The top researchers in the tea-health field (yes, it's a field -- a glorious one) propose tea as part of the approach to weight loss, heart health, and bone/muscle strength.Thomas Peter/Reuters
"It's really important to remember that tea is a plant," Jeffrey Blumberg told me at the 5th International Scientific Symposium on Tea and Human Health, located at the D.C. headquarters of the U.S. Department of Agriculture.
We don't typically think of tea as the type of green, leafy vegetable typically promoted by the USDA, but Blumberg, the meeting chair and a professor at the Friedman School of Nutrition Science at Tufts University, pointed out that the flavonoids extracted from tea leaves are similar to the beneficial phytochemicals found in fruits and vegetables. If we can't get Americans to eat the recommended daily amounts of fruits and vegetables, he suggests, why not let tea count as one or two servings?
The benefits may go beyond those gained from adding more plant food to your diet. The research presented at the symposium covered the gamut of health benefits attributed to tea -- from reduced risks of gastrointestinal cancers to improved mental acuity in older adults. And new studies suggest that tea could play an important role in three major public health issues:
In green tea, the combination of caffeine and catechins -- the stuff that gives it its bitterness and astringency -- may promote weight loss. Dr. Rick Hursel of Maastricht University in the Netherlands explained that in a meta-analysis of experimental trials, drinking green tea was associated with an increase in energy expenditure equivalent to burning about 100 extra calories in a 24-hour period. This, combined with an increase in blood fat oxidation, might explain why subjects in a related review lost an average of 2.9 pounds over a 12 week period.
These effects were slightly more prominent in subjects who weren't habitual caffeine users, and Asian subjects lost twice as much weight as Caucasian participants, suggesting that both lifestyle and genetic factors play a role in green tea's effects.
Hursel recommends 2-3 cups of green tea a day in those looking for weight loss benefits. Meanwhile, fried green tea ice cream remains best avoided.
If you can't stay away from fatty foods, Dr. Claudio Ferri of the University L'Aquila in Italy suggests following up your Big Mac with a cup of black tea. After observing tea's potent ability to dilate the arteries of lab rats, thus reducing their blood pressure, Ferri tested its effects in hypertensive human subjects. He found, somewhat incredibly, that tea consumption counteracted the meal's negative effects on blood pressure and arterial blood flow.
Blumberg jumped in, at that point, to clarify that the symposium was endorsing tea as part of a healthy diet.
But as Ferri pointed out, it can be difficult to get patients to give up their eating habits and switch over to his preferred Mediterranean diet. These results led him to conclude that preventing cardiovascular disease doesn't only have to be about sacrifice.
And, in a meta-analysis of over half a million normal individuals, drinking one cup of tea per day for a year was associated with a reduction in blood pressure equivalent to a 8-10 percent reduction in stroke risk.
Bone and Muscle Strength
From the Texas Tech University Health Science Center came a take on traditional Chinese medicine. Postmenopausal women -- who are at an extreme risk of osteoporosis -- were prescribed regimes of green tea and Tai Chi. Six months later, and with a high compliance rate, those who had consumed 4 to 6 cups of green tea daily, with or without the Tai Chi, had "improved markers for bone formation, reduced markers of inflammation, and increased muscle strength."
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Dr. Leslie Chen explained that while osteoporosis in incurable, the flavonoids and antioxidants found in green tea may work to mitigate its effects and reduce the risk for fractures. And even though it took a lot of tea, no adverse side effects were measured.
Further study is probably warranted in all of these areas. "But the bottom line is tea contains zero calories," said Blumberg. "And when you translate all of this data, a little increase in bone strength, a decrease in blood pressure, across a whole population, little changes make a big difference."