November 7, 2005
Los Angeles Times/Health
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.
By 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.
Similar studies have linked green tea to protecting against a range of cancers — such as those of the lung, skin, esophagus, colon, bladder and possibly of the mammary glands.
EGCG isn't the only thing having an effect. Caffeine, for example, is probably providing the lion's share of protection in the case of the skin cancer experiments, and plays a big part in the lung ones, says green tea researcher Chung S. Yang, who chairs the chemical biology department at Rutgers University in New Jersey. (Sure you want to make that a decaf?)
The third line of evidence is the nitty-gritty one people care most about: What happens to humans when they drink tea? Such studies, because they're usually done in natural populations, not controlled groups, are tricky to interpret, partly because it's hard to measure how much tea people drink, and partly because tea-drinkers do a lot of other things too, both good and bad. For instance, it's common in China that men who drink a lot of tea also smoke a lot, Yang says.
The few human studies that have been done — primarily in Asia — have produced mixed results. But despite the complexities, some studies do look good, scientists say.
For example, in an article published in the International Journal of Cancer in 2003, scientists looked at the eating and drinking habits of more than 1,000 Chinese-, Japanese- and Filipino-American women in Los Angeles. They reported that women who drank green tea had a 43% lower risk of getting breast cancer compared with women who drank no tea. The more green tea the women drank, the lower their risk of breast cancer, according to the study.
Black tea showed no breast cancer protection, possibly because it has lower levels of EGCG and related chemical compounds.
"When I saw the results, I started drinking green tea," says author Anna H. Wu, professor of preventive medicine at USC.
Studies like these were enough to persuade Dr. Sin Hang Lee, a doctor in Connecticut, to start Dr. Lee's TeaForHealth, a company that sells organic green tea, and to petition the government in January 2004. Lee asked that the FDA allow green tea producers to label their products with a claim — known as a "qualified health claim" in FDA parlance — stating that drinking 40 ounces a day of green tea containing specific amounts of EGCG may reduce the risk of certain forms of cancer. Lee's FDA petition included stacks of green-tea studies.
A cautious FDA
When the FDA rejected Lee's petition, it denied outright any claim for some cancers and awarded decidedly limp qualified health claims for breast and prostate cancer.
Here, for breast cancer, is the most that the government would grant: "Two studies do not show that drinking green tea reduces the risk of breast cancer in women, but one weaker, more limited study suggests that drinking green tea may reduce this risk. Based on these studies, FDA concludes that it is highly unlikely that green tea reduces the risk of breast cancer."
That's hardly the choicest of messages for a seller to flaunt on the front of a box of tea.
"Qualified health claims need significant scientific evidence," says Kathy Ellwood, director of the Division of Nutrition and Labeling in the FDA's Center for Food Safety and Applied Nutrition. The FDA's need for caution, she says, compels it to consider animal and lab studies to be far less important than human research — and the scarcity of human green tea studies meant green tea could not get a cancer-fighting thumbs-up.
The FDA isn't alone in its skepticism. The American Cancer Society also concluded that more research is needed to show that green tea helps prevent cancer, and many other scientists concur.
Regardless of that, Terence Gilbert, a 61-year-old teacher in Topanga Canyon, still believes in green tea's power. Each morning, he pours a quart of not-quite-boiling water over loose leaves and allows the brew to steep for about 10 minutes. Then he sips it as he peruses the paper.
Gilbert began this morning ritual six years ago, after reading reports about green tea's health benefits. Since then, he says, he's been noticeably healthier.
"I'm with 200 kids a day, and I used to get three or four viruses a year," he says. "Now I get a virus only once every one to two years. I think my immune system is a lot stronger."
Despite the scientific uncertainty, it still makes sense to do as Gilbert does and drink green tea, says Jeffrey Blumberg, who directs antioxidant research at Tufts University's Human Nutrition Research Center on Aging.
The FDA, because it was responding only to Lee's petition, looked only at green tea's alleged cancer-fighting clout. It didn't consider heart disease, Alzheimer's or hypertension. "Human evidence for a cardiovascular benefit is much stronger than for cancer," Blumberg says.
Tea — sometimes black, sometimes green — has been shown to do a number of heart-healthy things. In human studies it has relaxed the artery walls, potentially lowering the risk of high blood pressure, heart attacks and stroke. It reduces a process that clogs arteries — the oxidation of LDL, or "bad" cholesterol — and lowers rates of atherosclerosis in animals. It increases levels of HDL, or "good" cholesterol.
Population studies also are intriguing: Last year, for instance, a Chinese study published in the Archives of Internal Medicine reported that people who drank green or oolong (black) tea had a 46% to 65% lower risk for high blood pressure.
As for fighting cancer, other human clinical studies are underway in the U.S. If these find evidence that green tea prevents cancer, tea producers say they will petition the FDA again.
If stronger evidence came to light, "we'd re-evaluate the evidence," the FDA's Elwood says. "Science evolves."
Rosie Mestel is a Times staff writer. Alice Lesch Kelly is a frequent contributor to the Health section.
BEGIN TEXT OF INFOBOX
Before a food manufacturer can claim on a package that a product has a health benefit, it must have permission from the Food and Drug Administration.
For years, the agency either approved or denied health claims. In 2003, however, the FDA began allowing "qualified" health claims — for when the agency believes there is some, but weaker evidence that a food or food component helps prevent a disease or condition.
Manufacturers who put a health claim on a product must post the FDA's position in its entirety (not just the favorable stuff).
Following is a partial list of foods and ingredients that the FDA has decided merit a health claim, a qualified health claim or no claim at all:
Health claims the FDA allows:
• Calcium helps women maintain good bone health and reduce their risk of osteoporosis later in life.
• Fruits and vegetables, and nutrients from these diets such as vitamin C, vitamin A and dietary fiber, reduce the risk of some types of cancer.
Qualified health claims the FDA allows:
• Selenium, which is found in beef and tuna, may reduce the risk of certain cancers.
• Eating 1.5 ounces of nuts such as almonds, hazelnuts and peanuts every day as part of a diet low in saturated fat and cholesterol could reduce the risk of heart disease.
• Green tea may help prevent breast cancer and prostate cancer, but the link is highly unlikely.
Claims the FDA denied:
• Green tea reduces the risk of gastric, ovarian and lung cancer.
• Chromium picolinate reduces cardiovascular disease in Type 2 diabetes.
— Daniel Costello
BEGIN TEXT OF INFOBOX
Scientists may still be figuring out if and how green tea protects us from disease, but there are things you can do to improve your brew. Here's how to get the most out of green tea:
• Don't use boiling water: It can make green tea taste bitter. Cool boiled water for one to three minutes before adding leaves.
• Allow green tea to brew for several minutes — longer than for black tea. Loose tea needs more time than tea bags.
• Antioxidants degrade over time, so if you make iced green tea, drink it within 24 hours.
• Steer clear of green tea supplements. They may not provide the same benefits: A 2005 study found that mega-doses of green tea extract actually helped tumors grow.
• Check the label if you buy bottled green tea drinks. They may contain mainly sugar and not much green tea.
— Alice Lesch Kelly