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Millward DJ. Post-prandial tracer studies of protein and amino acid utilisation: what can they tell us about human amino acid and protein requirements? Br J Nutr 2024; 131:2005-2030. [PMID: 38606599 PMCID: PMC11361918 DOI: 10.1017/s0007114524000734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 02/26/2024] [Accepted: 03/13/2024] [Indexed: 04/13/2024]
Abstract
Nitrogen balance (NB), the principal methodology used to derive recommendations for human protein and amino acid requirements, has been widely criticised, and calls for increased protein and amino acid requirement recommendations have been made, often on the basis of post-prandial amino acid tracer kinetic studies of muscle protein synthesis, or of amino acid oxidation. This narrative review considers our knowledge of the homeostatic regulation of the FFM throughout the diurnal cycle of feeding and fasting and what can and has been learnt from post-prandial amino acid tracer studies, about amino acid and protein requirements. Within the FFM, muscle mass in well fed weight-stable adults with healthy lifestyles appears fixed at a phenotypic level within a wide range of habitual protein intakes. However homoeostatic regulation occurs in response to variation in habitual protein intake, with adaptive changes in amino acid oxidation which influence the magnitude of diurnal losses and gains of body protein. Post-prandial indicator amino acid oxidation (IAAO) studies have been introduced as an alternative to NB and to the logistically complex 24 h [13C-1] amino acid balance studies, for assessment of protein and amino acid requirements. However, a detailed examination of IAAO studies shows both a lack of concern for homeostatic regulation of amino acid oxidation and major flaws in their design and analytical interpretation, which seriously constrain their ability to provide reliable values. New ideas and a much more critical approach to existing work is needed if real progress is to be made in the area.
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Affiliation(s)
- D. Joe Millward
- Department of Nutritional Sciences, School of Biosciences & Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
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Szwiega S, Pencharz PB, Ball RO, Xu L, Kong D, Elango R, Courtney-Martin G. Length of Adaptation Has No Effect on the Threonine Requirement Determined in Healthy Young Adult Males Using the Indicator Amino Acid Oxidation Method. J Nutr 2023; 153:2016-2026. [PMID: 37004875 DOI: 10.1016/j.tjnut.2023.03.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 03/21/2023] [Accepted: 03/28/2023] [Indexed: 04/03/2023] Open
Abstract
BACKGROUND The indicator amino acid oxidation (IAAO) method is minimally invasive; therefore, it is applicable to study the amino acid (AA) requirements of individuals in various age groups. However, the accuracy of this method has been criticized because of the 8 h (1 d) protocol, which has been suggested to be too short an adaptation time for estimating AA requirements. OBJECTIVES The IAAO method was used to determine whether 3 or 7 d of adaptation to each threonine intake alters the threonine requirement in adult men compared to 1 d of adaptation. METHODS Eleven healthy adult men (19-35 y, body mass index (BMI) 23.4 in kg⋅m-2) were studied at 6 threonine intakes; each intake was studied over a 9 d period. Following 2 d of pre-adaptation to adequate protein intake (1.0 g·kg-1⋅d-1), subjects received experimental diets containing the randomly assigned test threonine intake (5, 10, 15, 20, 25, or 35 mg·kg-1·d-1) for 7 d. IAAO studies were performed on days 1, 3, and 7 of adaptation to the experimental diet. The rate of release of 13CO2 from the oxidation of L-[1-13C]phenylalanine (F13CO2) was measured, and the threonine requirement was determined by applying mixed-effect change-point regression to the F13CO2 data in R version 4.0.5. The 95% confidence interval (CI) was calculated using parametric bootstrap, and the requirement estimates on days 1, 3, and 7 were compared using analysis of variance (ANOVA). RESULTS The mean threonine requirements (upper, lower 95% CI) for days 1, 3, and 7 were 10.5 (5.7, 15.9), 10.6 (7.5, 13.7), and 12.1 (9.2, 15.0 mg·kg-1·d-1), respectively; and these requirements were not statistically different (P = 0.213). CONCLUSIONS We demonstrated that the short, 8 h IAAO protocol results in a threonine requirement that is not statistically different from that obtained on days 3 or 7 of adaptation in healthy adult males. This trial was registered at www. CLINICALTRIALS gov as NCT04585087.
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Affiliation(s)
- Sylwia Szwiega
- Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Paul B Pencharz
- Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada; Departments of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada; Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada
| | - Ronald O Ball
- Department of Agriculture, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | - Libai Xu
- Department of Statistical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Dehan Kong
- Department of Statistical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Rajavel Elango
- Department of Pediatrics, School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada; British Columbia Children's Hospital Research Institute, British Columbia Children's Hospital, Vancouver, British Columbia, Canada
| | - Glenda Courtney-Martin
- Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada; Departments of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada; Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada.
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Szwiega S, Pencharz PB, Ball RO, Tomlinson C, Elango R, Courtney-Martin G. Amino acid oxidation methods to determine amino acid requirements: do we require lengthy adaptation periods? Br J Nutr 2023; 129:1848-1854. [PMID: 36045125 PMCID: PMC10167660 DOI: 10.1017/s0007114522002720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 08/03/2022] [Accepted: 08/18/2022] [Indexed: 11/05/2022]
Abstract
Determination of indispensable amino acid (IAA) requirements necessitates a range of intakes of the test IAA and monitoring of the physiological response. Short-term methods are the most feasible for studying multiple intake levels in the same individual. Carbon oxidation methods measure the excretion of 13CO2 in breath from a labelled amino acid (AA) in response to varying intakes of the test AA following a period of adaptation. However, the length of adaptation to each AA intake level has been a source of debate and disagreement among researchers. The assertion of the minimally invasive indicator amino acid oxidation (IAAO) technique is that IAA requirements can be estimated after only a few hours (8 h) of adaptation to each test AA intake, suggesting that adaptation occurs rapidly in response to dietary adjustments. On the contrary, the assertion of most other techniques is that 6-7 d of adaptation is required when determining IAA needs. It has even been argued that a minimum of two weeks is needed to achieve complete adaptation. This review explores evidence regarding AA oxidation methods and whether long periods of adaptation to test IAA levels are necessary when estimating IAA requirements. It was found that the consumption of experimental diets containing lower test IAA intake for greater than 7 d violates the terms of a successful adaptive response. While there is some evidence that short-term 8 h IAAO is not different among different test amino acid intakes up to 7 d, it is unclear whether it impacts assessment of IAA requirements.
