The FDA has given a thumbs-down on a bid to label green tea as a cancer fighter.

Current scientific evidence from human studies doesn’t support the claim, says the FDA’s Michael Landa.

Landa is the deputy director for regulations at the Center for Food Safety and Applied Nutrition. He wrote the FDA’s response to a green tea company’s proposed cancer-prevention claim.

FDA’s Verdict

Landa doesn’t totally dismiss green tea. Future research will be considered, he says.

For now, he says it is “highly unlikely” that green tea cuts breast cancer or prostate cancer risk.

Landa also says there is “no credible evidence” supporting green tea as a fighter of other cancers, including lung, gastric, colon, rectal, pancreatic, esophageal, skin, ovarian, or liver cancers.

Read WebMD's "Green Tea's Record Against Cancer Grows"

Reading the Tea Leaves

All tea comes from the same leaves, but processing methods produce different types of tea. White tea is the least processed tea type; it’s made from buds and young leaves. Next is green tea -- which is made from more mature leaves -- and black tea.

Tea is packed with antioxidants, which have been studied for their potential against cancer and heart disease. The type of tea determines the amount and types of antioxidants.

The FDA’s review only addressed cancer.

Green tea has been found to have cancer prevention activity in animal studies. The flavonoids found in tea are known for their ability to alter cell pathways that may lead to cancer.

Read WebMD's "Green Tea: The Next Performance Enhancer?"

Studies of Green Tea

Many green tea studies have been done on animals, or on cells in lab tests. Some have also tracked health among large groups of people who drink a lot of tea.

For instance, researchers unleashed antioxidants called phenols from tea on human breast cancer cells in a lab experiment. The tea phenols had a sizeable impact on breast cancer cell growth, the researchers said in April 2004.

Other experiments have targeted human prostate and bladder cancer cells. Those cells were placed in mice, where they were treated with a green tea extract.

The FDA’s Review

The data on green tea reviewed by the FDA included only human studies.

Studies done on humans have inconsistent evidence. Some of those studies showed decreased cancer risk for breast and prostate cancers, but others didn’t. A lot of the data were “weak and limited,” says Landa.

Some research on stomach cancer -- done in Japan -- got benched because the disease and salt intake differs in Japan and the U.S., says Landa.

Read WebMD's "Green Tea Fights Fat"

Nuts, Oats Ahead of the Pack

Some other foods bear FDA-approved health claims.

Packages of nuts and whole-oat foods can carry labels touting possible heart benefits.

Nuts got the nod from the FDA nearly two years ago. Oats were OK’d for the labeling back in 1997.

The FDA’s standards for food claims aren’t as strict as its approval process for new drugs.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: News release, FDA. FDA, “Letter Responding to Health Claim Petition dated Jan. 27, 2004: Green Tea and Reduced Risk of Cancer Health Claim.” WebMD Medical News: “Wine, Beer, Tea May Slow Breast Cancer.” WebMD Medical News: “Green Tea’s Record Against Cancer Grows.” WebMD Medical News: “FDA OKs Nutty Heart Health Claim.” Talk paper, FDA. The Linus Pauling Institute.