What is Citrulline

Chemical Name: (S)-2-amino-3-phenylpropanoic acid

Molecular Weight: 175.19

Structrual Formula: H2N-CONH-CH2-CH2-CH2-CHNH2-COOH

Nitrogen Content: 23.97%

Citrulline (13, 117)

  • Citrulline is a nonessential amino acid, which means that it is manufactured from other amino acids in the liver; it does not have to be obtained directly through the diet
  • Citrulline is found in high concentration in the liver
  • It influences the production of growth hormone, and is used for the detoxification of ammonia and in the treatment of fatigue
  • L-Citrulline is a precursor to the formation of L-Arginine and thus plays a vital role in Arginine recycling, which is an important factor in nitric oxide release
  • supports the body in optimizing blood flow through its conversion to L-arginine and then nitric oxide
  • Nitric oxide is involved in vasodilatation and low levels are associated with mental and physical fatigue and sexual dysfunction

Citrulline and urea cycle (118,119)

  • The amino acid citrulline is required to detoxify the liver from ammonia, which is a waste product of the body from oxidation
  • Citrulline promotes energy and assists with the immune system. This unusual amino acid is formed in the urea cycle by the addition of carbon dioxide and ammonia to ornithine
  • It is then combined with aspartic acid to form arginosuccinic acid, which later is metabolized into the amino acid arginine
  • Citrulline is a precursor to arginine and is involved in the formation of urea in the liver
  • The synthesis and elimination of urea is essential for removing toxic nitrogen metabolites from the body
  • These metabolites build up from the digestion, absorption, and metabolism of protein
  • Citrulline works along with aspartic acid, citric acid, and magnesium in helping to improve nitrogen metabolite excretion

Citrulline and Food

  • Citrulline can be found in abundance in plant foods such as onion and garlic

Best used with Citrulline

  • Zinc and vitamin B6 are useful for promoting the conversion of citrulline to arginine

Characteristic symptoms of elevated levels of citrulline (61)

  • Hyperammonemia
  • persistent vomiting
  • ataxia (loss of muscle coordination)
  • Seizures
  • progressive mental retardation


  • 13) Balch, James, MD, and Phyllis Balch, CNC, Prescription for Nutritional Healing, Avery Pub., 1997.
  • 117) Cynober, L, editor, Amino Acid Metabolism & Therapy in Health & Nutritional Diseases, 1995.
  • 118) Husson A, Brasse-Lagnel C, Fairand A, Renouf S, Lavoinne A. Argininosuccinate synthetase from the urea cycle to the citrulline-NO cycle. Eur J Biochem. 2003 May;270(9):1887-99.
  • 61) Peter J. Garlick. The Nature of Human Hazards Associated with Excessive Intake of Amino Acids. J. Nutr. 2004 134: 1633-1639.
  • 119) Moinard Chirtophe et al. Citrulline: A new Player in the Control of Nitrogen Homeostais. American Society for Nutrition J., Nutr. 137:1621S-1625S