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We've heard it for years: Green tea is good for us. But without more evidence, the FDA won't let it be called a cancer fighter.

November 07, 2005|Alice Lesch Kelly and Rosie Mestel | Special to The Times

TEA, to China's 18th century Emperor Chien Lung, was more than a whistle-wetting pick-me-up: It was "that precious drink which drives away the five causes of sorrow."

Western businesses are banking on our buying into Chien Lung's sentiments. In addition to selling a cornucopia of loose green teas, they have distilled the brew's essence and added it to health bars, supplements, diet aids, gum, soft drinks and skin creams -- even, in Asia, to Kit Kat candy bars.

Green tea is good for us: That mantra has been chanted in the West since the early 1990s, when studies reported that the infusion, sipped for centuries in China and Japan, appeared to help fight off cancers when drunk by lab mice or rubbed on their skin. Enthusiasm intensified after other studies revealed that green tea contained certain chemicals with cancer-fighting clout. Scientists rolled up their sleeves to figure out how it works.

Today, green tea imports are soaring.

"Ten years ago, 3% of imported tea was green tea. Now it's 12%," says Joe Simrany, president of the Tea Assn. of the U.S.A. "Most of that increase is based on the perceived health benefits of green tea."

So confident was one doctor-turned-green tea businessman that in 2004 he decided the time was ripe to petition the Food and Drug Administration to permit green teas to sport cancer-fighting health claims on their packages.

The FDA's response: tepid. At best.

In June, the agency ruled that there was "no credible evidence" green tea fights cancers of the stomach, lung, colon, esophagus, pancreas or ovary. The agency acknowledged that the evidence for tea fighting breast or prostate cancer was somewhat better, although it also said the link was "highly unlikely" because the evidence on humans wasn't conclusive enough.

So what's the deal? Is green tea good for us or not? How can scores of scientific papers hold so little sway (to say nothing of all those mice purportedly whisked from the jaws of death through the intercession of tea)?

Is it time for us to abandon green tea for the healing power of fish oil or pomegranate pills?

Scientists say that despite the unanswered questions green tea still shows promise, not only as a potential cancer-protector but also against other health threats such as cardiovascular disease, and possibly Alzheimer's. But they also are mindful that many a cell in a dish has been vanquished, and many a mouse cured of cancer, from therapies that don't ultimately pan out in human populations.

"You can build your case in cell studies and animal studies but ultimately you have to do it in humans or you can't make a case that it works," says Balz Frei, a professor of biochemistry at Oregon State University.

Bottom line: Until carefully done studies in people show convincing and consistent evidence of green tea's clout, scientists can't say for sure if the drink will live up to the hype that continues to swirl around it.

What makes it different

Green tea is made from the dried leaves of Camellia sinensis, an evergreen shrub native to Asia. Nobody knows who invented the drink. One legend goes that Buddha happened upon the beverage after tea leaves fell into his cup while he was meditating outdoors. He found the contamination tasty.

Cultivated for thousands of years in China and Japan, the plant is harvested and treated in different ways to produce green tea or black tea.

Green tea is made by steaming the crushed leaves shortly after harvest, destroying enzymes so that chemicals in the tea aren't oxidized very much.

Leaves used for black tea ferment for days before they're heated, causing the leaves to blacken and many chemical changes to occur within them. (Eighty percent of the tea consumed in the world is black tea.)

Those processing differences may be medicinally important. Both types of tea are abundant in certain antioxidant chemicals called flavonoids, which obstruct the action of cell-damaging free radicals. (Ounce for ounce, tea has more antioxidant clout than broccoli or Brussels sprouts.) But green tea, because it doesn't ferment as long, has much higher levels of a group of flavonoids called catechins. A particularly potent catechin -- with a mouthful of a name, epigallocatechin gallate, or EGCG -- is three to four times more abundant in green tea than black.

Scientists cite three lines of green tea anti-cancer evidence.

First, there are test-tube studies. Green tea's flavonoids interfere with cancer-related biochemical reactions: They may cause cancer cells to grow sluggishly, cease dividing or even self-destruct. Flavonoids also impede formation of carcinogens known as heterocyclic amines (the bad-for-you chemicals that form when meat is broiled).

Then there are studies in rodents. In one fairly typical study, mice were injected with a tobacco carcinogen that caused them to develop lung tumors months later. Some of the mice got green tea to drink, and others did not. The tea-drinking mice got fewer tumors.

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