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Affiliation(s)
- Sylwia Szwiega
- Research Institute, Hospital for Sick Children, Toronto, ONM5G 1X8, Canada
| | - Paul B. Pencharz
- Research Institute, Hospital for Sick Children, Toronto, ONM5G 1X8, Canada
- Departments of Nutritional Sciences, University of Toronto, Toronto, M5S 2Z9ON, Canada
- Departments of Paediatrics, University of Toronto, Toronto, M5S 2Z9ON, Canada
| | - Ronald O. Ball
- Department of Agriculture, Food and Nutritional Science, University of Alberta, Edmonton, T6G 2P5AL, Canada
| | - Christopher Tomlinson
- Research Institute, Hospital for Sick Children, Toronto, ONM5G 1X8, Canada
- Departments of Nutritional Sciences, University of Toronto, Toronto, M5S 2Z9ON, Canada
| | - Rajavel Elango
- Department of Pediatrics, School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada
- BC Children’s Hospital Research Institute, BC Children’s Hospital, Vancouver, V5Z 4H4BC, Canada
| | - Glenda Courtney-Martin
- Research Institute, Hospital for Sick Children, Toronto, ONM5G 1X8, Canada
- Departments of Nutritional Sciences, University of Toronto, Toronto, M5S 2Z9ON, Canada
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ONM5S 2Z9, Canada
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Szwiega S, Pencharz PB, Courtney-Martin G. Reply to DJ Millward. Am J Clin Nutr 2021; 113:1055-1056. [PMID: 33822864 DOI: 10.1093/ajcn/nqab032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Sylwia Szwiega
- From the Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Paul B Pencharz
- Departments of Nutritional Sciences, Medican Science Building, 1 King's College Circle, Toronto, ON, Canada
- Paediatrics, 555 University Ave, Black Wing, Toronto, ON, Canada
| | - Glenda Courtney-Martin
- Departments of Nutritional Sciences, Medican Science Building, 1 King's College Circle, Toronto, ON, Canada
- Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada
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Jiang Z, Lin C, Liu H, Feng J, Zheng Z, Cai S. Specific biological responses following dextran-coated ultra-small superparamagnetic particles of iron oxides administration. Nanomedicine (Lond) 2019; 14:1371-1386. [PMID: 31215328 DOI: 10.2217/nnm-2018-0433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aim: The potential bio-related risks of dextran-coated ultra-small superparamagnetic particles of iron oxides (D-USPIO) were assessed. Materials & methods: Metabolic responses of D-USPIO in BALB/C mice were obtained using 1H-NMR-based metabolomic strategy combined with the traditional biochemical assay. Results: The metabolomic analyses of biological fluids (plasma and urine) and organs (liver, kidney and spleen) indicated that the disturbance, impairment and recovery of the physiological functions were related to the metabolic response to D-USPIO. The correlations between the biofluids and tissue metabolomes described the specific metabolic information of D-USPIO on their in vivo transportation, absorption, biodistribution and excretion. Conclusion: Metabolomic analysis provides preliminary validation for the use of D-USPIO in clinical medicine, and the results help to understand the potential adverse effects of the similar bio-nanomaterials further serve to their synthesis optimization and biocompatibility improvement.
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Affiliation(s)
- Zhiming Jiang
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma & Magnetic Resonance, Xiamen University, Xiamen 361005, PR China
| | - Chenghong Lin
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma & Magnetic Resonance, Xiamen University, Xiamen 361005, PR China
| | - Huili Liu
- State Key Laboratory of Magnetic Resonance & Atomic & Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics & Mathematics, Chinese Academy of Sciences, Wuhan 430071, PR China
| | - Jianghua Feng
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma & Magnetic Resonance, Xiamen University, Xiamen 361005, PR China
| | - Zhenyao Zheng
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma & Magnetic Resonance, Xiamen University, Xiamen 361005, PR China
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma & Magnetic Resonance, Xiamen University, Xiamen 361005, PR China
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Shivakumar N, Minocha S, Kurpad AV. Protein quality & amino acid requirements in relation to needs in India. Indian J Med Res 2018; 148:557-568. [PMID: 30666983 PMCID: PMC6366268 DOI: 10.4103/ijmr.ijmr_1688_18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Indexed: 11/04/2022] Open
Abstract
The relevance of protein and its constituent amino acids (AAs) in the structure and function of the human body is well known. Accumulating evidence has conferred specific functional and regulatory roles for individual AAs, adding relevance to their requirements across different age groups. The methods for measuring AA requirements have progressed from the classical nitrogen balance to the current stable isotope-based AA balance methods. Requirements of most of the indispensable AA (IAA) have been estimated in healthy Indian population by the best available balance method and has shown to be higher than earlier 1985 WHO/FAO/UNU (World Health Organization/Food and Agriculture Organization/United Nations University) recommendations. In addition, potential changes in the requirement, through adaptation to chronic undernutrition or to infection, have also been evaluated. In 2007, the WHO/FAO/UNU released a recommendation that increased the daily IAA requirement, based on primary evidence from Indian balance studies. This meant that to ensure that the new IAA requirements were met, individual foods or mixed diets needed to be assessed for their protein quality, or their ability to deliver the required amount of IAA. The recent FAO report on protein quality evaluation recommends the use of a new chemical AA score, the digestible IAA score (DIAAS), to replace the earlier protein digestibility corrected AA score. The DIAAS requires the determination of individual AA digestibility at the ileal level. A minimally invasive dual stable isotope tracer-based approach has been developed in India and has been used to determine digestibility of various foods in Indian adults and children. The increase in IAA requirements and subsequent protein quality requirements have implications for national regulatory frameworks, growth and development, and in turn, for economic and agricultural policy.
