Evidence supporting the use of: L-cysteine
For the health condition: Heavy Metal Poisoning

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Synopsis

Source of validity: Scientific
Rating (out of 5): 3

L-cysteine is an amino acid that plays a role in the synthesis of glutathione, a major intracellular antioxidant involved in detoxification processes, including the conjugation and elimination of heavy metals such as mercury, lead, and cadmium. Scientific interest in L-cysteine and its derivatives (most notably N-acetylcysteine, or NAC) largely stems from their ability to replenish glutathione levels and directly chelate certain metals due to their sulfhydryl (-SH) groups, which can bind to metal ions. Preclinical studies, including animal models, have demonstrated that both L-cysteine and NAC can reduce the toxicity of various heavy metals, enhance their excretion, and mitigate oxidative stress induced by metal exposure. Some small human studies and case reports support the use of NAC as an adjunct in heavy metal poisoning, especially when conventional chelation agents are not available or as supportive therapy. However, L-cysteine itself is less commonly used in clinical protocols compared to NAC or standard chelators like dimercaprol or EDTA. The strength of the evidence is moderate, with most data derived from animal studies and limited human trials; thus, L-cysteine is considered a scientifically plausible but not primary intervention for heavy metal poisoning. Its main role is supportive—helping the body’s own detoxification pathways. More rigorous clinical trials are needed to clarify its efficacy and safety in this context.

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