Does tea ward off disease?

Tea is in. The average American drinks some 155 cups a year. That makes tea the country's fourth most popular beverage, after water, soft drinks, and coffee. And green tea extracts are the fastest-growing dietary supplements.

There's no doubt that tea is an invigorating drink--you can probably credit its caffeine for that (tea has about half the caffeine of coffee). And the national waistline would be far better off if we replaced some of that soda with tea (provided we sipped it with little or no sugar).

But does tea lower the risk of cancer, heart disease, and obesity, as some companies claim? Let's check the tea leaves.

HEART DISEASE

"Tea drinking is associated with improved cardiovascular health," says the Tea Association's Web site. Yet the Food and Drug Administration concluded last year that "there is no credible scientific evidence" that green tea can reduce the risk of heart disease. (The evidence for black tea isn't good, either.)

Who's right?

"It's confusing when you look across all the epidemiological studies," says tea researcher David Maron of the Vanderbilt Heart Institute in Nashville, Tennessee. "Some studies find that drinking tea is linked to less cardiovascular disease, some do not, and some actually find an increased risk from drinking tea."

Clearly, the Tea Association isn't confused. According to the industry group's Web site, a University of North Carolina analysis of more than a dozen published studies "found an average estimated 11 percent lower rate of heart attacks among study participants who drank three or more cups of tea per day." (1)

The tea folks fail to disclose that the studies' results were so contradictory that, statistically, the 11 percent reduction was no different from a zero reduction. (2)

But what if three cups of tea a day aren't enough? Apparently, neither are five cups, at least not in the most recent large studies that looked at the health of tea drinkers.

Among 40,000 healthy middle-aged and older Japanese men and women, those who drank five or more cups of green tea a day were just as likely to die of heart disease during an 11-year period as those who drank less than one cup a day. (3)

Unfortunately, clinical studies--which give people tea or a placebo and wait to see what happens--are scarce.

"There really is not a lot of evidence from good clinical trials," notes Maron. "None have looked at whether drinking tea or taking tea extracts prevents heart attacks or strokes, and only a few have looked at whether it lessens any risk factors."

Last year, the FDA reviewed the evidence after a Japanese company asked for permission to say on its labels that its green tea could lower the risk of heart disease. In the seven good clinical studies submitted by the company, green tea or green tea extracts did nothing to lower cholesterol or blood pressure. The FDA denied the company's petition.

However, a 2003 clinical study found that 114 men and women who took a tea extract called Teaflavin every day for three months ended up with LDL ("bad") cholesterol levels that were 15 percent lower than those of 114 similar people who were given a placebo. (4)

But the Teaflavin takers were getting the equivalent of 35 cups of tea a day. (Teaflavin combines the antioxidants theaflavin from black tea and catechins from green tea.)

"It's ridiculous to try to lower cholesterol levels by drinking tea, because you would have to drink dozens of cups every day," says David Maron, who conducted the study for Teaflavin's manufacturer.

"If someone can't lower cholesterol by diet--or can't or doesn't want to use prescription statin drugs--then I would say he or she could try this extract to see if it helps."

(A month's supply of Teaflavin, available from www.teaflavin.com, costs around $40.)

Bottom line: Drinking tea doesn't appear to prevent heart disease. While one brand of tea extract lowered LDL ("bad") cholesterol in one published study, that's not enough to conclude that it works.

Celestial Intervention

Say you're Celestial Seasonings and you want consumers to believe that tea helps prevent heart disease, but the FDA says there's "no credible scientific evidence."

Not to worry. Make it look like another government agency is endorsing your claim.

How? "Partner" with the renowned National Heart, Lung, and Blood Institute (NHLBI) on its "The Heart Truth" campaign. Put up your dollars, then proclaim publicly what the FDA would never let you say.

Issue a press release about how your "Partnership Highlights Benefits of Tea Consumption in Helping Reduce Risk of Cardiovascular Disease."

In it, say that "drinking more tea can help promote heart health." Then let the NHLBI post the release on its Web site (www.nhlbi.nih.gov/ health/hearttruth/press/nhlbi_ht_ celestial.pdf).

NHLBI communications director Terry Long says that consumers won't assume that the company's claims have been approved by the institute.

"We're not a regulatory agency and we're not trying to counter any message from another federal agency," she says.

