The U.S. Food and Drug Administration warned General Mills Inc. (GIS) that labeling for its popular Cheerios-brand cereal contains "serious violations" of federal law relating to claims about the product's ability to lower cholesterol.

In a May 5 warning letter sent to the company and posted on the FDA's Web site Tuesday, the agency said statements that the product is "clinically proven to help lower cholesterol actually cause the product to be a drug under federal law.

The FDA said cholesterol-lowering claims can only be made if the product were to be approved as a drug. The product label says Cheerios can lower cholesterol by 4% and cited a clinical study involving the product as part of a diet low in saturated fat and cholesterol. The FDA said Cheerios "can't be legally" marketed with claims it lowers cholesterol by a certain percentage without an approved new drug application.

"We try to make a bright line here between what can be said about a drug and what can be said about a food," said Stephen Sundlof, the director of FDA's Center for Food Safety and Applied Nutrition. He explained that certain claims for a possible reduction in heart-disease risk from eating whole grain foods is allowed as long as specific language is used.

While Sundlof said "there's no specific campaign" to go after food manufacturers, he said the agency is noticing a "tendency" of more food companies crossing the line into the drug arena by adding additional health claims on product packaging which could spark more warning letters.

The FDA also took issue with a company-sponsored Web site mentioned on the Cheerios box. The Web site discusses the benefits of eating whole grains, but the FDA said some of the health claims about reducing cancer and heart-disease risk don't comply with agency rules regarding health claims for whole grains.

In a statement, General Mills spokesman Tom Forsythe said, the message saying "lower your cholesterol 4% in 6 weeks" has been featured on the box for more than two years and claims about heart health have been FDA-approved for 12 years.

"The scientific body of evidence supporting the heart health claim was the basis for FDA's approval of the heart health claim, and the clinical study supporting Cheerios' cholesterol-lowering benefit is very strong," he said. Forsythe said the company, however, would work with the FDA to reach a solution on product labeling.

The FDA said General Mills must "promptly" correct the violations outlined in the letter or the agency could take enforcement action, such as seizing products.

Sundlof said the FDA's review of Cheerios was prompted by a September 2008 letter from the National Consumers League that asked the FDA to look into its concerns about the Cheerios labeling on cholesterol.

Last month the Federal Trade Commission settled a complaint with Kellogg's involving claims that its Frosted Mini-Wheats cereal was clinically shown to improve children's attentiveness by nearly 20%. FTC Chairman Jon Leibowitz said the commission would start paying more attention to national advertisers.

-By Jennifer Corbett Dooren, Dow Jones Newswires; 202-862-9294; jennifer.corbett@dowjones.com