disagree on which amino acids are different in individuals with ASD versus their typically developing (TD) peers, due in part to methodological limitations of several studies. MethodThis paper investigates plasma amino acids in children and adults with ASD using data from Arizona State University’s Comprehensive Nutritional and Dietary Intervention Study. Measurements from 64 individuals with ASD and 49 TD controls were analyzed using univariate and multivariate statistical techniques. ResultsUnivariate analysis indicated increased median levels of glutamate (+21%, p = 0.014) and serine (+8%, p = 0.043), and increased mean levels of hydroxyproline (+17%, p = 0.018) for the ASD cohort, although these differences were insignificant after correcting for multiple comparisons. A multivariate approach was used to classify study participants into ASD/TD cohorts using Fisher discriminant analysis (FDA) and its nonlinear extension, kernel Fisher discriminant analysis (KFDA). Model fitting with FDA using all available measurements produced Type I and Type II errors of 27.0% and 27.8%, respectively. KFDA was most effective when using hydroxyproline, leucine, and threonine as inputs; however, leave-one-out cross-validation with this nonlinear model only resulted in 70.3% sensitivity and 77.6% specificity. ConclusionsThe finding of elevated glutamate in ASD is in agreement with several other studies. Overall, however, these results suggest that plasma amino acid measurements are of limited use for purposes of ASD classification, which may explain some of the inconsistencies in results presented in the literature.

Circulating branched-chain amino acids in children with obstructive sleep apnea

The effects of obstructive sleep apnea (OSA) on the metabolic system are not well understood, especially in children. Recent studies have provided evidence of the modulation of insulin action by branched-chain amino acids (BCAAs) and suggested novel mechanistic relationships between glucose and amino acid metabolic pathways. We hypothesized that plasma BCAA levels may serve as biomarkers of insulin resistance and metabolic dysfunction in children with OSA. A polysomnography was conducted for the diagnosis of OSA in 90 snoring children, in a tertiary hospital. Anthropometric and clinical data were measured and venous blood samples were collected for the measurement of plasma glucose, insulin, HbA1c, and amino acids. Children with OSA had significantly higher levels of BCAAs (leucine, isoleucine, and total BCAAs) compared with those without OSA (P = 0.024). A positive significant correlation was observed between insulin levels and both leucine and isoleucine (r = 0.232; P < 0.05). On multivariate regression analyses, the presence of OSA was significantly associated with leucine, isoleucine, and total BCAA concentrations (P = 0.028), whereas the arousal index was associated with leucine, valine, and total BCAA levels (P = 0.037). The presence of OSA and sleep fragmentation may induce changes in branched-chain amino acid metabolism in snoring children, independently of obesity. These data may suggest a new mechanism linking OSA and glucose homeostasis.

Evaluation of trace element and mineral status and related to levels of amino acid in children with phenylketonuria.

The aim of the present study was to examine trace elements (Zn, Cu, Mn, Se, Fe, Co, Cr, Ni, Cd, Pb), minerals (Ca, Mg, K), amino acids status in children with phenylketonuria and also whether they were correlated with each other in phenylketonuric patients. It has been found out that the HPA group was significantly lower than the control group with regards to Zn, Se, K, Ca, Mg and Zn/Cr levels (p<0.001, p<0.01, p<0.001, p<0.01, p<0.01 and p<0.001 respectively). In the patients with HPA, significantly strong positive correlations were observed between magnesium and calcium (r=0.791; p=0.001), also, indicates negative significant correlation between the concentrations of magnesium and phenylalanine (r=-0.591; p=0.026). The results of this study showed that, in the HPA group, phenylalanine-Mg relationship found, the presence of disease will in the evaluation of phenylalanine and other amino acids, together with the value of magnesium is required to consider.

Choline supplementation alters some amino acid concentrations with no change in homocysteine in children with cystic fibrosis and pancreatic insufficiency

The present study determined the plasma amino acid status in children with cystic fibrosis (CF) and pancreatic insufficiency (PI) in the modern medical and nutritional care setting and investigated the effect of choline supplementation on amino acid status. A total of 110 children aged 5 to 18 years with CF and PI were randomized to receive choline-enriched structured lipid (LYM-X-SORB) or placebo with similar energy and fat content. Plasma amino acids were measured at baseline and 3 and 12 months. We hypothesized that choline supplementation would result in lower plasma homocysteine concentrations in children with CF. At baseline, dietary protein intake was high and the amino acid profile was within laboratory reference ranges in most participants. Alanine and cysteine were elevated in 24% and 36% of participants, respectively. Children with baseline alanine above reference range had improved weight, body mass index, and fat-free mass. Low homocysteine was found in 62% of children 11 years and older. After 3 and 12 months, there was no effect of choline supplementation on methionine or homocysteine status. Compared with placebo, choline supplementation resulted in increased glycine and decreased threonine, histidine, valine, and total branch chained amino acids at 12 months. In conclusion, daily choline supplementation with LYM-X-SORB did not alter methionine-homocysteine metabolism but did result in alterations in other amino acids in children with CF and PI.

