The makers of Cheerios made inappropriate health claims about the cereal's ability to lower cholesterol, the U.S. Food and Drug Administration said in a letter released Tuesday.

Packaging and internet ads for Cheerios Toasted Whole Grain Oat Cereal suggest the cereal is intended to lower cholesterol and to treat, mitigate and prevent coronary heart disease — claims that can only be legally made by FDA-approved drugs, the regulator said.

Labels also state: "You can lower your cholesterol four per cent in six weeks," but companies "cannot state a degree of risk reduction for coronary heart disease," according to the FDA letter, which is dated May 5.

The message has been on boxes of the O-shaped cereal for more than two years, and the science behind the claims "is not in question," General Mills spokesman Tom Forsythe said in a statement.

The FDA's complaints deal with how language appears on the box, the cereal maker said.

In its letter, the FDA questioned the health claim on the front label, saying it is separate from a cholesterol claim that mentions a clinical study found on the back of the Cheerios box.

The FDA said a General Mills website promoting whole grain products also made unauthorized claims about Cheerios and a reduction of heart disease and cancer. The claims left out required references to fruits, vegetables and fibre content.

General Mills has 15 days to say how it would correct the violations, the FDA said in its warning letter.

The regulator sends dozens of such warning letters each year. Most are resolved without further action, but product seizures and penalties can occur.

Health Canada allows products to claim a relationship between "a healthy diet low in saturated and trans fat and reduced risk of heart disease."

With files from The Associated Press