L-Cysteine and Cysteine Information

L-cysteine is a protein amino acid that exists naturally as a protein in most living organisms. Although most cysteine is found in proteins, small amounts of cysteine are also located in body fluids and in plants in non-protein form. The average diet of most individuals contributes approximately 1 gram of L-cysteine daily.

L-cysteine is considered a nonessential amino acid, meaning that sufficient amounts are produced by the body itself. Cysteine is one of the few amino acids containing sulfur. This allows cysteine to bond in a special way and to maintain the structure of proteins in the body.

L-cysteine aids in the synthesis of proteins, glutathione, taurine, coenzyme A, and inorganic sulfate in the body. Glutathionine itself has a number of biochemical functions, including maintenance of normal cellular redox state. Certain conditions, e.g. an acetaminophen overdose, can deplete hepatic glutathione, and this can be life-threatening. The antidote to an acetaminophen overdose is L-cysteine in the delivery form of N-acetylcysteine. The L-cysteine derived from N-acetylcysteine helps to restore hepatic glutathione.

Medical Indications

Cysteine can also be transformed into glucose and used by the body as a source of energy. Cysteine strengthens the protective lining of the stomach and intestines, which may help prevent damage caused by aspirin and similar drugs. Additionally, cysteine may play an important role in the communication between immune system cells. Cysteine is rarely used as a dietary supplement. N-acetyl cysteine (NAC), which contains cysteine, is more commonly used as a supplement.

Dosage and Administration

The usual supplemental dosage of L-cysteine is 500 milligrams to 1.5 grams daily. Those who supplement with L-cysteine should drink at least six to eight glasses of water daily in order to prevent cystine renal stones.