"We're in the business of educating women about heart disease. Celestial Seasonings has been a part of that for a long time, and we don't weigh in on the issue of tea and heart disease."

Apparently, the NHLBI lets Celestial Seasonings do that.

Cancer

In the 1990s, tea seemed like a miracle cancer-fighter.

"There's no agent in the literature that has shown such remarkable effects in so many animal systems," Hasan Mukhtar of Case Western Reserve University in Cleveland told Nutrition Action in 1994.

He was hardly exaggerating. When researchers give animals carcinogens, tea extracts reduce the number of tumors in the breast, colon, prostate, pancreas, skin, lung, esophagus, and small intestine.

But what was missing 10 years ago is still missing: evidence that tea also prevents cancer in people.

"While most of the animal studies that have been reported have been positive, the epidemiological data are not clear in finding a benefit for tea on cancer in humans," says researcher Joshua Lambert of Rutgers University in New Jersey.

For example, in a study of 40,000 healthy middle-aged and older Japanese men and women, those who drank five or more cups of green tea a day were just as likely to die of cancer during an 11-year period as those who drank less than one cup a day. (3) As for specific cancers:

* Colon. In 28 studies on three continents, people who drank the most black or green tea were just as likely to get colon cancer as those who drank the least. (5)

* Prostate. In the most recent study, which looked at 19,000 Japanese men, those who drank five or more cups of green tea a day were just as likely to die of prostate cancer as those who drank less than one cup a day. (6)

"The epidemiological evidence for black or green tea protecting against prostate cancer is not very strong," says Anna Wu of UCLA.

In 2005, Canadian researchers gave 500 milligrams a day of green tea extract to 15 men with advanced prostate cancer for two to six months. All of their cancers worsened. (7)

And in an unpublished study from the National Cancer Institute, only one of 42 prostate cancer patients who drank four cups of green tea every day for four months showed even a short-lived improvement.

* Breast. "Studies show that drinking black tea has no effect on breast cancer," says Wu.

In 13 studies in eight countries involving more than 160,000 women, those who drank the most black tea, usually four or more cups a day, were just as likely to be diagnosed with breast cancer as those who drank the least. (8)

For green tea, "the evidence isn't very strong, either," says Wu. In three studies that tracked nearly 70,000 Japanese women for seven to 24 years, those who drank at least five cups of green tea daily were just as likely to be diagnosed with breast cancer as those who drank little or none. (8)

But, says Wu, "we need additional human studies that carefully document tea intake in order to draw strong conclusions about green tea and breast cancer."

Why is the evidence that tea prevents cancer so strong in animals and test tubes, yet so weak in humans? "How much tea people consume versus how much is used in the animal experiments has always been a key issue," says Wu.

"The animals are typically fed very large amounts of tea, or what are thought to be tea's active ingredients," says Rutgers' Joshua Lambert. As a result, the concentration of those ingredients in the animals' tissues may be 10 times higher than in the tissues of people who drink tea.

"When you look at the animal studies that use levels of tea more comparable to the concentrations found in human tissues, you don't see an anticancer effect," says Nurulain Zaveri of SRI International, a nonprofit institute in Menlo Park, California, that conducts research for industry and the government.

"I think the value of the research we're doing will be in identifying how tea prevents cancer in animals and test tubes, and then developing drugs to do the same thing," she says.

Bottom line: Tea prevents cancer in animals, but in human studies, people who drink five or more cups a day have no lower risk. Few studies have tested tea extracts on cancer in people.

WEIGHT

A soft drink that helps you burn more calories? "For the first time you can actually 'drink negative,'" promise Coca-Cola and Nestle.

Last fall, the two companies began marketing a carbonated diet green tea drink called Enviga. Each 12-ounce can is fortified with 100 milligrams of caffeine and 90 milligrams of epigallocatechin gallate (EGCG), an antioxidant that occurs naturally in tea.

If you drink three cans of Enviga a day, you can burn an additional 60 to 100 calories every 24 hours, the companies claim. (Just expect to shell out about $4 a day, or $1,500 a year.)

Soft-drink manufacturers aren't the only ones putting EGCG in products designed to lure weight-conscious consumers. Bayer, for example, adds EGCG (32 mg) to One-A-Day WeightSmart multivitamins, "to supplement the effort you are making to better control your weight."