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Affiliation(s)
| | - Sumedha Minocha
- Division of Nutrition, St. John's Research Institute, Bengaluru, India
| | - Anura V. Kurpad
- Department of Physiology, St. John's Medical College, Bengaluru, India
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Berryman CE, Lieberman HR, Fulgoni VL, Pasiakos SM. Protein intake trends and conformity with the Dietary Reference Intakes in the United States: analysis of the National Health and Nutrition Examination Survey, 2001-2014. Am J Clin Nutr 2018; 108:405-413. [PMID: 29931213 DOI: 10.1093/ajcn/nqy088] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 04/04/2018] [Indexed: 11/12/2022] Open
Abstract
Background Systematic analysis of dietary protein intake may identify demographic groups within the American population that are not meeting the Dietary Reference Intakes (DRIs). Objective This cross-sectional study analyzed protein intake trends (2001-2014) and evaluated recent conformity to the DRIs (2011-2014) according to age, sex, and race or ethnicity in the US population. Design Protein intakes and trends during 2-y cycles of NHANES 2001-2014 (n = 57,980; ≥2 y old) were calculated as absolute (grams per day) and relative [grams per kilogram of ideal body weight (IBW) per day] intakes and as a percentage of total energy. Sex and race or ethnicity [Asian, Hispanic, non-Hispanic black (NHB), and non-Hispanic white (NHW)] differences were determined for protein intake and percentage of the population below the Estimated Average Requirement (EAR) and Recommended Dietary Allowance, and above and below the Acceptable Macronutrient Distribution Range (AMDR). Results Usual protein intakes (mean ± SE) averaged from 55.3 ± 0.9 (children aged 2-3 y) to 88.2 ± 1.1 g/d (adults aged 19-30 y). Protein comprised 14-16% of total energy intakes. Relative protein intakes averaged from 1.10 ± 0.01 (adults aged ≥71 y) to 3.63 ± 0.07 g · kg IBW-1 · d-1 (children aged 2-3 y), and were above the EAR in all demographic groups. Asian and Hispanic populations aged >19 y consumed more relative protein (1.32 ± 0.02 and 1.32 ± 0.02 g · kg IBW-1 · d-1, respectively) than did NHB and NHW (1.18 ± 0.01 g · kg IBW-1 · d-1). Relative protein intakes did not differ by race or ethnicity in the 2-18 y population. Adolescent (aged 14-18 y) females and older (aged ≥71 y) NHB men had the largest population percentages below the EAR (11% and 13%, respectively); <1% of any demographic group had intakes above the AMDR. Conclusions The majority of the US population exceeds minimum recommendations for protein intake. Protein intake remains well below the upper end of the AMDR, indicating that protein intake, as a percentage of energy intake, is not excessive in the American diet. This trial was registered at www.isrctn.com as ISRCTN76534484.
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Affiliation(s)
- Claire E Berryman
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA.,Oak Ridge Institute for Science and Education, Belcamp, MD
| | - Harris R Lieberman
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA
| | | | - Stefan M Pasiakos
- Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA
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Abstract
The factorial approach is used to measure the dietary indispensable amino acid (IAA) requirements in children, although recent measurements based on the indicator amino acid oxidation (IAAO) method have begun to generate more direct evidence. Difficulties with the factorial method are that it depends on accurate estimates of the maintenance protein requirement, as well as of protein deposition during growth. Also, a value for the efficiency of utilizing dietary protein for deposition has to be selected, based on published Nitrogen (N) balance studies. In the recent 2007 WHO/FAO/UNU report, the amino acid requirement pattern for infants was taken to be similar to the amino acid composition of breast milk. For pre-school and older children, the factorial method gave values for the scoring pattern of protein that were fairly close to the earlier 1985 WHO/FAO/UNU report for children, since growth progressively became a smaller component of the factorial calculation as age progressed. However, given that there are several assumptions in the derivation of factorial estimates, direct experimental measurements of the amino acid requirement are desirable. The IAAO method, as it is non-invasive, as made it possible to measure the IAA requirements in children. Over the last decade, some of the IAA requirements have been determined by using the IAAO method in healthy school age children; however, the data on IAA requirements in developing country populations are still being conducted. In the elderly, there are not enough data to make a separate recommendation for IAA requirements from that of adults.
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Abstract
During the past 25 years a significant amount of research has been conducted to determine amino acid requirements in humans. This is primarily due to advancements in the application of stable isotopes to examine amino acid requirements. The indicator amino acid oxidation (IAAO) method has emerged as a robust and minimally invasive technique to identify requirements. The IAAO method is based on the concept that when one indispensable dietary amino acid (IDAA) is deficient for protein synthesis, then the excess of all other IDAA, including the indicator amino acid, will be oxidized. With increasing intakes of the limiting amino acid, IAAO will decrease, reflecting increasing incorporation into protein. Once the requirement for the limiting amino acid is met there will be no further change in the indicator oxidation. The IAAO method has been systematically applied to determine most IDAA requirements in adults. The estimates are comparable to the values obtained using the more elaborate 24h-indicator amino acid oxidation and balance (24h-IAAO/IAAB) model. Due to its non-invasive nature the IAAO method has also been used to determine requirements for amino acids in neonates, children and in disease. The IAAO model has recently been applied to determine total protein requirements in humans. The IAAO method is rapid, reliable and has been used to determine amino acid requirements in different species, across the life cycle and in disease. The recent application of IAAO to determine protein requirements in humans is novel and has significant implications for dietary protein intake recommendations globally.