Some Amino Acids Levels: Glutamine, Glutamate, and Homocysteine, in Plasma of Children with Chronic Kidney Disease

Background: The high prevalence of protein-energy malnutrition is a critical issue for patients with chronic kidney disease (CKD). Serum albumin is the most commonly used nutritional marker. Another index is plasma amino acid (AA) profile. Of these, the plasma levels of glutamine, glutamate and homocysteine, correlate well with nutritional status. We measured some plasma AAs in children with different stages CKD to provide information in monitoring the therapeutic strategy, particularly in AA supplementary therapy or protein restriction. Methods: Three amino acids were evaluated along with albumin and high sensitivity C-reactive protein (hs-CRP) in 30 patients with advanced CKD stages 4 and 5. They were divided into two groups undergoing conservative treatment (CT) (n=15) or hemodialysis (HD) (n=15). An additional group of patients with nephrotic syndrome [CKD stage 2] was also studied to assess the alterations of plasma free amino acids with the early stage of CKD. Another 30 age- and sex-matched healthy children served as controls. Results: A significant increase in plasma concentration of amino acid glutamine was observed in children with advanced CKD stages 4 and 5 when compared with controls (P=0.02).Plasma glutamine level was significantly higher in ESRD children on HD than in children with nephrotic syndrome (P=0.02). We did not find a significant difference between HD children and CT children as regard to glutamine level. Notable differences were in the plasma homocysteine level detected in the CKD groups patients, which was greater than that in controls (P=0.0001). Plasma homocysteine level was significantly higher in children on HD than in children with nephrotic syndrome (P=0.01).A significant differences was observed in hs-CRP levels between the CKD groups and the controls (P=0.04).Albumin levels were lower in CKD groups than in controls (p=0.01). Glutamine showed significant positive correlations with blood urea level (r=0.84, P=0.002) and blood ammonia level (r=0.72, P=0.0001). On multiple linear regression, urea was the only variable independently associated with an elevated plasma glutamine level (Beta=0.77, P=0.02). Conclusion: This study indicates that the advanced stages of CKD are associated with increased plasma concentrations of glutamine and homocysteine. Glutamine retained in the plasma of children with CRF, possibly producing higher levels of the waste products (urea and NH3). Dialysis alone is insufficient to redress completely the abnormalities in AA metabolism in ESRD children. Careful consideration of dialysis and dietary measures are necessary.

CSF/plasma ratios of amino acids: Reference data and transports in children

Objective: We intended to investigate the effects of age, gender, and medications on amino acid cerebrospinal fluid (CSF)/plasma ratios in children, and to determine whether amino acid transports across the blood–CSF barrier in children differ from those in adults. Patients and methods: Amino acid concentrations measured by ion-exchange high-performance liquid chromatography were used (CSF from 99 children, simultaneously collected plasma from 76 children). Influence of age, gender, and medications on the amino acid CSF concentrations and CSF/plasma ratios were analyzed by linear multiple regression. Interactions of amino acid transports were analyzed by correlation analysis of CSF/plasma ratios. Results: CSF/plasma ratios of serine, valine, histidine, and arginine were higher in younger children. The glutamate CSF/plasma ratio was higher in older children. Serine, alanine, threonine, valine, and histidine CSF/plasma ratios were lower in females. Glutamine, methionine, tyrosine, and phenylalanine CSF/plasma ratios were elevated with valproate therapy. Serine, threonine, valine, leucine, and tyrosine CSF/plasma ratios were lower with clobazam therapy. The asparagine CSF/plasma ratio was elevated with pyridoxal phosphate therapy. Transports of most essential neutral amino acids interacted with each other, as did neutral amino acids with low molecular weights. Cationic amino acids interacted with each other and some essential neutral amino acids. Acidic amino acids had no interactions with other amino acids. Conclusions: Age, gender, and anti-epileptic drugs affect amino acid CSF/plasma ratios in children. Transport interactions between amino acids in children showed no remarkable difference from those of adults and generally followed the substrate specificities of multiple amino acid transport systems.

Evidence That Phenylalanine May Not Provide the Full Needs for Aromatic Amino Acids in Children

Phenylalanine is nutritionally classified as an indispensable amino acid and can be converted to tyrosine by phenylalanine hydroxylation. The initial goal of the present study was to determine the aromatic amino acid (phenylalanine plus tyrosine) requirements in healthy children fed a diet without tyrosine by using the indicator amino acid oxidation (IAAO) method using lysine as the indicator amino acid. Healthy school-age children (n = 5) were fed in random order a diet with eight graded intakes of phenylalanine without tyrosine. The requirement was determined by the rate of recovery of CO2 from L-[1-C]lysine oxidation (FCO2). Phenylalanine (total aromatic amino acid) requirement, in the absence of tyrosine, for children was determined to be 28 mg/kg/d, which was only 64% of the adult requirement, which is biologically absurd. A possible reason for the lower estimate of phenylalanine requirement could be lower phenylalanine hydroxylation rate in children, which is supported by the finding of lower urinary tyrosine/phenylalanine ratios in children compared with adults. In conclusion, this study indicates that phenylalanine may not provide the total needs for aromatic amino acids in children fed an amino acid-based diet without tyrosine.

Nitrogen and Amino Acid Requirements: The Massachusetts Institute of Technology Amino Acid Requirement Pattern

We review the current international recommendations concerning the protein (nitrogen) and amino acid requirements of healthy individuals, from infancy to the later years of adult life and describe the changes in the recommendations for protein that have been made, since those issued in 1985 by Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU), by the International Dietary Energy Consultative Group. The current international requirements for the specific indispensable amino acids are critiqued briefly, and the rationale and basis for the proposed Massachusetts Institute of Technology (MIT) amino acid requirement pattern are presented. The evidence is then summarized that supports its use in practical considerations of protein nutrition. It is suggested that this MIT amino acid requirement pattern provides the best current estimates of the minimum physiological requirements for the indispensable amino acids in children and adults. It is further concluded that it would be difficult to argue for the continued use of the amino acid requirement values proposed by FAO/WHO/UNU in 1985 in the planning and assessment of dietary protein intakes for population groups worldwide. The MIT amino acid requirement pattern supports and strengthens the relevance of dietary protein quality as an important factor in human protein and amino acid nutrition.

Value of Intraperitoneal Amino Acids in Children Treated with Chronic Peritoneal Dialysis

Value of Intraperitoneal Amino Acids in Children Treated with Chronic Peritoneal Dialysis