(In January, the U.S. Federal Trade Commission fined Bayer $3.2 million for making unsubstantiated claims that WeightSmart with EGCG helps trim pounds by boosting metabolism.)

Coke and Nestle deny that Enviga is intended to help people lose weight. Rather, it provides a "metabolic invigoration" to keep "those extra calories from building up." That kind of mushy "structure or function" claim requires no evidence.

Does tea--or the EGCG in tea--have any impact on weight? The evidence is pretty thin. In a handful of small studies that lasted only one to three days, people who took EGCG plus caffeine burned slightly more calories than those who were given a placebo:

* In two studies in 1999 and 2001, U.S. Department of Agriculture and Swiss researchers gave 22 healthy men oolong tea or a green tea extract over the course of one day. Both contained 244 mg to 270 mg of EGCG and 150 mg to 270 mg of caffeine. The men burned roughly 70 to 80 more calories than on the day they got a placebo. (9,10)

* Last November, in a study financed by Nestle, 31 young men and women consumed the equivalent of three 12-ounce cans of Enviga every day for three days. On the third day, they burned 60 to 100 more calories than on the third day they drank a placebo. (The study hasn't yet been published.)

But what happens after a few days? Do people eat more to compensate for the extra calories they're burning, or perhaps stop burning extra calories?

* When Dutch researchers added 596 mg of EGCG and 237 mg of caffeine to the diets of 23 overweight women who were trying to lose weight, the women burned no more calories after one month--and shed no more pounds over a 12-week period--than 23 similar women who were given a placebo. (11)

* When the same researchers added 270 mg of EGCG and 150 mg of caffeine to the diets of 38 men and women who had already lost weight, the dieters gained back as many pounds after 12 weeks as 38 similar people who were given a placebo. (12)

* In contrast, when Japanese researchers gave 136 mg of EGCG and 75 mg of caffeine to 17 dieters, the volunteers lost 2 1/2 more pounds after 12 weeks than 17 similar people who got a placebo. (13)

It's not clear why the volunteers--all overweight employees of a company that sells a green tea "suitable for people who are concerned about body fat"--would differ from the participants in other studies.

Bottom line: In a few very-short-term studies, people burned slightly more calories when given EGCG plus caffeine. But in longer-term studies, the combination had no consistent impact on weight.

(Note: The Center for Science in the Public Interest, Nutrition Action's publisher, has sued Coca-Cola and Nestle for implying in their ads that Enviga can help people shed pounds or keep from gaining weight.)

THE TEA BAG

Over the last 10 years, sales of ready-to-drink bottled teas like Arizona, Nestea, Snapple, Lipton, and Sobe have grown almost tenfold. While that's good news for the companies, it may not be so good for people who think they're getting real tea.

Oregon State University researchers have found that freshly brewed green or black teas contain 10 to 100 times more antioxidants than bottled teas.

The U.S. Department of Agriculture found much the same. According to its analyses, an 8-0z. cup of freshly brewed green tea contains 196 milligrams of the antioxidant EGCG, while a cup of bottled green tea contains just 9 mg.

And a cup of freshly brewed black tea contains 27 mg of EGCG, says the USDA, while a cup of bottled black tea has 1 mg--about the same as instant or diet teas. (Freshly brewed oolong tea contains 85 mg.)

"Many of the currently available cold bottled teas sold in the United States are more like diluted sugar water than something that may help protect your health," says Oregon State researcher Rod Dashwood.

(1) www.teausa.com/general/204g.cfm.

(2) Am. J. Epidemiology 154: 495, 2001.

(3) JAMA 296: 1255, 2006.

(4) Arch. Intern. Med. 163: 1448, 2003.

(5) Carcinogenesis 27: 1301, 2006.

(6) Br. J. Cancer 95: 371, 2006.

(7) Urol. Oncol. 23: 108, 2005.

(8) Carcinogenesis 27: 1310, 2006.

(9) Am. J. Clin. Nutr. 70: 1040, 1999.

(10) J. Nutr. 131: 2848, 2001.

(11) Br. J. Nutr. 94: 1026, 2005.

(12) Obes. Res. 13: 1195, 2005.

(13) Am. J. Clin. Nutr. 81: 122, 2005.