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Newborn blood tests and diet soda - what's the link?

by Dr. SeANNE Safaii-FabianoLD University of Idaho
| March 16, 2010 9:00 PM

The words "phenylketonurics: contains phenylalanine" is on every food product containing aspartame as a sweetener. But have you ever stopped to wonder what it means and why it is included on the label?

Most states (including Idaho) require a simple blood test after a baby is born to determine whether they have certain conditions that could eventually cause problems. Even though these conditions are rare, an early diagnosis and proper treatment can make the difference between healthy development, lifelong impairment and in some cases death.

Many of these conditions are metabolic disorders (often called "inborn errors of metabolism") that interfere with the body's use of nutrients to maintain healthy tissues and produce energy. Other disorders that screening can detect include problems with hormones or the blood. Parents can pass along the gene for certain of these conditions without even knowing that they're carriers.

One of these metabolic disorders is Phynelketonuria (PKU). People with PKU lack an enzyme needed to process the amino acid phenylalanine, which is an essential amino acid needed for growth and development in children and adults. If too much phenylalanine builds up in these children, brain damage and substantial developmental delays can result.

In fact prior to 1960, when newborn screening didn't exist, many of these children wound up in state hospitals for the developmentally delayed with irreversible damage.

The good news, is that PKU occurs in only about one in 15,000 births. Babies identified with PKU are immediately placed on a special diet with minimum amounts of phenylalanine -each child has different tolerance levels. It is recommended that they stay on this low-phe diet for life.

That's why any foods using aspartame as a non-nutritive sweetener must identify this on their label. There are some new drugs on the horizon that will help boost the ability of a person with PKU to break down phenylalanine, but the current standard of treatment is dietary intervention.

One of the most rewarding aspects of my career as a dietitian has been working with families affected by PKU. Through early identification, dietary intervention and continuous monitoring of blood phenylalanine levels, children with PKU live happy, healthy and productive lives. What a contrast to sit in a clinic next to someone born in the 1950s with PKU who has no language skills and on my other side is someone who was diagnosed in the 1980s and is a pre-med student. How far we have come!