Dangers of Phenylalanine
What If I Have Undiagnosed PKU?Some people may be concerned that they have PKU and not know it. In fact, some anti-aspartame Web sites go as far as to recommend PKU testing for adults. However, PKU is almost always diagnosed in early infancy, due to required infant screenings done shortly after birth, and people with undiagnosed (and, therefore, untreated) PKU do not reach adulthood without significant problems, such as severe mental retardation. Rest assured that if you have PKU, you will definitely know it.
Final ThoughtsUnless you have PKU, phenylalanine is just a necessary amino acid that should not cause any worry or fear. The presence of phenylalanine in aspartame should not be reason enough to avoid aspartame (after all, if you want to avoid phenylalanine, you will need to cut out a wide range of natural foods as well). Remember that just because phenylalanine can be dangerous if it builds up to extremely high levels in the body, this does not mean that normal intakes are also dangerous. Many necessary and beneficial chemicals or substances in the body are toxic at very high levels.