What does it do? Cysteine is a
nonessential amino acid
(protein building block). Cysteine is one of the few amino acids that contains sulfur.
This allows cysteine to bond in a special way and maintain the structure of proteins in
the body. Cysteine is a component of the antioxidant glutathione. The body also uses
cysteine to produce taurine,
another amino acid.
Cysteine is occasionally converted
into glucose and used 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.1 In addition, cysteine may play an important role in the communication
between immune
system cells.2 Cysteine is rarely used as a dietary supplement. N-acetyl cysteine (NAC),
which contains cysteine, is more commonly used as a supplement.
Where is it found? The body can synthesize cysteine from methionine and other
building blocks. Cysteine, the amino acid from which NAC is derived, is found in most
high-protein foods. Refer to N-acetyl cysteine for corresponding health concerns.
| Who is likely to be
deficient? According to
several studies, blood levels of cysteine and glutathione are low in individuals infected
with HIV.3
4 5 Cysteine has a role in the proper function of the immune system, so a deficiency
of this amino acid may either contribute to or result from immune suppression associated
with HIV. How much is
usually taken? Most people
do not need to supplement cysteine. Almost nothing is known about appropriate supplemental
levels, in part because almost all clinical research has been done with N-acetyl cysteine
and not cysteine itself. Refer to the section on N-acetyl cysteine (NAC) for information about that
variation of the cysteine molecule. |
 |
Product Recommendations |
- L-Cysteine
- 60 Cap.
-
|
|
| Are there any side
effects or interactions? No
consistent adverse effects of NAC have been reported in humans. One small study found that
daily amounts of 1.2 grams or more could lead to oxidative damage.6 Extremely
large amounts of cysteine, the amino acid NAC is derived from, may be toxic to nerve cells
in rats.7 |
 - Ask the Expert about Amino
Acids Supplements (click)
|
Adequate amounts of methionine are needed
in the diet, as the precursor to cysteine, to prevent cysteine deficiency.
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- References:
- 1. Salim AS. Sulfhydryl-containing agents in the
treatment of gastric bleeding induced by nonsteroidal anti-inflammatory drugs. Can J
Surgery 1993;36:53–58.
2. Droge W, Eck HP, Gander H, Mihm S. Modulation of lymphocyte functions and immune
responses by cysteine and cysteine derivatives. Am J Med 1991;91(suppl
3C):140S–44S.
3. Eck HP, Gander H, Hartmann M, et al. Low concentrations of acid-soluble thiol
(cysteine) in the blood plasma of HIV-1 infected patients. Biol Chem Hoppe Seyler
1989;370:101–8.
4. Droge W, Eck HP, Mihm S. HIV-induced cysteine deficiency and T-cell dysfunction—a
rationale for treatment with N-acetylcysteine. Immunol Today 1992;13:211–14.
5. Droge W. Cysteine and glutathione deficiency in AIDS patients: A rationale for the
treatment with N-acetyl-cysteine. Pharmacol 1993;46:61–65.
6. Kleinveld HA, Demacker PNM, Stalenhoef AFH. Failure of N-acetylcysteine to reduce
low-density lipoprotein oxidizability in healthy subjects. Eur J Clin Pharmacol
1992;639–42.
7. Olney JW, Ho O-L. Brain damage in infant mice following oral intake of glutamate,
aspartate or cysteine. Nature 1970;227:609–10 [letter].
