Dr Stephen Hsu, a researcher at the Medical College of Georgia's School of Dentistry, suspected that there may be a link between green tea consumption and autoimmunity after noting that dry mouth, or xerostamina, an autoimmune disorder suffered by around 30 percent of elderly Americans, occurs in only one to two percent of Chinese people in the same age group.
Green tea is a common component of the typical Chinese diet.
Autoimmune disorders occur when the immune system starts to attack the body's own tissues. They may be triggered by other health conditions, such as type 1 diabetes, rheumatoid arthritis, lupus and Sjogren's disease, and can have debilitating and even life threatening effects.
Dr Hsu will present the findings of his latest investigations, involving green tea's role in producing autoantigens, at the Arthritis research Conference in Atlanta this weekend.
Autoantigens are molecules that have useful functions, but changes in their amount or location can trigger an immune response.
The inquiry was driven by existing evidence that a polyphenol called EGCG suppresses inflammation, caused when the immune system mounts a defense to a real or perceived enemy.
"If EGCG suppresses inflammation, it should affect the magnitude of the autoimmune response, possibly by suppressing autoantigens," said Dr Hsu.
By studying cells in salivary glands and skin tissue, he saw that cells exposed to green tea showed RNA and protein levels indicating autoantigen levels were suppressed in these normal cells, but not in tumor cells.
According to the researcher, the upshot of this is that the immune system now has considerably fewer targets to potentially attack, greatly reducing the risk of autoimmune disease.
Dr Hsu, who said he was "shocked" by the findings, has now expanded the study to mice models.
Green tea has been shown to deliver benefits for a wide range of conditions, from oral cancer to wrinkles, thanks to the presence of polyphenols that help eliminate DNA-damaging free radicals. While the polyphenols destroy cancer cells for destruction, a green tea-induced protein called p57 is said to protect healthy cells.