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Millward DJ, Jackson AA. Protein requirements and the indicator amino acid oxidation method. Am J Clin Nutr 2012; 95:1498-501; author reply 1501-2. [PMID: 22611079 DOI: 10.3945/ajcn.112.036830] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Elango R, Humayun MA, Ball RO, Pencharz PB. Protein requirement of healthy school-age children determined by the indicator amino acid oxidation method. Am J Clin Nutr 2011; 94:1545-52. [PMID: 22049165 DOI: 10.3945/ajcn.111.012815] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The current Dietary Reference Intake (DRI) recommendations for protein requirements in children are based on a factorial estimate and have not been directly determined. OBJECTIVE The objective of the current study was to determine the protein requirement in healthy, school-age children by measuring the oxidation of L-[1-(13)C]-phenylalanine to (13)CO(2) [label tracer oxidation (F(13)CO(2))] in response to graded intakes of protein. DESIGN Seven healthy children (6-11 y old) each randomly received a minimum of 7 protein intakes (range: 0.1-2.56 g · kg(-1) · d(-1)) for a total of 56 studies. The diets provided energy at 1.7 times the resting energy expenditure and were made isocaloric by using carbohydrate. Protein was given as an amino acid mixture on the basis of the egg-protein pattern, except for phenylalanine and tyrosine intakes, which were maintained constant across intakes. The mean protein requirement was determined by applying a 2-phase linear regression crossover analysis on F(13)CO(2) data, which identified a breakpoint (requirement) at minimal F(13)CO(2) in response to graded amounts of protein intake. RESULTS Mean and population-safe (upper 95% CI) protein requirements were determined to be 1.3 and 1.55 g · kg(-1) · d(-1), respectively. These results are significantly higher than the mean and population-safe protein requirements currently recommended by the DRI 2005 for macronutrients (0.76 and 0.95 g · kg(-1) · d(-1), respectively). CONCLUSION To our knowledge, this study was the first to directly estimate protein requirements in children by using stable isotopes and indicated that current recommendations are severely underestimated.
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Affiliation(s)
- Rajavel Elango
- Research Institute, The Hospital for Sick Children, Toronto, Canada
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Hayamizu K, Kato M, Hattori S. Determining amino acid requirements from repeated observations on indicator amino acid oxidation method by mixed-effect change-point regression models. J Clin Biochem Nutr 2011; 49:115-20. [PMID: 21980227 PMCID: PMC3171677 DOI: 10.3164/jcbn.10-146] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 01/05/2011] [Indexed: 11/26/2022] Open
Abstract
In nutrition studies, it is often of primary interest to determine the critical threshold value of some biological quantities. To determine the amino acid requirement, the tracer approach including the indicator amino acid oxidation method is useful for the investigation of human subjects. In this approach, measurements of amino acids other than the test amino acid are often repeatedly carried out with various intakes of the test amino acid. Change-point regression models have often been applied to determine the amino acid requirement. However, within-subject dependence due to repeated measurements has not been sufficiently taken into account. In this paper, we propose a mixed-effect change-point model to estimate the amino acid requirements when utilizing the tracer approach. Inference based on Akaike Information Criteria is introduced to include selection of the optimal model and construction of a confidence interval. Our method can easily be applied with a standard software package, and we found that appropriate accounting for within-subject dependence may lead to a much narrower confidence interval. We recommend application of a mixed-effect change-point regression model to determine the amino acid requirements in studies utilizing the tracer approach.
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Affiliation(s)
- Kohsuke Hayamizu
- Human Life Science R & D Center, Nippon Suisan Kaisha Ltd., 2-6-2 Otemachi, Chiyoda-ku, Tokyo 100-8686, Japan
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Elango R, Humayun MA, Ball RO, Pencharz PB. Evidence that protein requirements have been significantly underestimated. Curr Opin Clin Nutr Metab Care 2010; 13:52-7. [PMID: 19841581 DOI: 10.1097/mco.0b013e328332f9b7] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW This review discusses recent evidence that suggests a significant underestimation of protein requirements in adult humans. RECENT FINDINGS Traditionally, total protein requirements for humans have been determined using nitrogen balance. The recent Dietary Reference Intake recommendations for mean and population-safe intakes of 0.66 and 0.8 g/kg/day, respectively, of high-quality protein in adult humans are based on a meta-analysis of nitrogen balance studies using single linear regression analysis. We reanalyzed existing nitrogen balance studies using two-phase linear regression analysis and obtained mean and safe protein requirements of 0.91 and 0.99 g/kg/day, respectively. The two-phase linear regression analysis is considered more appropriate for biological analysis of dose-response curves. Considering the inherent problems associated with the nitrogen balance method, we developed an alternative method, the indicator amino acid oxidation technique, to determine protein requirements The mean and population-safe requirements in adult men were determined to be 0.93 and 1.2 g/kg/day and are 41 and 50%, respectively, higher than the current Dietary Reference Intakes recommendations. SUMMARY The indicator amino acid oxidation-based requirement values of 0.93 and 1.2 g protein/kg/day and the reanalysis of existing nitrogen balance studies are significantly higher than current recommendations. Therefore, there is an urgent need to reassess recommendations for protein intake in adult humans.
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Affiliation(s)
- Rajavel Elango
- The Research Institute, The Hospital for Sick Children, Toronto, Canada
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Pillai RR, Elango R, Muthayya S, Ball RO, Kurpad AV, Pencharz PB. Lysine requirement of healthy, school-aged Indian children determined by the indicator amino acid oxidation technique. J Nutr 2010; 140:54-9. [PMID: 19923398 DOI: 10.3945/jn.109.113357] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We recently reported the lysine requirement of school-aged children living in Canada consuming a mixed diet to be 35 mg.kg(-1).d(-1). Because the majority of children in the world live on cereal-based diets in developing countries, we measured the daily lysine requirement in healthy children living in India and consuming a mostly cereal-based diet. Our objective in this study was to determine the lysine requirement in healthy, school-aged children in the developing world by using the indicator amino acid oxidation method with l-[1-(13)C] phenylalanine. Six healthy, school-aged children consumed 7 levels of lysine (5, 15, 25, 35, 50, 65, and 80 mg.kg(-1).d(-1)) each in a random order along with an amino acid mixture providing energy and protein intakes of 1.7 x resting energy expenditure and 1.5 g.kg(-1).d(-1), respectively. The mean lysine requirement was determined by applying a 2-phase linear regression crossover analysis on tracer oxidation (F(13)CO(2)) data, which identified a breakpoint (requirement) at minimal F(13)CO(2) in response to the graded lysine intakes. The mean lysine requirements with the upper 95% CI for children were determined to be 33.5 and 46.6 mg.kg(-1).d(-1), respectively, by breakpoint analysis of the F(13)CO(2) data. The mean lysine requirements of Indian children were almost identical to that of Canadian children (35 mg.kg(-1).d(-1)). There is no evidence for any adaptation in lysine requirements in children from developing countries such as India.
