New evidence suggests that drinking the increasingly popular green tea may provide some relief to allergy sufferers.
Researchers in Japan identified a compound in green tea that, in laboratory tests, blocks a key cell receptor involved in producing an allergic response. The compound, methylated epigallocatechin gallate (EGCG), may have a similar effect in humans, they said.
The study will be published in the 9 October issue of the Journal of Agricultural and Food Chemistry, the American Chemical Society publication.
Although similar compounds in green tea have previously been shown to be anti-allergenic, this particular compound appears to be the most potent, the researchers said.
"Green tea appears to be a promising source for effective anti-allergenic agents," said Hirofumi Tachibana, the study's chief investigator and an associate professor of chemistry at Kyushu University in Fukuoka, Japan. "If you have allergies, you should consider drinking it."
People have long been drinking tea to fight the sneezing, coughing and watery eyes that are characteristic of colds and allergies. The new study adds to a small but growing body of scientific evidence from both cell and animal studies that it may actually work, particularly green tea.
No one has proven, however, that anti-allergenic compounds found so far have a therapeutic effect in humans who ingest green tea. But if it works, the brew may be useful against a wide range of allergens, including pollen, dust, pet dander and certain chemicals, Tachibana said. There are currently 50 million people in the US suffering from allergies however the researchers noted that further studies are needed.
EGCG is one of the most abundant and biologically active antioxidants found in tea. It is believed to be responsible for tea's beneficial health effects. The compound is found in higher concentrations in green tea, the least processed of teas, than in black and oolong varieties.
Previous studies have shown that EGCG fights allergic reactions in rodents that were given the compound orally, but researchers are just beginning to understand how it might work.
It now appears that the compound works by blocking the production of histamine and immunoglobulin E (IgE), two compounds in the body that are chiefly involved in triggering and sustaining allergic reactions, Tachibana explained.
The current study shows for the first time that a methylated form of EGCG can block the IgE receptor, which is a key receptor involved in an allergic response. The effect was demonstrated using human basophils, blood cells that release histamine.
Methylated EGCG appears to elicit a stronger anti-allergenic response than normal EGCG, making it the strongest anti-allergen compound found in tea, according to the researchers.
Although promising against allergies no one knows how much green tea is needed to have a therapeutic effect, or which green tea varieties work best, the researchers added. They are currently looking for additional anti-allergenic compounds in the tea.
Green tea has been called the second-most consumed beverage in the world, behind water. Already very popular in Japan, it has a growing following in the United States, where black tea has traditionally been favoured. Tachibana's study adds to an expanding list of the potential health benefits offered by green tea. In addition to allergies, it is reported to fight cancer, cardiovascular disease, arthritis and tooth decay.
Funding for the study was provided in part by grants from the Program for Promotion of Basic Research Activities for Innovative Biosciences (PROBRAIN).