Safety of Amino Acids

Safety Studies of Amino Acids in Animals

Amino Acid Animal Method of administration Duration
(recovery period)
Dose Reference
Indispensable Amino Acids
L-histidine Fischer rat Mixed food 13W 0.31, 0.62, 1.25, 2.5, 5% (w/w) [Japanese]
Ikezaki S, Nishikawa A, et al.
"13-week subchronic toxicity study of L-histidine monohydrochloride in F344 rats"
Bull Natl Ins Health Sci (1994), 112:57-63
L-isoleucine SD rat Mixed food 13W (5W) 1.25, 2.5, 5% (w/w) Tsubuku S, Hatayama K, et al.
Thirteen-week oral toxicity study of branched-chain amino acids in rats
Int J Toxicol (2004), 23(2):119-126
L-leucine SD rat Mixed food 13W (5W) 1.25, 2.5, 5% (w/w) Tsubuku S, Hatayama K, et al.
Thirteen-week oral toxicity study of branched-chain amino acids in rats
Int J Toxicol (2004), 23(2):119-126
L-lysine/HCl SD rat Mixed food 13W (5W) 1.25, 2.5, 5% (w/w) Tsubuku S, Mochizuki M, et al.
Thirteen-week oral toxicity study of L-lysine hydrochloride in rats
Int J Toxicol (2004), 23(2):113-118
L-methionine Fischer rat ♂ Mixed food 4W 0.1, 0.3, 0.9, 2.7% (w/w) Chin K, Toue S, et al.
"A 4-week toxicity study of methionine in male rats"
Int J Toxicol (2015), 34(3):233-241
L-phenylalanine SD rat Mixed food 28 days 0.5, 1.5, 5.0% Shibui Y, Miwa T, et al.
"28-Day dietary toxicity study of L-phenylalanine in rats"
Fund Toxicol Sci (2014), 1(2):29-38
L-threonine SD rat Mixed food 13W (5W) 1.25, 2.5, 5.0% Aoki M, Ishida S, et al.
"A 13-week feeding toxicity study of L-threonine in rats with a recovery period of 5 weeks"
Fund Toxicol Sci (2014), 1(2):49-62
L-tryptophan SD rat Mixed food 13W (5W) 1.25, 2.5, 5.0% Shibui Y, Matsumoto H, et al.
+LOAEL(mg/kg/day) was calicurated using original research data (BW for LOAEL).
"Thirteen week toxicity study of dietary L‐tryptophan in rats with a recovery period of 5 weeks"
J Appl Toxicol (2018), 38(4): 552-563
L-valine SD rat Mixed food 13W (5W) 1.25, 2.5, 5% (w/w) Tsubuku S, Hatayama K, et al.
Thirteen-week oral toxicity study of branched-chain amino acids in rats
Int J Toxicol (2004), 23(2):119-126
Dispensable Amino Acids
L-alanine SD rat Gavage 4W (2W) 2,000mg/kg/day Aoki M, Mochizuki M, et al.
A 4-week oral toxicity study of L-alanine in rats with a recovery period of 2 weeks
Fund Toxicol Sci (2014), 1(2):63-72
L-arginine SD rat Mixed food 13W (5W) 1.25, 2.5, 5% (w/w) Tsubuku S, Hatayama K, et al.
Thirteen-week oral toxicity study of L-arginine in rats
Int J Toxicol (2004), 23(2):101-105
Pig Mixed food twice a day 13W 1.21, 1.81, 2.42% (w/w)
Hu S, Li X, et al.
Safety of long-term dietary supplementation with L-arginine in pigs
Amino Acids (2015), 47(5):925-936
Mixed food twice a day 13W 1.0, 1.5, 2.0% (w/w)
SD rat Drinking water
13W 2.18, 4.35 g/kg/day
Yang Y, Wu Z, et al.
Safety of long‑term dietary supplementation with L‑arginine in rats
Amino Acids (2015), 47(9):1909-1920
L-asparagine Fischer rat Mixed food 90 days 1.25, 2.5, 5% (w/w) Yokohira M, Hosokawa K, et al.
