Nutritionally non-essential amino acids are dispensable for whole-body protein synthesis after exercise in endurance athletes with an adequate essential amino acid intake
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The increased protein requirement of endurance athletes may be related to the need to replace exercise-induced oxidative losses, especially of the branched-chain amino acids (BCAA). However, it is unknown if non-essential amino acids (NEAA) influence the requirement for essential amino acids (EAA) during post-exercise recovery. Seven endurance-trained males ran 20 km prior to consuming [13C]phenylalanine, sufficient energy, and: (1) deficient protein (BASE); (2) BASE supplemented with sufficient BCAA (BCAAsup); (3) an equivalent EAA intake as BCAA (LowEAA), and; (4) sufficient EAA intake (HighEAA). [13C]Phenylalanine oxidation (the reciprocal of protein synthesis) for BCAAsup and HighEAA (0.54 ± 0.15, 0.49 ± 0.11 µmol kg−1 h−1; Mean ± SD) were significantly lower than BASE (0.74 ± 0.14 µmol kg−1 h−1; P < 0.01 for both) and LowEAA (0.70 ± 0.11 µmol kg−1 h−1; P < 0.05 and 0.01, respectively). Our results suggest that exogenous NEAA are dispensable for whole-body protein synthesis during recovery from endurance exercise provided sufficient EAA are consumed. Endurance athletes who may be at risk of not meeting their elevated protein requirements should prioritize the intake of EAA-enriched foods and/or supplements.
KeywordsEndurance training Amino acid requirement Post-exercise recovery Protein synthesis Non-essential amino acids
Low protein diet
Branched-chain amino acids
BASE supplemented branched-chain amino acids
Essential amino acid
Exercise-induced energy expenditure
High dose of essential amino acids
Indicator amino acid oxidation
Low dose of essential amino acids
Non-essential amino acid
Whole-body phenylalanine flux
Recommended daily allowance
Resting energy expenditure
The authors’ responsibilities were as follows: HK and DRM designed the research; HK, KAV and DW conducted research and analyzed the data; HK performed the statistical analysis; HK and DRM wrote the manuscript with assistance from KAV and DW; KS consulted the study design and manuscript writing. HK and DRM had primary responsibility for final content. All authors read and approved the final manuscript.
This study was funded by Ajinomoto Co., Inc.
Compliance with ethical standards
Conflict of interest
Some of the authors (HK and KS) are employees of Ajinomoto. DRM has received research grant from Ajinomoto Co., Inc.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This study was approved by the research ethics board of the University of Toronto (No. 33245) and the institutional review board of Ajinomoto Co., Inc (No. 2016-017). This trial was registered at clinicaltrial.gov as NCT02874638.
Informed consent was obtained from all individual participants included in the study, after informing the purpose of the study, the experimental procedures involved and all the potential risks involved.
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