Evidence supporting the use of: L-cysteine
For the health condition: Acquired Immune Deficiency Syndrome

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Synopsis

Source of validity: Scientific
Rating (out of 5): 2

L-cysteine, a semi-essential amino acid, is a precursor to glutathione, a major intracellular antioxidant. Scientific interest in L-cysteine and its derivatives (notably N-acetylcysteine, NAC) for supporting patients with Acquired Immune Deficiency Syndrome (AIDS) originates from research indicating that glutathione levels are often depleted in people living with HIV/AIDS. Reduced glutathione is vital for immune function, antioxidant defenses, and cellular protection against oxidative stress—a prominent concern in HIV infection due to chronic inflammation and viral replication.

A number of clinical and preclinical studies have explored the effects of NAC supplementation (which acts as a cysteine donor) in HIV-positive individuals. Some studies suggest that NAC can increase glutathione levels, improve certain immune parameters (such as lymphocyte proliferation and function), and reduce HIV replication in vitro. However, the clinical benefits in terms of disease progression or survival are less clear, with most evidence limited to surrogate endpoints or small pilot trials. There is little direct evidence specifically for L-cysteine supplementation (as opposed to NAC), and large randomized controlled trials are lacking.

In summary, while there is a physiological rationale and some low-to-moderate quality evidence supporting the use of cysteine donors in HIV/AIDS, especially for restoring glutathione, robust clinical data on meaningful outcomes are insufficient. Thus, the evidence is rated as 2/5—promising but not definitive. L-cysteine is not a standard treatment for AIDS but may be considered as a supportive adjunct in some integrative or experimental protocols.

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