"A 90-day toxicity study of L-asparagine, a food additive, in F344 rats"
Food Chem Toxicol (2008), 46(7):2568-2572
L-aspartic acid Fischer rat Mixed food 90 days 0.05, 1.25, 2.5, 5.0% (w/w) Tada Y, Yano N, et al.
"Toxic effects of L-aspartic acid at high dose levels on kidneys and salivary glands in Fischer 344 rats detected in a 90-day feeding study"
Food Chem Toxicol (2008), 46(8):2789-2795
L-cysteine SD rat Gavage 4W 500, 1000, 2000 mg/kg/day Shibui Y, Sakai R, et al.
"Comparisons of L-cysteine and D-cysteine toxicity in 4-week repeated-dose toxicity studies of rats receiving daily oral administration"
J Toxicol Pathol (2017), 30(3):217-229
L-glutamate - - - - Acceptable daily intake (ADI) is not specified in JECFA report. ADI can be driven from NOAEL, so that NOAEL of L-Glu/Na is not also specified.: Principles for the safety assessment of food additives and contaminants in food. World Health Organization
International Program on Chemical Safety in Cooperation with the Joint FAO/WHO Expert Committee on Food Additives, Geneva, Environmental Health Criteria 70 (1987).
CD-1 mouse Mixed food 3-genaration reproductive toxicity:
F0:Gestation & lactation
F1: Postweaning – Lactation
F2: Postweaning – Lactation
F3: Birth - Weaning
1.0, 4.0% (w/w) Anantharaman K
In utero and dietary administration of monosodium L-glutamate to mice: Reproductive performance and development in a multigeneration study
Glutamic Acid: Advances in Biochemistry and Physiology, ed. by Filer LJ, et al., Raven Press, NY (1979):231-253
L-glutamine SD rat Mixed food 13W (5W) 1.25, 2.5, 5% (w/w) Tsubuku S, Hatayama K, et al.
Thirteen-week oral toxicity study of L-glutamine in rats.
Int J Toxicol (2004), 23(2):107-112
L-glycine SD rat Gavage 28 days 500, 1000, 2000 mg/kg/day Shibui Y, Miwa T, et al.
"A 4-week repeated dose toxicity study of glycine in rats by gavage administration"
J Toxicol Pathol (2013), 26(4) 405–412, 2013
L-proline Fischer rat Mixed food 90 days 0.625, 1.25, 2.5, 5.0% Tada Y, Yano N, et al.
"Toxicological evaluation of L-proline in a 90-day feeding study with Fischer 344 rats"
Regul Toxicol Pharmacol (2010), 58(1):114-120
L-serine SD rat Gavage 13W 500, 1500, 3000 mg/kg/day Kaneko I, Han L, et al.
"A 13-week subchronic oral toxicity study of L-serine in rats"
Food Chem Toxicol (2009), 47(9):2356-2360
Fischer rat Mixed food 90 days 0.06, 0.5, 1.5, 5.0% Tada Y, Yano N, et al.
"A 90-day feeding toxicity study of L-serine in male and female Fischer 344 rats"
J Toxicol Pathol (2010), 23(1):39-47
L-tyrosine SD rat Gavage 13W 200, 600, 2000 mg/kg/day Shibui Y, Manabe Y, et al.
"13-week repeated dose toxicity study of l-tyrosine in rats by daily oral administration"
Food Chem Toxicol (2016), 87:55-64
Non-code protein Amino Acids
L-ornithine SD rat Mixed food 13W (5W) 1.25, 2.5, 5.0% Ishida S, Sarada M, et al.
"Genotoxicity and subchronic oral toxicity of L-ornithine monohydrochloride"
Regul Toxicol Pharmacol (2013), 67(3):360-71
L-citrulline SD rat Gavage 4W 2000 mg/kg/day Morita M, Yamaguchi T, et al.
