Synopsis

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

Quercetin, a flavonoid found in many fruits and vegetables, has gained attention for its potential antiviral properties, including possible benefits against influenza. Several preclinical studies (in vitro and animal models) have demonstrated that quercetin can inhibit the replication of various influenza virus strains. The proposed mechanisms include blocking viral entry, interfering with viral replication, and modulating the immune response to reduce inflammation and oxidative stress. For example, a 2016 study published in Viruses showed that quercetin inhibited influenza A virus replication in cell cultures and mice, leading to reduced viral load and improved survival rates.

However, clinical evidence in humans is limited. There are very few randomized controlled trials (RCTs) investigating quercetin's efficacy for treating or preventing influenza in humans. Some small studies suggest that quercetin supplementation may reduce the incidence or severity of upper respiratory tract infections, but these studies often include multiple viruses (not only influenza) and sometimes involve quercetin in combination with other compounds (like vitamin C or bromelain). No large, high-quality RCTs have conclusively proven quercetin’s benefit specifically for influenza.

In summary, while there is a scientific rationale and promising preclinical data for quercetin's use in influenza, the current level of evidence in humans is low. More robust clinical trials are needed to establish its effectiveness and safety for this specific application.

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