This is a sweetener used in a lot of sugar-free foods, especially chewing gum. There are no records of cats becoming ill from this product, but in dogs it can cause a severe drop in blood sugar — which can cause seizures and convulsions or even death — followed by liver failure.
However, as this sweetener is used in more products that cats might be attracted to such as peanut butter, it’s better to be safe and not let your cat eat foods that contain this ingredient.