Over the years, people have reported to FDA adverse reactions to certain food additives, including aspartame (a sweetener), monosodium glutamate (a flavor enhancer), sulfur-based preservatives, and tartrazine, also known as FD&C Yellow No. 5 (a food color). The federal Food, Drug, and Cosmetic Act requires that FDA ensure the safety of all substances added to foods, but individual health conditions sometimes cause problems with certain additives.