Abstract
Influenza and the common cold are acute infectious illnesses of the respiratory tract. Influenza is a severe, highly infectious disease caused by the influenza virus; when aggravated, it may become life-threatening. Both illnesses are highly infectious, making prevention very important. In basic studies, tea catechins have been found to inhibit influenza viral adsorption and suppress replication. Catechins are also effective against some cold viruses. In addition to catechins, green tea contains theanine and vitamin C, which enhance immunity against viral infection, suggesting green tea may prevent influenza and/or the common cold. Although the antiviral activity of tea components has been demonstrated, there has been limited clinical evidence to support their utility. Epidemiological studies suggest regular consumption of green tea decreases rates of influenza infection and some cold symptoms. Gargling with green tea catechin extracts and consumption of catechins and theanine may protect against the development of influenza. Further studies are needed to confirm their clinical efficacy.