The synthesized chemical called ASPARTAME is the artificial sweetener that is used in many kinds of diet soda and other sweets. It has phenylalanine as an ingredient, but is itself a completely different chemical. Apartame can cause a wide range of side effects and is considered to be very unsafe by many people (including medical professionals). Some people complain that they get headaches, cramps, severe vomiting, seizures, etc... Indeed, when aspartame is heated it breaks down into a chemical that is comparable to wood alcohol (Don't ever drink a warm diet soda or consume any warm food that has aspartame in it!).