Evidence supporting the use of: Cysteine
For the health condition: Influenza

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Synopsis

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

Cysteine, particularly in the form of the supplement N-acetylcysteine (NAC), has some scientific evidence supporting its use for influenza. NAC is a precursor to the antioxidant glutathione and has been studied for its ability to reduce oxidative stress and inflammation, which are key components of the body's response to viral infections like influenza.

The most notable clinical evidence comes from a double-blind, placebo-controlled study published in 1997 (De Flora et al., European Respiratory Journal), where 262 elderly subjects received either NAC or placebo for six months during flu season. Although both groups had similar rates of seroconversion to influenza virus infection, only 25% of the NAC group developed symptomatic influenza, compared to 79% in the placebo group, suggesting that NAC may reduce the severity of influenza symptoms rather than prevent infection entirely.

Additional in vitro and in vivo studies indicate that NAC can inhibit the replication of influenza virus and reduce inflammatory cytokine production, which may contribute to its beneficial effects. However, while the available evidence is promising, it is limited, and larger, more recent clinical trials are lacking. Thus, the scientific evidence supports a potential role for cysteine/NAC in reducing influenza severity, but it is not definitive enough for widespread clinical recommendation.

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Products containing Cysteine

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