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Affiliation(s)
- Raja R Pillai
- Division of Nutrition, St. John's Research Institute, St. John's National Academy of Health Sciences, Bangalore 560034, India
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Elango R, Humayun MA, Ball RO, Pencharz PB. Indicator amino acid oxidation is not affected by period of adaptation to a wide range of lysine intake in healthy young men. J Nutr 2009; 139:1082-7. [PMID: 19369367 DOI: 10.3945/jn.108.101147] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The number of days of adaptation to a specific amino acid intake required prior to the determination of amino acid requirements using the indicator amino acid oxidation method (IAAO) is still in debate. In this study, our objective was to determine whether adaptation for 8 h, 3 d, and 7 d to a wide range of lysine intakes had any effect on the oxidation of the indicator amino acid, l-[1-(13)C]phenylalanine, to (13)CO(2) (F(13)CO(2)). Five healthy young men randomly received each of 4 levels of lysine (5, 20, 35, and 70 mg x kg(-1) x d(-1)) along with an amino acid mixture to achieve a protein intake of 1.0 g x kg(-1) x d(-1) and energy intake of 1.5x resting energy expenditure during 4 separate 7-d study periods. IAAO studies were conducted on d 1, 3, and 7. During each study day, oral consumption of l-[1-(13)C]phenylalanine was followed by collection of breath for F(13)CO(2) and plasma for measurement of phenylalanine enrichment. F(13)CO(2) was affected by lysine intake but did not differ among adaptation periods of 8 h, 3 d, or 7 d. Phenylalanine flux was not significantly affected by period of adaptation. These results suggest that the minimally invasive IAAO model, where participants are adapted prior to protein intake for 2 d followed by study day adaptation to the test amino acid intake for 8 h, may be sufficient to estimate individual amino acid requirements in healthy young men.
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Affiliation(s)
- Rajavel Elango
- The Research Institute, The Hospital for Sick Children, Toronto M5G 1X8, Canada
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Abstract
PURPOSE OF REVIEW To discuss recent amino acid requirement studies in adult humans and school-age children, primarily determined using the indicator amino acid oxidation technique. RECENT FINDINGS Using the minimally invasive indicator amino acid oxidation model, requirements for most indispensable amino acids have been defined in adult humans. The estimates are comparable to the values obtained using the more elaborate 24-h indicator amino acid oxidation and balance model. The less-invasive indicator amino acid oxidation model has also been successfully applied to define requirements in healthy school-age children and children with disease. A recent adaptation of the indicator amino acid oxidation method to determine protein requirements in adult humans resulted in mean and safe values of 0.93 and 1.2 g protein/kg/day, respectively. These estimates are 40-50% higher than current recommendations and suggest an urgent need to reassess recommendations for protein intake in humans. SUMMARY In summary, indicator amino acid oxidation is a robust technique, and has resulted in the definition of amino acid and protein requirements in adult humans and children. A wider application of the technique in other vulnerable populations across life stages and in other diseases is now possible.
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Affiliation(s)
- Rajavel Elango
- The Research Institute, The Hospital for Sick Children, Toronto, Canada
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Millward DJ. Vernon Young and the development of current knowledge in protein and amino acid nutritionVernon Young 1937–2004. Br J Nutr 2007; 92:189-97. [PMID: 15333147 DOI: 10.1079/bjn20041216] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- D Joe Millward
- Centre for Nutrition and Food Safety, School of Biomedical and Molecular Sciences, University of Surrey, Guildford, GU2 7XH, UK.
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Kurpad AV, Regan MM, Raj TDS, Rao VN, Gnanou J, Young VR. The daily phenylalanine requirement of healthy Indian adults. Am J Clin Nutr 2006; 83:1331-6. [PMID: 16762944 DOI: 10.1093/ajcn/83.6.1331] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The daily requirement for phenylalanine is not known with certainty. Earlier 24-h tracer studies have suggested that the requirement is between 30 and 40 mg . kg(-1) . d(-1). OBJECTIVE The objective was to assess the phenylalanine requirement in healthy well-nourished Indians with the use of 8 test phenylalanine intakes (19, 23, 27, 31, 35, 38, 43, and 47 mg . kg(-1) . d(-1)) and the 24-h indicator amino acid oxidation (24-h IAAO) and 24-h indicator amino acid balance (24-h IAAB) methods. DESIGN Thirty-two healthy, well-nourished Indian men were studied during each of 2 randomly assigned 6-d diet periods in which phenylalanine intakes of 19, 23, 27, 31, 35, 38, 43, and 47 mg . kg(-1) . d(-1) were supplied; the diet was devoid of tyrosine. A 24-h [13C]leucine tracer infusion was used to measure 24-h IAAO and 24-h IAAB on day 7. The breakpoint in the relation between these values and the phenylalanine intake was determined. RESULTS Two-phase linear regression of daily leucine oxidation and balance against phenylalanine intake estimated a breakpoint in the response curve at phenylalanine intakes of 37 and 38 mg . kg(-1) . d(-1) (95% CI for both: 31, >47 mg . kg(-1) . d(-1)), respectively. CONCLUSION On the basis of the 24-h IAAO and 24-h IAAB methods, a mean phenylalanine requirement of 38 mg . kg(-1) . d(-1) is proposed for healthy well-nourished Indian adults in the absence of tyrosine intake. This finding is similar to that in Western adults.
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Affiliation(s)
- Anura V Kurpad
- Institute of Population Health and Clinical Research, St John's National Academy of Health Sciences, Bangalore, India.
