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Vitamins, Minerals and Dietary Supplements

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Cysteine

What is cysteine? What do we need it?

Cysteine is a non-essential amino acid, a building block of proteins that occurs naturally in the human body. It can be synthesized from methionine and other amino acids, and acts as a component of other amino acids. Cysteine is one of the few amino acids that contains sulfur, which allows it to bond to other proteins and maintain the structure of those proteins.

Cysteine helps to strengthen the protective lining of the stomach and intestines, which can reduce the risk of ulcers and lessen the damage caused to the stomach and intestines by aspirin and similar drugs. Cysteine also plays an important role in the immune system by improving communication between different types of immune cells. In addition, it can be converted into glucose to provide the body with extra energy. Some studies suggest that patients with HIV have low cysteine levels in the blood; as a result, low levels may contribute to a suppressed immune system.

How much cysteine should I take?

Because it is produced naturally in the body, cysteine is usually not consumed as a supplement. However, a variation of the amino acid, n-acetyl cysteine (which contains cysteine), is often sold as a dietary supplement. Most clinical research has been conducted on n-acetyl cysteine; as a result, little is known about the appropriate levels or consumption of cysteine.

What forms of cysteine are available?

Cysteine occurs naturally in the body from the synthesization of other amino acids. Cysteine is also found in some foods that contain high levels of protein, including eggs, cheese and red meat.

What can happen if I take too much cysteine? Are there any interactions I should be aware of? What precautions should I take?

While virtually no research has been conducted on cysteine, preliminary studies on n-acetyl cysteine suggest that extremely large amounts may cause oxidative damage and/or nerve damage in animals. In addition, because cysteine is derived in large part from methionine, people need to have adequate amounts of methionine to prevent a cysteine deficiency from occurring. As of this writing, there are no well-known drug interactions with cysteine. As always, make sure to consult with a licensed health care provider before taking cysteine or any other dietary supplement or herbal remedy.

References

  • Salim AS. Sulfhydryl-containing agents in the treatment of gastric bleeding induced by nonsteroidal anti-inflammatory drugs. Can J Surg 1993;36:53-8.
  • Droge W, Eck HP, Gander H, et al. Modulation of lymphocyte functions and immune responses by cysteine and cysteine derivatives. Am J Med 1991;91(suppl 3C):140S-4S.
  • Droge W, Eck HP, Mihm S. HIV-induced cysteine deficiency and T-cell dysfunction - a rationale for treatment with N-acetyl cysteine. Immunol Today 1992;13:211-4.
  • Droge W. Cysteine and glutathione deficiency in AIDS patients: a rationale for the treatment with N-acetyl cysteine. Pharmacology 1993;46:61-5.
  • Kleinveld HA, Demacker PNM, Stalenhoef AFH. Failure of N-acetyl cysteine to reduce low-density lipoprotein oxidizability in healthy subjects. Eur J Clin Pharmacol 1992;639-42.

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