Something caught my eye the other day while reading a handbook of the Urasenke school of Japanese tea ceremony. I wasn't expecting to find it in this rather scholarly type book dealing with history, art and philosophy of the Japanese tea ceremony. There in the chapter, Tea and Health among the many health benefits listed was "(prevention of) infection by the influenza virus."
It kind of startled me. I had never heard of tea helping in warding off flu. I knew of many other health claims like preventing certain types of cancer, enhancing metabolism, controlling cholesterol and the more faddish losing weight, anti-aging, etc. But keeping influenza virus at bay? No, sir, that I did not know.
Chemical structure of green tea catechins
Given the once in a multi-generation pandemic at hand, I immediately started digging around. I was happily surprised to find quite a bit of research had been done on the subject. (The grandmasters of Japanese tea ceremony were not just pulling it out of thin air.) Alas a lot of it was dense scientific research requiring academic credentials to access. However, whatever we could parse through the abstracts looked quite compelling.
For instance, during the winter of 2008-2009 there was a study done in Japan (the full paper is available here) of influenza among school children (age 6-13 years old) and green tea consumption. It concluded that consumption of 1-5 cups of green tea per day did reduce the incidence of influenza. Notably, the study was done in Kikugawa city which is located in a tea growing region of Japan with strong local habits of green tea consumption.
Another 2018 study by Japanese scientists, "Effect of Tea Catechins on Influenza Infection and the Common Cold with a Focus on Epidemiological/Clinical Studies", concluded that "although the number of clinical/epidemiological studies on tea catechins against influenza and the common cold are limited, the present studies suggest the possibility of preventive effects on influenza and common cold." It also suggested that gargling with tea lowered risks of influenza infection. Interestingly, the authors themselves raised a question as to how that is possible given that most of the virus invades from the nasal cavity.
In 2018 South Korean scientists studied the anti-viral efficacy of green tea extract against human influenza virus or H1N1. They found the catechin found in tea, "epigallocatechin 3-gallate" exhibits a strong anti-viral property and recommended the use of green tea extract to make a more "safer" anti-viral product like hand sanitizer. The researchers note their study was to address concerns about making hand sanitizers safer and more environmentally friendly.
You can access above study here.
These studies - and there are more - are very interesting. They were conducted in the wake of the SARs and MERs outbreaks. We are not trying to suggest that drinking green tea will keep you safe from COVID-19. Admittedly, a lot of research still needs to be done in the field. But who can discount the power of suggestion or the placebo effect? I am making myself another bowl of matcha right now!