The claims seemed amazing: Amon Orchards of Acme, Mich., said on its Web site that "cherries prevent cancer." Brownwood Acres Foods Inc. of Eastport, Mich., said cherries "knock out gout," a painful joint disease. And according to Cherry Lands Best of Appleton, Wis., the tiny red fruit can "fight heart disease."

Amazing -- and unproven. Now the government is telling these and other companies to stop making such claims.

The Food and Drug Administration sent letters last week to 29 fruit growers and packagers warning them that such declarations are "serious violations" of federal food labeling laws. It is the first time the agency has acted uniformly against a food group. To place health claims on labels, companies must file a petition with the FDA providing scientific evidence and get approval from regulators.

"There have been some in the past where it's been for one particular food product, or one particular company," said Kimberly Rawlings, a spokeswoman for the FDA. "This is the first major type of conventional food that has received warning letters."

The agency took enforcement action after being alerted to numerous tart cherry producers making health claims that would be legal on only tested, approved pharmaceuticals, Rawlings said. The letters were sent Oct. 17, and the companies have 15 business days to respond. Some have already made revisions to their Web sites, while others have not.

"There's a lot of exuberance about cherries. Maybe that exuberance spread into statements that should not have been made," said Jane DePriest, marketing director for the Cherry Marketing Institute, a trade group that represents cherry farmers and marketers. "But no one, including the Cherry Marketing Institute and the companies involved, intended to mislead people."

DePriest said the institute is familiar with the strict and bureaucratic process companies must go through to get permission from the FDA to make any kind of health claims on food packages, but she said the companies are "responsible for knowing the law."

No one in the cherry industry has filed a petition to make health claims, nor does anyone have plans to do so at this point, DePriest said. The industry's claims stem from a growing body of research pointing to the positive health effects of antioxidants in various fruits, including the strong dose found in sour cherries. In the vitamin and supplement industry, some companies already have permission from the FDA to make "function" claims about cherry juice extract.

Enzymatic Therapy Inc. of Green Bay, Wis., for example, has permission to say its cherry fruit extract supplements "supports the integrity or health of capillaries, collagen structure, eyes, joints and arteries," said Robert Doster, the company's senior vice president of scientific affairs. "We're deriving our claims on the basis of a very large body of research that's already been done on cherry fruit."

Labeling experts say small food companies typically are not targeted by the FDA because the agency has few resources to target the many tiny firms marketing to consumers. But this action sends a message.

"I think maybe this will put a stop to this feeling that smaller outfits can get away with anything, and that's good," said Fergus M. Clydesdale, head of the Department of Food Science at the University of Massachusetts at Amherst.

Clydesdale and others support the idea of health claims on food packages if the underlying science meets a high enough level of proof. But the FDA has been trying to develop a system that would allow manufacturers to make health claims even when the evidence is still developing, and that has proved confusing to consumers, said David B. Schmidt, incoming president of the International Food Information Council, a District-based nonprofit group.

What there is no confusion about, he said, is the problem of companies making health claims that have not been vetted or approved by regulators at all.

"If you make it sound like a drug claim, you really are overpromising to consumers and damaging consumer confidence," he said.

The FDA issued a

warning to 29 fruit growers and packagers on cherry-related claims.