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

Authors

Naoki Miura
Hideki Matsumoto
Luc Cynober
Patrick J Stover
Rajavel Elango
Motoni Kadowaki
Dennis M Bier
Miro Smriga

Language

English

Publication Date

6-8-2021

Journal

Nutrients

DOI

10.3390/nu13061976

PMID

34201370

PMCID

PMC8227932

PubMedCentral® Posted Date

6-8-2021

PubMedCentral® Full Text Version

Post-print

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.

Keywords

Administration, Oral, Adult, Body Weight, Dietary Supplements, Energy Intake, Female, Health, Humans, Male, Mental Fatigue, Nutrients, Phenylalanine, Serine, Sleep

Published Open-Access

yes

Recommended Citation

Miura, Naoki; Matsumoto, Hideki; Cynober, Luc; et al., "Subchronic Tolerance Trials of Graded Oral Supplementation with Phenylalanine or Serine in Healthy Adults" (2021). Children’s Nutrition Research Center Staff Publications. 4.
https://digitalcommons.library.tmc.edu/staff_pub/4