In Oslo, Norway, in 1934, an observant mother of two mentally retarded children noticed that their soiled diapers had an odd, musty odor. She mentioned this to Ivar Folling, a relative who was a physician and biochemist. Folling was intrigued. Analyzing the children's urine, he found large amounts of the amino acid phenylalanine, which is usually present only in trace amounts because normally an enzyme hastens a chemical reaction that breaks it down.

Because researchers knew that the mental retardation of PKU is caused by a buildup of phenylalanine, which is a normal component of protein, they wondered whether a diet very low in phenylalanine might prevent the mental retardation. The diet would include the other nineteen types of amino acids so that normal growth, which requires protein, could occur. The diet would theoretically alter the body's chemistry in a way that would counteract the over-abundance of phenylalanine caused by the two faulty genes.

In 1963, theory became reality when a dietary treatment for this otherwise devastating inherited illness was devised . The diet is very restrictive and difficult to follow, but it does prevent the otherwise inevitable mental retardation from developing. However, treated children may still have learning disabilities. We still do not know how long people with PKU should adhere to the diet, but it may be for their entire lives.

Copyright ©1998 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use and Privacy Policy.
McGraw-Hill Higher Education is one of the many fine businesses of The McGraw-Hill Companies.
For further information about this site contact mhhe_webmaster@mcgraw-hill.com.