"A 4-week oral gavage toxicity study of L-citrulline in rats"
Fund Toxicol Sci (2017), 4(5):219-227
L-hydroxyproline SD rat Gavage 28 days (14 days) 40, 200, 1000, 4000 mg/kg/day
Akiduki S, Kawada Y, et al.
Twenty-eight-day oral toxicity study of L-hydroxyproline in rats with 14-day post-treatment observation period
Fund Toxicol Sci (2019), 6(3):65-74

Safety Studies of Amino Acids in Human

Amino Acid Category Subject Method of administration Duration Dose Reference
Review
Amino acids Safety Review - - - - Elango R.
Tolerable Upper Intake Level for Individual Amino Acids in Humans: A Narrative Review of Recent Clinical Studies
Advances in Nutrition (2023), 14(4): 885-894.
Safety Review - - - - Blachier F, et al.
Tolerable amounts of amino acids for human supplementation: summary and lessons from published peer-reviewed studies
Amino Acids (2021) 53(9):1313-1328
Indispensable Amino Acids
L-histidine Safety Assessment Study Healthy adults (male and female) Oral 4W 4, 8, 12, 16 g/day Gheller ME, et al.
Tolerance to graded dosages of histidine supplementation in healthy human adults
American Journal of Clinical Nutrition (2020), 112(5): 1358-1367.
Safety Review - - - - Thalacker-Mercer AE, et al.
Benefits and Adverse Effects of Histidine Supplementation
The Journal of Nutrition (2020), 150(Suppl1), 2588S-2592S.
Safety Review - - - - Cynober L, et al.
Proposals for Upper Limits of Safe Intake for Methionine, Histidine, and Lysine in Healthy Humans
The Journal of Nutrition (2020)150(Suppl1):2606S-2608S,
L-isoleucine
L-leucine Safety Assessment Study Healthy adults (male) Oral Once 50, 150, 250, 500, 750, 1000, 1250 mg/kg/day Elango R, et al.
Determination of the tolerable upper intake level of leucine in acute dietary studies in young men
American Journal of Clinical Nutrition (2012), 96(4):759-767.
Safety Review - - - - Cynober L, et al.
Proposals for Upper Limits of Safe Intake for Arginine and Tryptophan in Young Adults and an Upper Limit of Safe Intake for Leucine in the Elderly
The Journal of Nutrition (2016), 146(12):2652S-2654S.
Safety Review - - - - Pencharz PB, et al.
Determination of the tolerable upper intake level of leucine in adult men
The Journal of Nutrition (2012), 142(12):2220S-2224S.
L-lysine/HCl Safety Review - - - - Hayamizu K, et al.
Safety assessment of L-lysine oral intake: a systematic review
Amino Acids (2019), 51(4):647-659.
Safety Review - - - - Cynober L, et al.
Proposals for Upper Limits of Safe Intake for Methionine, Histidine, and Lysine in Healthy Humans
The Journal of Nutrition (2020)150(Suppl1):2606S-2608S,
L-methionine Safety Assessment Study Healthy older adults Oral 4W 9.2, 22.5, 46.3, 91 mg/kg/day Deutz NE, et al.
Tolerance to increased supplemented dietary intakes of methionine in healthy older adults
American Journal of Clinical Nutrition (2017) 106(2):675-683.
Safety Review - - - - Ligthart-Melis GC. et al.
Metabolic Consequences of Supplemented Methionine in a Clinical Context
The Journal of Nutrition (2020)150(Suppl1):2538S-2547S,
Safety Review - - - - Cynober L, et al.
Proposals for Upper Limits of Safe Intake for Methionine, Histidine, and Lysine in Healthy Humans
The Journal of Nutrition (2020)150(Suppl1):2606S-2608S,
Case Study Patients with coronary artery or peripheral arterial disease Oral Once 100 mg/kg Krupkova-Meixnerova L, et al.
Methionine-loading test: evaluation of adverse effects and safety in an epidemiological study
Nutrition(2002), 21(2):151-156.
Case Study Healthy nonsmoking adults and patients with several thrombotic conditions. Oral Once 100 mg/kg Majluf-Cruz A, et al.
