You may have heard about the potential benefits of trading in that morning cup of coffee for a healthy dose of green tea.
Or perhaps you’re wondering what green tea is, and how it differs from the black tea you serve iced or with milk. Both black and green tea are made from the same plant, but more of the original substances endure in the less-processed green form. A cup of green tea contains about 30 milligrams (mg) of caffeine, slightly less than black tea (50 mg) or coffee (85 mg).
Green tea is full of antioxidants, which may help ward off cancer and other chronic diseases. Now, scientific evidence suggests that green tea may also help with weight loss.
How might this work? Normally, after eating, your metabolic rate increases temporarily, burning extra calories, a process known as thermogenesis. Caffeine can cause a sustained increase in thermogenesis when taken in high doses (600 – 1,000 mg, equivalent to 7 to 12 cups of coffee). Now, a recent study suggests that a similar effect might occur with green tea, specifically green tea extract, a concentrated form available in capsules.
The study, conducted in Switzerland, involved ten healthy young men ranging from lean to mildly obese. All ate a typical Western diet, with 40 percent of calories coming from fat.
The subjects were split into three groups: one group took green tea extract capsules (which included, among other active ingredients, 50 milligrams caffeine) 3 times a day; another group took 50 milligrams of caffeine 3 times a day; and the final group took a placebo. Those taking green tea extract showed a 4 percent increase in thermogenesis. (This boost to thermogenesis was seen in a later study in rats, but the effect was much higher — 28 to 77 percent.) The subjects showed no signs of increased heart rate, which has been a serious side effect of some stimulant diet drugs. The caffeine-only and placebo groups burned fewer calories than the green-tea group, although actual weight loss was not measured.
Besides the thermogenesis effect, the green-tea extract group also showed an increase in fat breakdown. Researchers suspect that substances in green tea called polyphenols may change how the body uses norepinephrine, a brain chemical that controls the rate at which fat is burned.
But don’t trade in your treadmill for green tea capsules just yet. The thermogenic benefits that the human study cites are relatively small. If you’re consuming 1,800 calories a day, a 4 percent increase in thermogenesis means you’ll burn an extra 70 calories, (equivalent to one slice of bread). That’s just a seven-pound loss in a year.
too soon to tell
So, does this mean we’ll start seeing the use of green tea extract as a remedy for weight loss? “I hope not,” says Felicia Busch, R.D., a spokesperson for the American Dietetic Association. “One study of ten men living in Switzerland probably doesn’t fit the typical American woman trying to lose weight.” She also thinks the results are too limited to make any general recommendations. Mary Hardy, M.D., medical director of Cedars-Sinai Medical Center’s Integrative Medical Group in Los Angeles, says the study has a couple of problems. “First, it was only done in men, and men and women generally metabolize fat a little bit differently.”
drinking green tea vs. swallowing green tea extract capsules: there is a difference
It’s important to realize that drinking green tea is very different than taking it in capsule form. John Cardellina, Ph.D., vice president for botanical science at the Council for Responsible Nutrition in Washington, D.C., a supplement trade association, explains the use of extracts: “The advantage of taking the concentrated form is that it’s like drinking multiple cups of tea at one time. If you tried to drink six to ten cups of green tea at once, you’d get tired of it pretty quickly and spend a lot of time in the bathroom.” While green tea extract is available in stores, Cardellina says the research on its usefulness for weight loss is still very tentative: “We would need a large human trial, at the very least.” Also, the lack of standardization in the supplements industry means there are no strict controls on the composition of the extract, so you can’t always be sure of exactly what dose you’re getting.
drink it for the right reasons
All experts agree that while the jury is still out on green tea and weight loss, we do know enough about the other health benefits to recommend drinking it anyway. Hardy says that drinking the tea