Consuming tea catechins, a polyphenol found in tea that holds antioxidant properties, or simply gargling tea, demonstrated protective effects against flu and other upper respiratory tract infections in several clinical trials covered in a review appearing in the European Journal of Nutrition.
 
The authors of the review looked at four prospective cohort studies with a sum population of 3,748 participants, who were either monitored for their tea consumption or instructed to gargle tea, in order to evaluate any possible impact that doing so would have on incidences of flu and/or other upper respiratory tract infections.
 
“Catechins, which are found in tea leaves (Camellia sinensis) are compound mixtures classified as flavanols and include [EGCg], which has anti-viral effects in vitro. Because EGCg acts on a viral membrane protein at an early stage of infection by inhibiting absorption, penetration, and membrane fusion, and is present in a common beverage that is available worldwide, it represents an easily accessible [non-pharmaceutical intervention] against viral respiratory infections,” the authors of the review said. They noted that previous meta-analyses suggest that gargling tea appears to have preventive effects against flu infection, reducing rates by as much as 32.1% in healthy populations, though tea gargling isn’t a common practice.
 
All of the flu cases in the study were confirmed using a definitive diagnosis achieved through lab tests, while for other upper respiratory tract infections, the studies relied on subjective reports of clinical symptoms, including both flu-like symptoms and other acute respiratory tract infection symptoms.
 
The authors said that the review put forward represents the first comprehensive analysis revealing significant protective benefits of tea gargling and catechin consumption against certain viral infections. “The strength of our study lies in the complete adherence to systematic review methods, including the two-tiered screening process of publication titles and abstracts by independent researchers, evaluation of the quality of each study, evaluation of risk of bias, and no limitation regarding the language used in the publications.”
 
Through the analysis, the authors found that consuming catechin-containing drinks or catechin-containing capsules, the study population saw a reduction of both flu and other upper respiratory tract infections of 32%, while tea gargling was linked to a 17% reduction in risk. However, all studies used in the review were observational in nature, and the authors couldn’t make a definitive conclusion regarding the mechanism of action by which catechins offered RTI protection.