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Hsu JWC, Kriengsinyos W, Wykes LJ, Rafii M, Goonewardene LA, Ball RO, Pencharz PB. Leucine is not a good choice as an indicator amino acid for determining amino acid requirements in men. J Nutr 2006; 136:958-64. [PMID: 16549457 DOI: 10.1093/jn/136.4.958] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Leucine tracer has been widely used for examining whole-body protein turnover in humans, but has not been evaluated as an indicator to be used in the indicator amino acid oxidation (IAAO) method. The goal of this study was to determine whether the L-[1-(13C)]leucine isotope is an acceptable indicator by comparing it with an established tracer, L-[1-(13C)]lysine. Healthy men (n = 7; 29.9 +/- 4.8 y old) were fed in random order a diet with 7 graded intakes of phenylalanine without tyrosine. In the first study (n = 5), subjects were administered an excess leucine intake of 65 mg/(kg.d), and in the second study (n = 5), they were given the mean requirement of 45 mg/(kg.d) to determine whether leucine intake affected the pattern of response. Previous IAAO studies using lysine and phenylalanine demonstrated a clear pattern in 13CO2 production, i.e., increasing test amino acid intake resulted in a linear decrease to plateau, with a readily discernable breakpoint indicating the requirement. This pattern of production of 13CO2, indicates clear partitioning of the indicator amino acid between oxidation and protein synthesis. This was not observed with leucine at an intake of 65 mg/(kg.d). Conversely, at the lower leucine intake of 45 mg/(kg.d), a breakpoint was seen and a total aromatic amino acid requirement estimate that did not differ from that obtain using lysine as the indicator was obtained. In conclusion, leucine may be used as the indicator in the IAAO technique only when the daily intake leucine is given at its mean requirement level and the potential metabolic effects of other variables are taken into consideration.
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Affiliation(s)
- Jean W-C Hsu
- Department of Nutritional Sciences, University of Toronto, Toronto, ON, M5S 3E2, Canada
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Hsu JWC, Goonewardene LA, Rafii M, Ball RO, Pencharz PB. Aromatic amino acid requirements in healthy men measured by indicator amino acid oxidation. Am J Clin Nutr 2006; 83:82-8. [PMID: 16400054 DOI: 10.1093/ajcn/83.1.82] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND In the current literature, no agreement exists on estimates for aromatic amino acid (phenylalanine plus tyrosine) requirements as measured by stable-isotope techniques. OBJECTIVE The goal of the present study was to determine the phenylalanine requirement in healthy men who were fed a diet without tyrosine by using the indicator amino acid oxidation method. DESIGN Five healthy men were assigned to receive in random order diets devoid of tyrosine and with 8 graded intakes of phenylalanine (5, 10, 15, 25, 35, 45, 60, and 70 mg x kg(-1) x d(-1)). The phenylalanine requirement was measured by the rate of 13CO2 release (F13CO2) from L-[1-(13)C]lysine oxidation. RESULTS The graded intakes of phenylalanine had no effect on lysine flux, as required for this method. The phenylalanine (ie, total aromatic amino acid) requirement, in the absence of tyrosine, was estimated to be 48 mg x kg(-1) x d(-1) by applying a two-phase linear regression crossover model to the F13CO2 data. CONCLUSIONS In the absence of tyrosine, the mean phenylalanine requirement is higher than the current FAO/WHO/UNU (1985) and Dietary Reference Intake (2002) recommendations.
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Affiliation(s)
- Jean W-C Hsu
- Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
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Kurpad AV, Regan MM, Raj T, Gnanou JV. Branched-chain amino acid requirements in healthy adult human subjects. J Nutr 2006; 136:256S-63S. [PMID: 16365094 DOI: 10.1093/jn/136.1.256s] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
There is now an expanding body of evidence to recommend, in the case of adult humans, the use of revised indispensable amino acid requirement values; these are approximately 2 to 3 times higher than the current international recommendations. The earlier methodologies for determining amino acid requirements, based on nitrogen balance, were criticized because of their design and the associated high energy intakes. The 1985 World Health Organization/Food & Agriculture Organization/United Nations University requirement for leucine has been demonstrated to be too low by short- and long-term (24-h) tracer-derived estimates of leucine oxidation and balance. The best values for leucine requirements come from 24-h direct amino acid oxidation (DAAO) and direct amino acid balance (DAAB) studies. Finally, we also collated all available data from studies on fed-state leucine oxidation with an adequate dietary adaptation period to assess the inflection on the leucine oxidation-leucine intake curve. The mean requirements for leucine, valine, and isoleucine are likely to be 40, 17-25, and 19 mg . kg(-1) . d(-1), respectively. This adds up to a total of approximately 84 mg . kg(-1) . d(-1), which is much lower than the lowest estimate of the total BCAA requirement of approximately 110 mg . kg(-1) . d(-1) made by the short-term indicator amino acid oxidation (IAAO) method, which determined the BCAA requirement from the pattern of oxidation of an indicator amino acid (phenylyalanine) at different levels of BCAA intake. An additional estimate of the leucine requirement was also made by a meta-analysis of all available 24-h DAAO/DAAB data from different studies. This resulted in a higher value for the leucine requirement than that obtained by the specific studies that utilized the 24-h DAAO/DAAB approach; however, even adding this value to the total BCAA requirement does not account for the difference in the total BCAA requirement estimates and the summed individual BCAA estimates.
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Affiliation(s)
- Anura V Kurpad
- Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA.
