After studying green tea at a biochemical level, a particular compound from Camelia Sinensis was discovered to be capable of suppressing the influenza virus and its associated symptoms.

Known as a catechin, the compound was found to exhibit characteristics that demonstrated antiviral activity.

Catechins are also active against other pathogens in the respiratory tract, which is a common infection site for influenza. They directly prevent infection by binding to glycoprotein spikes on the surface of viruses. This action renders the virus incapable of adsorption or binding to the receptors of host cells in the respiratory tract by destroying the protective mucus coating that lines it, therefore, deterring infection.

The most prominent catechin compound is epigallocatechin-3-gallate (EGCG), which was the main focus of Mikio Nakayama’s research against influenza viruses. Nakayama found that EGCG could inhibit agglutination (clumping effects) in two types of viruses, including Influenza A (the main cause of flu epidemics).

This prevents them from successfully attaching to host cells. Other catechins, such as Epigallocatechin (EGC) and Epicatechin-3-O-gallate (ECG), were used in similar experiments and displayed some capacity for anti-viral activity, but EGCG was found to be the most effective.

Alongside understanding the biochemistry behind green tea, a few studies provide insight into the use of green tea as a protective measure against influenza within communities.

Some studies examined the effects of gargling green tea in the elderly population, while others concentrated on its health benefits in children and high school students. In one study, gargling green tea or its ingredients was associated with a lower likelihood of infection than gargling water or placebo alternatives. In another study, 124 elderly volunteers who gargled catechin extract exhibited similar therapeutic effects, while 200 healthcare workers in a separate investigation demonstrated the same outcome and were protected against the Influenza A virus.

Thus, it is evident that EGCG and other tea catechins have been associated with protection against the influenza virus in humans.

Despite the potential application of tea catechins in antiviral protection, existing evidence does not verify green tea as an alternative to medical treatments. Annual vaccinations remain a viable defence option against the flu bug considering the high viral mutation rates that lead to re-emerging outbreaks of influenza and related pandemics, such as the 2009 Swine Flu outbreak.