Safety of the oral methionine load test: effects on the clinical performance and laboratory tests
Revista de Investigacion Clinica (2013), 65(4):323-330.
L-phenylalanine Safety Assessment Study Healthy adults (male) Oral 4W 3, 6, 9, 12 g/day Miura N. et al.
Subchronic Tolerance Trials of Graded Oral Supplementation with Phenylalanine or Serine in Healthy Adults
Nutrients (2021) 13(6): 1976
Safety Review - - - - Blachier F, et al.
Tolerable amounts of amino acids for human supplementation: summary and lessons from published peer-reviewed studies
Amino Acids (2021) 53(9):1313-1328
Case Study Healthy, active male Oral Once 3g Ueda K. et al.
The effects of phenylalanine on exercise-induced fat oxidation: a preliminary, double-blind, placebo-controlled, crossover trial
Journal of the International Society of Sports Nutrition (2017), 14:34.
L-threonine Case Study Patients with familial spastic paraparesis (FSP) Oral 2W 4.5, 6 g/day Growdon J.H. et al.
L-Threonine in the Treatment of Spasticity
Clinical neuropharmacology (1991), 14(5):403-412.
Case Study Patients with spinal spasticity Oral - 6 g/day Lee A. and Patterson V.
A double-blind study of L-threonine in patients with spinal spasticity
Acta Neurologica Scandinavica (1993), 88(5):334-338.
Case Study Patients with amyotrophic lateral sclerosis (ALS) Oral 6M 4 g/day Tandan R. et al.
A controlled trial of amino acid therapy in amyotrophic lateral sclerosis
Neurology (1996), 47(5):1220-1226.
L-tryptophan Safety Assessment Study Healthy Japanese women Oral 21D 1, 2, 3, 4, 5 g/day Hiratsuka C, et al.
Supplementing healthy women with up to 5.0 g/d of L-tryptophan has no adverse effects
The Journal of Nutrition (2013), 143(6):859-866
Safety Review - - - - Cynober L, et al.
Proposals for Upper Limits of Safe Intake for Arginine and Tryptophan in Young Adults and an Upper Limit of Safe Intake for Leucine in the Elderly
The Journal of Nutrition (2016), 146(12): 2652S-2654S.
L-valine
Dispensable Amino Acids
L-alanine Case Study Therapeutically starved obese subjects Oral 1D 50 g Genuth SM.
Effects of oral alanine administration in fasting obese subjects
Metabolism. 22(7), 1973, 927-937.
L-arginine Safety Review - - - - Cynober L, et al.
Proposals for Upper Limits of Safe Intake for Arginine and Tryptophan in Young Adults and an Upper Limit of Safe Intake for Leucine in the Elderly
The Journal of Nutrition (2016), 146(12): 2652S-2654S.
Safety Review - - - - Shao A, et al.
Risk assessment for the amino acids taurine, L-glutamine and L-arginine
Regulatory Toxicology and Pharmacology (2008), 50(3):376-399,
Safety Assessment Study Adults (male and female) Oral 90D 0, 15, 30 g/day McNeal CJ, et al.
Safety of dietary supplementation with arginine in adult humans.
Amino Acids (2018), 50(9):1215-1229.
L-asparagine
L-aspartic acid Case Study - Oral - 5, 10 g Harold EC. et al.
Stimulation of pituitary hormone secretion by neurotransmitter amino acids in humans.
Metabolism. 38(12), 1989, 1179-1182.
L-cysteine Case Study - Oral - 5, 10 g Harold EC. et al.
Stimulation of pituitary hormone secretion by neurotransmitter amino acids in humans.
Metabolism. 38(12), 1989, 1179-1182.
L-glutamate Safety Review - - - - Acceptable daily intake (ADI) is not specified in JECFA report. ADI can be driven from NOAEL, so that NOAEL of L-Glu/Na is not also specified.: Principles for the safety assessment of food additives and contaminants in food. World Health Organization
Safety Review - - - - International Program on Chemical Safety in Cooperation with the Joint FAO/WHO Expert Committee on Food Additives, Geneva, Environmental Health Criteria 70 (1987).
