New research has found more evidence of green tea’s flu-fighting powers—just in case the weight loss, heart health, and cancer-preventing benefits haven’t convinced you to start sipping already.
Japanese researchers gave one group of health care workers pills containing 378 mg of catechins (the equivalent of 2 cups of green tea) and 210 mg of theanine (the equivalent of 4 cups). They took six capsules every day for 5 months. Yes, that’s a lot of tea supplements—but the results were striking: Only 4 percent of the green tea group came down with the flu, compared to 13 percent of the control group.
“Catechins bind to the influenza virus,” explains Hiroshi Yamada, M.D., Ph.D., and coauthor of the study. “This prevents the virus from being absorbed by your healthy cells and stops it from maturing.” Theanine is also believed to enhance immunity but researchers are still figuring out how.
You don’t need to down gallons a day, though—Dr. Yamada says you can see health benefits with just two cups. So we asked him: How do we make the most from our brew?
1) Accept no substitutes

Though other types of tea have comparable levels of theanine, green tea has more catechins, making it optimal for flu prevention, explains Dr. Yamada. If you don’t like green tea, white tea and oolong tea are good backup options.
2) Buy loose leaves
Experts say that, in general, loose tea leaves have higher concentrations of the flu-fighting compounds than bagged tea.
3) Brew hot, brew long
Brewing your tea for a longer time and at a higher temperature will increase the concentration of catechins, though the exact levels are difficult to measure, explains Dr. Yamada. Make sure to brew for at least 1 to 2 minutes at 175 degrees (extremely hot), or 3 to 5 minutes at 140 degrees (hot but drinkable).
If you really hate tea, consider a green tea supplement such as this green tea complex, which has approximately the same catechin levels as one cup of tea. A University of California study found that green tea supplements retain many of the positive health effects of drinking tea.