Hey, General Mills: If you want to say Cheerios is “clinically proven to lower cholesterol,” you better get your whole-grain Os approved as a new drug by the FDA.

That’s what the FDA told the company in this letter, which says the labeling on Cheerios boxes is in “serious violation” of federal rules. The letter continues:

Based on claims made on your product’s label, we have determined that your Cheerios® Toasted Whole Grain Oat Cereal is promoted for conditions that cause it to be a drug because the product is intended for use in the prevention, mitigation, and treatment of disease.

What’s more, the letter says, Cheerios “may not be legally marketed with the above claims in the United States without an approved new drug application.” (WSJ).