Researchers at the Brigham and Women's Hospital in Boston recently found evidence that tea may even jump-start the immune system to fend off attacks from bacteria. Drinking a 20-ounce cup of tea every day for two weeks doubled the immune system's output of the infection-fighting substance interferon gamma, priming the body for the battle against infectious bugs. And another study released in April from the National Academy of Sciences shows a chemical called L-theanine, a substance found in black, green and oolong tea, helps stimulate an immune blood cell called the gamma-delta T-cell.
Now researchers at the University of Arizona's College of Public Health have been awarded two grants totaling $3.12 million to study the effects of tea on disease prevention, through the Southeastern Arizona Tea Studies office, established in 1999.
One study will look at preventing lung cancer among former heavy smokers, and the other focuses on minimizing oxidative stress that, when enhanced, may contribute to lung cancer, cardiovascular diseases, diabetes and other chronic diseases.
What's interesting is that the second of the two four-year studies is funded by a $1.26 million grant from the Department of Defense. The Pentagon wants to look at the effects of green and black tea on minimizing oxidative stress among battle-weary soldiers training for the front line.
"What we are measuring for the Defense Department is damage to the DNA related to oxidative stress," says Dr. Iman Hakim, director of the UA's Division of Health Promotion Sciences and the principle investigator of the studies.
"The Army, in their environment and the way they train, might be much more prone to this stress, so if we can find a way to decrease oxidative stress, it would be a way to protect them from further health problems."
It's not odd the Defense Department would fund such a project, since the Pentagon actually posts a list of health-related projects they wish to fund each year so researchers can submit grant proposals.
What's even more interesting is that while 80 percent of the world drinks black tea, tea is, well, tea. It all comes from the same botanical plant; it's just processed differently, creating the green, black or oolong types familiar to most steepers.
How teas are processed, according to Dr. Hakim, causes chemical changes, which in turn cause a difference in antioxidants they contain. While green tea has more simple catechins, black tea processing results in more complicated theaflavins and thearubigins antioxidants. Before your head explodes reading this, doctors are not sure if one type is better then the other.
The second study, funded by a $1.86 million award from the National Institutes of Health, aims to determine whether drinking green tea can prevent lung cancer in former heavy smokers. Smoking enhances oxidative stress and may lead to tissue damage, even after people cease smoking. This study will use green tea intervention among former smokers with more than or equal to 40 "pack-years" of smoking history.
Hakim notes that subjects will be randomly assigned to consume daily for six months either a standard green tea beverage, a green tea extract in capsule form, or a placebo.
Still, research results on the health benefits of tea remains contradictory and have not conclusively shown that tea will prevent cancers, though preliminary results indicate potential benefits.
Tea drinking has been a tradition in Japan and China, known to date back more than 1,000 years. Still, one only need look at the millions of tea drinkers in China, where recent problems like SARS have easily spread, to wonder if these benefits are for real.
"Most of the studies that were done are animal studies, so to take these studies to human studies É is the challenge right now," says Hakim. "We will know in four years."