Synopsis

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

Quercetin is a flavonoid found in many fruits and vegetables, and it has been investigated for its potential role in supporting immune health and preventing the common cold. The rationale for its use is primarily based on scientific studies, although evidence remains preliminary and not definitive. Laboratory research has demonstrated that quercetin possesses antiviral, anti-inflammatory, and antioxidant properties, which could theoretically help in preventing viral infections such as the common cold. Some animal studies have shown that quercetin supplementation can reduce susceptibility to viral infections and decrease inflammation.

In humans, a few small clinical trials have explored quercetin’s effectiveness against upper respiratory tract infections (URTIs), including the common cold. One randomized, double-blind, placebo-controlled study found that quercetin supplementation (1,000 mg/day) modestly reduced the incidence and severity of URTIs in older adults. Another study in athletes suggested a reduction in URTI incidence following intensive exercise. However, other studies have found no significant effect. Overall, the clinical evidence is mixed and generally of low to moderate quality, with variations in study populations, dosages, and outcomes measured.

Major health authorities do not currently recommend quercetin for cold prevention due to insufficient high-quality evidence. While quercetin appears safe at typical supplemental doses, more robust clinical trials are needed to determine its true efficacy. Thus, its use for cold prevention is supported by emerging but not conclusive scientific evidence.

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