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Nutrients
Volume 13
Issue 6
10.3390/nu13061976
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Article

Subchronic Tolerance Trials of Graded Oral Supplementation with Phenylalanine or Serine in Healthy Adults

by
Naoki Miura
1,
Hideki Matsumoto
2,
Luc Cynober
3,4,
Patrick J. Stover
4,5,
Rajavel Elango
4,6,
Motoni Kadowaki
4,7,
Dennis M. Bier
4,8 and
Miro Smriga
9,*
1
Miura Medical Clinic, Higashitenma, Osaka 530-0044, Japan
2
Japan Branch of International Council for Amino Acid Science (ICAAS), Hatchobori, Tokyo 104-032, Japan
3
Clinical Chemistry Lab., Cochin Hospital, Paris and Biological Nutrition Lab. and EA 4466, Faculty of Pharmacy, Université de Paris, 75014 Paris, France
4
Scientific Advisory Committee of the International Council for Amino Acid Science (ICAAS), Avenue de Tervueren, 1150 Brussels, Belgium
5
Texas A & M AgriLife, College Station, TX 77843, USA
6
School of Population and Public Health, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
7
Department of Engineering, Niigata Institute of Technology, Niigata 950-0932, Japan
8
USDA/ARS Children’s Nutrition Research Center, Baylor College of Medicine, Houston, TX 77030, USA
9
International Council for Amino Acid Science (ICAAS), Avenue de Tervueren, 1150 Brussels, Belgium
*
Author to whom correspondence should be addressed.
Academic Editor: Gary David Lopaschuk
Nutrients 2021, 13(6), 1976; https://doi.org/10.3390/nu13061976
Received: 28 April 2021 / Revised: 4 June 2021 / Accepted: 5 June 2021 / Published: 8 June 2021
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Abstract

Phenylalanine and serine are amino acids used in dietary supplements and nutritional products consumed by healthy consumers; however, the safe level of phenylalanine or serine supplementation is unknown. The objective of this study was to conduct two 4-week clinical trials to evaluate the safety and tolerability of graded dosages of oral phenylalanine and oral serine. Healthy male adults (n = 60, 38.2 ± 1.8y) completed graded dosages of either phenylalanine or serine supplement (3, 6, 9 and 12 g/d) for 4 weeks with 2-week wash-out periods in between. Primary outcomes included vitals, a broad spectrum of circulating biochemical analytes, body weight, sleep quality and mental self-assessment. At low dosages, minor changes in serum electrolytes and plasma non-essential amino acids glutamine and aspartic acid concentrations were observed. Serine increased its plasma concentrations at high supplemental dosages (9 and 12 g/day), and phenylalanine increased plasma tyrosine concentrations at 12 g/day, but those changes were not considered toxicologically relevant. No other changes in measured parameters were observed, and study subjects tolerated 4-week-long oral supplementation of phenylalanine or serine without treatment-related adverse events. A clinical, no-observed-adverse-effect-level (NOAEL) of phenylalanine and serine supplementation in healthy adult males was determined to be 12 g/day. View Full-Text
Keywords: phenylalanine; serine; NOAEL; human; safety; dietary supplements phenylalanine; serine; NOAEL; human; safety; dietary supplements
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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MDPI and ACS Style

Miura, N.; Matsumoto, H.; Cynober, L.; Stover, P.J.; Elango, R.; Kadowaki, M.; Bier, D.M.; Smriga, M. Subchronic Tolerance Trials of Graded Oral Supplementation with Phenylalanine or Serine in Healthy Adults. Nutrients 2021, 13, 1976. https://doi.org/10.3390/nu13061976

AMA Style

Miura N, Matsumoto H, Cynober L, Stover PJ, Elango R, Kadowaki M, Bier DM, Smriga M. Subchronic Tolerance Trials of Graded Oral Supplementation with Phenylalanine or Serine in Healthy Adults. Nutrients. 2021; 13(6):1976. https://doi.org/10.3390/nu13061976

Chicago/Turabian Style

Miura, Naoki, Hideki Matsumoto, Luc Cynober, Patrick J. Stover, Rajavel Elango, Motoni Kadowaki, Dennis M. Bier, and Miro Smriga. 2021. "Subchronic Tolerance Trials of Graded Oral Supplementation with Phenylalanine or Serine in Healthy Adults" Nutrients 13, no. 6: 1976. https://doi.org/10.3390/nu13061976

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