Why do rolled oats smell rancid?

Rolled oats can smell rancid due to the oxidation of fats present in the oats. When oats are exposed to air, light, or heat, the natural oils can break down, leading to off odors. This rancidity can be exacerbated if the oats are stored improperly or for extended periods. To prevent this, it's best to store rolled oats in a cool, dark place in an airtight container.