The Food and Drug Administration (FDA) has turned its eye to Cheerios' claim that the cereal is clinically proven to lower cholesterol.

The government agency told General Mills in a warning letter that if the cereal is being promoted for conditions that a drug could treat, it must be approved by the FDA as a drug.

The letter asserts that the cereal box was misbranded. Specifically under scrutiny is the packaging on the box and the brand's Internet advertising.