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Kurpad AV, Regan MM, Raj TDS, Gnanou JV, Rao VN, Young VR. The daily valine requirement of healthy adult Indians determined by the 24-h indicator amino acid balance approach. Am J Clin Nutr 2005; 82:373-9. [PMID: 16087981 DOI: 10.1093/ajcn.82.2.373] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND The 1985 FAO/WHO/UNU requirement for valine was set at 10 mg x kg(-1) x d(-1) on the basis of nitrogen balance studies carried out in Western subjects. It is likely that the requirement is higher, however, because the requirement of another branched-chain amino acid, leucine, was found to be about 3 times as high (40 mg x kg(-1) x d(-1)) as the 1985 FAO/WHO/UNU value (14 mg x kg(-1) x d(-1)). OBJECTIVE We assessed the valine requirement in healthy, well-nourished Indians by using 7 test valine intakes (5, 10, 15, 20, 25, 30, and 35 mg x kg(-1) x d(-1)) and the 24-h indicator amino acid oxidation (24-h IAAO) and balance (24-h IAAB) method, with phenylalanine as the indicator amino acid, while maintaining leucine intake at 40 mg x kg(-1) x d(-1). DESIGN Eighteen healthy, well-nourished Indian men were studied during each of 3 randomly assigned 7-d diet periods supplying valine intakes that were equally placed on either side of a putative mean valine requirement of 20 mg x kg(-1) x d(-1). Twenty-four-hour IAAO and 24-h IAAB were measured on day 7 by use of a 24-h [13C]phenylalanine tracer infusion. The breakpoint in the relation between these values and the valine intake was determined. RESULTS Two-phase linear regression of daily phenylalanine oxidation or balance against valine intake estimated a breakpoint in the response curve at a valine intake of 17 mg x kg(-1) x d(-1) (95% Fieller's CI: 11, > 35 and 11, 28 mg x kg(-1) x d(-1), respectively). CONCLUSION From the 24-h IAAO/IAAB approach, a mean valine requirement of 17 mg x kg(-1) x d(-1) is proposed for healthy, well-nourished Indian adults.
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Affiliation(s)
- Anura V Kurpad
- Division of Nutrition, Institute of Population Health and Clinical Research, St John's National Academy of Health Sciences, Bangalore, India.
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Kurpad AV, Regan MM, Raj TDS, Gnanou JV, Rao VN, Young VR. The daily valine requirement of healthy adult Indians determined by the 24-h indicator amino acid balance approach. Am J Clin Nutr 2005. [DOI: 10.1093/ajcn/82.2.373] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Anura V Kurpad
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Meredith M Regan
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Tony DS Raj
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Justin V Gnanou
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Vidya N Rao
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
| | - Vernon R Young
- From the Division of Nutrition (AVK, TDSR, and VNR) and the Core Biochemistry Laboratory (JVG), Institute of Population Health and Clinical Research, St John’s National Academy of Health Sciences, Bangalore, India, and the Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA (MMR and VRY)
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Bertolo R, Pencharz P, Ball R. Chapter 6 Role of intestinal first-pass metabolism on whole-body amino acid requirements. BIOLOGY OF GROWING ANIMALS 2005. [DOI: 10.1016/s1877-1823(09)70013-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Kurpad AV, Regan MM, Varalakshmi S, Gnanou J, Lingappa A, Young VR. Effect of cystine on the methionine requirement of healthy Indian men determined by using the 24-h indicator amino acid balance approach. Am J Clin Nutr 2004; 80:1526-35. [PMID: 15585764 DOI: 10.1093/ajcn/80.6.1526] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The 1985 FAO/WHO/UNU requirement for methionine in healthy adults consuming a cystine-free diet is 13 mg.kg(-1).d(-1). It is unclear whether this daily requirement is influenced by dietary cystine. OBJECTIVE We assessed the effect of 2 intakes of cystine (5 and 12 mg.kg(-1).d(-1)) on methionine requirements in well-nourished Indian men by using 7 test methionine intakes (3, 6, 9, 13, 18, 21 and 24 mg.kg(-1).d(-1)) and the 24-h indicator amino acid oxidation (24-h IAAO) and balance (24-h IAAB) methods. We combined these data with those from an experiment with zero cystine intake and in which the exact same method was used. DESIGN Two studies were performed in which a diet containing either 5 or 12 mg cystine.kg(-1).d(-1) was fed to 21 well-nourished Indian men over three 7-d periods. The 24-h IAAO and 24-h IAAB values were measured on day 7 with the use of a 24-h intravenous [13C]leucine tracer infusion. The breakpoints in the relation between these values and methionine intake in each study were assessed by two-phase linear regression. RESULTS Breakpoints in the response curve were obtained at methionine intakes of 20 (95% Fiellers CI: 17, 26) and 10 (95% Fiellers CI: 8, 16) mg.kg(-1).d(-1) with cystine intakes of 5 and 12 mg.kg(-1).d(-1) intakes, respectively, which suggested a sparing effect of cystine. Although the 5- and 12-mg cystine breakpoints differed from one another, they did not differ significantly from that estimated previously with 0 mg cystine. CONCLUSION Cystine may spare the methionine requirement in healthy men, although the amount of sparing is difficult to quantify.
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Affiliation(s)
- Anura V Kurpad
- Division of Nutrition and the Biochemistry Laboratory, Institute of Population Health and Clinical Research, St John's National Academy of Health Sciences, Bangalore, India.
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Millward DJ. Vernon Young and the development of current knowledge in protein and amino acid nutrition. Vernon Young 1937–2004. Am J Clin Nutr 2004. [DOI: 10.1093/ajcn/80.5.1093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Sakai R, Miura M, Amao M, Kodama R, Toue S, Noguchi Y, Kimura T. Potential approaches to the assessment of amino acid adequacy in rats: a progress report. J Nutr 2004; 134:1651S-1655S; discussion 1664S-1666S, 1667S-1672S. [PMID: 15173446 DOI: 10.1093/jn/134.6.1651s] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We report on research progress on two approaches that may be useful in determining the upper adequacy range for macronutrients such as amino acids. One approach was to attempt to identify "toxic metabolites" that were responsible for toxicity or biomarkers for the toxicity of excessive intake of an amino acid in rats. We found that there was hepatic toxicity that was specifically associated with L-cystine excess, but not with L-cysteine excess. We analyzed urine samples from rats fed basal diets or L-cystine or L-cysteine excess diets and identified 25 peaks from gas chromatography mass spectrometry analysis that were specific for L-cystine excess and also correlated with toxicity markers. Another approach was to try to identify "metabolic limits" by measuring CO(2) arising from amino acid excess. Uniformly (13)C labeled L-leucine was used as tracer, in diets with added L-leucine fed to rats, and (13)CO(2) arising from its metabolism was collected over 24 h and the fraction of the ingested L-leucine that was exhaled as CO(2) was calculated. The fractional exhalation of (13)CO(2) increased with increasing L-leucine dose, but showed an inflexion point at approximately 8.9 g/kg body weight, after which it reached a plateau. This suggested that >8.9 g/kg BW, the catabolism of L-leucine changed and this approximately coincided with the dose above which a statistically significant decrease in body weight was seen.