L-glutamine Safety Assessment Study Healthy adults (male), HIV patients with AIDS-associated weight loss and cancer patients with wasting Oral - 14 g Rathmacher JA. et al.
Supplementation with a combination of beta-hydroxy-beta-methylbutyrate (HMB), arginine, and glutamine is safe and could improve hematological parameters
Journal of Parenteral and enteral nutrition (2004) 28(2):65-75.
Safety Review - - - - Shao A, et al.
Risk assessment for the amino acids taurine, L-glutamine and L-arginine
Regulatory Toxicology and Pharmacology (2008), 50(3):376-399,
Case Study Healthy adults (male) Oral 1D 0.3, 0.6, 0.9 g/kg·FFM Ogden HB, et al.
Gastrointestinal Tolerance of Low, Medium and High Dose Acute Oral l-Glutamine Supplementation in Healthy Adults: A Pilot Study
Nutrients (2020) 12(10):2953.
Glycine Safety Assessment Study Healthy adults (male and female) Oral 7D 9 g/day Inagawa K, et al.
Assessment of Acute Adverse Events of Glycine Ingestion at a High Dose in Human Volunteers
Journal of Urban Living and Health Association (2006), 50(1):27-32.
L-proline
L-serine Safety Assessment Study Healthy adults (male) Oral 4W 3, 6, 9, 12 g/day Miura N. et al.
Subchronic Tolerance Trials of Graded Oral Supplementation with Phenylalanine or Serine in Healthy Adults
Nutrients (2021) 13(6): 1976
Safety Review - - - - Blachier F, et al.
Tolerable amounts of amino acids for human supplementation: summary and lessons from published peer-reviewed studies
Amino Acids (2021) 53(9):1313-1328
L-tyrosine Case Study Patients with essential hypertension Oral 2W 7.5 g/day Sole MJ. Et al.
Chronic dietary tyrosine supplements do not affect mild essential hypertension
Hypertension (1985), 7(4):593-596.
Case Study Subjects with narcolepsy and cataplexy Oral 4W 9 g/day Elwes RDC. et al.
Treatment of narcolepsy with L-tyrosine: double-blind placebo-controlled trial
The Lancet (1989), 334(8671):1067-1069.
Case Study - Oral 1D 150 mg/day Neri DF. et al.
The effects of tyrosine on cognitive performance during extended wakefulness
Aviation, Space and Environmental Medicine (1995), 66(4):313-319.
Case Study Patients with nemaline myopathy Oral - 250 to 3000 mg/day Monique MR. et al.
Dietary L-tyrosine supplementation in nemaline myopathy
Journal of Child Neurology (2008),23(6):609-13.
Non-code protein Amino Acids
L-ornithine/HCl Safety Assessment Study Healthy adults (male) Oral 4W 3.2, 6, 9.2, 12 g/day Miura N. et al.
Subchronic tolerance trials of graded oral supplementation with ornithine hydrochloride or citrulline in healthy adults
Amino Acid (2022); 1-13.
Case Study Healthy adults (male and female) Oral - 2000 mg/day for 7D and 6000 mg/day for 1D Sugino T. et al.
L-ornithine supplementation attenuates physical fatigue in healthy volunteers by modulating lipid and amino acid metabolism
Nutrition Research (2008), 28(11):738-743.
L-citruline Safety Assessment Study Healthy adults (male) Oral 4W 6, 12, 18, 24 g/day Miura N. et al.
Subchronic tolerance trials of graded oral supplementation with ornithine hydrochloride or citrulline in healthy adults
Amino Acid (2022); 1-13.
Case Study Healthy adults (male) Oral 1D 2, 5, 10, 15 g Moinard C. et al.
Dose-ranging effects of citrulline administration on plasma amino acids and hormonal patterns in healthy subjects: the Citrudose pharmacokinetic study
British Journal of Nutrition (2008), 99(4):855-862.
L-hydroxyproline