Both the green and the black fermented tea contain a so-called antigen by the name alkylamine plus its precursor L-theanine. The same antigen is also present in certain bacteria, parasites, fungi, and in tumour cells.
By contrast, coffee contains neither alkylamine nor L-theanine.
When we drink tea, our body is presented to alkylamine. This causes our immune defence to become familiar with the substance so that it can react to it much faster and more effectively should it appear in our body in the form of a cancer or an infection with a microorganism that contains this very antigen.
A group of researchers at Harvard and New Hampshire has studied how the gamma-delta T cells react to alkylamine. The gamma-delta T cells are the body's "front-line soldiers" in combatting infections.
In the study, the gamma-delta T cells from humans were exposed to alkylamine. Then, they were exposed to a bacterium in order to imitate an infection. It turned out that the cells who had previously been exposed to alkylamine were 10 times more effective in fighting off the infection than the cells who had not been exposed to this antigen.
After this, the trial subjects were asked to drink either five cups of black tea or five cups of coffee a day for up to four weeks. After two weeks, the T cells of the tea drinkers were already capable of producing anti-infectious substances; this, however, was not the case in the coffee drinkers.
Reference:
Kamath AB., et al. Antigens in tea-beverage prime human V 2V 2 T cells in vitro and in vivo for memory and nonmemory antibacterial cytokine responses. PNAS (2003) 10.1073/pnas.1035603100