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Affiliation(s)
- Ryosei Sakai
- Institute of Life Sciences and Research Institute for Health Fundamentals, Ajinomoto Co., Inc., Kawasaki, Japan
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Abstract
A full review of the strengths and limitations of the various methods used to define amino acid requirements is provided. The focus is on the recent development of carbon oxidation techniques such as indicator amino acid oxidation and 24-h amino acid balance to determine dietary indispensable (essential) amino acid needs in adults. All approaches depend on the change in a metabolic parameter in response to graded intake of the test amino acid. In humans, the within-subject variance is less than the between-subject variance, which has led to an appreciation of the need to study each subject across a range of intakes, above and below the mean requirement level. The data can then be analyzed using two-phase linear regression crossover and a precise population mean requirement can be determined. Several approaches have been used to define the variance of the mean requirement. Finally, a minimally invasive indicator amino acid oxidation model has been developed which allows the determination of dietary essential amino acid requirements in children and other vulnerable populations.
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Affiliation(s)
- Paul B Pencharz
- Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada.
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Kurpad AV, Regan MM, Varalakshmi S, Vasudevan J, Gnanou J, Raj T, Young VR. Daily methionine requirements of healthy Indian men, measured by a 24-h indicator amino acid oxidation and balance technique. Am J Clin Nutr 2003; 77:1198-205. [PMID: 12716672 DOI: 10.1093/ajcn/77.5.1198] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The 1985 FAO/WHO/UNU upper requirement for the sulfur-containing amino acids in healthy adults, which was set at 13 mg . kg(-)(1) . d(-)(1), is based on nitrogen balance studies in Western subjects. Short-term tracer-based studies also estimated a mean requirement of 13 mg . kg(-)(1) . d(-)(1), but whether this estimate is applicable to healthy populations worldwide is unknown. OBJECTIVE Using a 24-h indicator amino acid oxidation and balance method with 7 test methionine intakes (3, 6, 9, 13, 18, 21, and 24 mg . kg(-)(1) . d(-)(1)), we assessed methionine requirements in healthy, well-nourished Indians. DESIGN Twenty-one healthy, well-nourished Indian men were studied during each of 3 randomly assigned 7-d diet periods in which methionine intakes (diet devoid of cysteine) were equally placed on either side of the putative mean methionine requirement of 13 mg . kg(-)(1) . d(-)(1). Twenty-four-hour indicator amino acid oxidation and balance were measured on day 7 by using a 24-h [(13)C]leucine tracer infusion. The breakpoint in the relation between these values and the methionine intake was determined. RESULTS Two-phase linear regression of daily leucine oxidation against methionine intake estimated a breakpoint in the response curve at a methionine intake of 14 mg . kg(-)(1) . d(-)(1) (95% CI: 11, 23 mg . kg(-)(1) . d(-)(1)). The breakpoint estimated from the leucine balance-methionine intake relation was 15 mg . kg(-)(1) . d(-)(1) (95% CI: 11, 27 mg . kg(-1) . d(-1)). CONCLUSIONS From the 24-h indicator amino acid oxidation and balance approach, a mean methionine requirement, in the absence of cysteine intake, of 15 mg . kg(-1) . d(-1) is proposed for healthy, well-nourished Indian adults. This requirement is similar to that established in Western adults.
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Affiliation(s)
- Anura V Kurpad
- Department of Physiology and Division of Nutrition, St John's Medical College, Bangalore, India
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Kurpad AV, Regan MM, Raj T, Varalakshmi S, Gnanou J, Thankachan P, Young VR. Leucine requirement and splanchnic uptake of leucine in chronically undernourished adult Indian subjects. Am J Clin Nutr 2003; 77:861-7. [PMID: 12663284 DOI: 10.1093/ajcn/77.4.861] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND We showed previously by the 24-h direct amino acid balance (DAAB) method that the leucine requirement of well-nourished Western and South Asian subjects is approximately 40 mg x kg(-1) x d(-1). OBJECTIVE It is not known whether this estimated leucine requirement is applicable in chronic undernutrition; therefore, we assessed the leucine requirement in Indian men with chronic, but stable, undernutrition. DESIGN We studied 26 chronically undernourished men during 2 randomly assigned 7-d diet periods consisting of an L-amino acid diet (n = 20) and supplying either 14 and 30 (n = 10) or 22 and 40 (n = 10) mg leucine x kg(-1)x d(-1) or consisting of the subjects' habitual cereal-and-lentil-based diets (n = 6). The 24-h DAAB was estimated on day 6 by using a [13C]leucine tracer infusion. The splanchnic uptake of leucine was determined at an intake of 40 mg x kg(-1) x d(-1) by administering [2H3]leucine orally. RESULTS By using mixed-models linear regression of leucine balance against leucine intake, we estimated a zero leucine balance at a leucine intake of 39.6 mg x kg(-1) x d(-1). The splanchnic first-pass uptake of [2H3]leucine was 22.7% and 11.5% of the intake in the fasted and fed phases, respectively. The subjects were in neutral leucine balance with their habitual cereal-and-lentil-based diets. CONCLUSION On the basis of the 24-h DAAB approach, a mean leucine requirement of 40 mg x kg(-1) x d(-1) is proposed for healthy and for chronically undernourished Indian adults.
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Affiliation(s)
- Anura V Kurpad
- Department of Physiology and Division of Nutrition, St John's Medical College, Bangalore, India
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Kurpad AV, Young VR. What is apparent is not always real: lessons from lysine requirement studies in adult humans. J Nutr 2003; 133:1227-30. [PMID: 12672948 DOI: 10.1093/jn/133.4.1227] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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