Lack of Appetite & PKU

Phenylketonuria, or PKU, is the result of the mutation of a single gene. The genetic mutation causes children born with PKU to be unable to convert the amino acid phenylalanine into tyrosine. Excess phenylalanine then accumulates and causes serious damage to the nervous system, potentially even brain damage and mental retardation.

Diagnosis

Infants must be tested for PKU within days of their birth to prevent the irreversible damage that phenylalanine accumulation causes. A simple blood test measures the level of the enzyme needed to metabolize phenylalanine. If the enzyme is missing, the infant has PKU. The test is performed at least twice -- once at 12 to 28 hours after birth and again when the infant is about 1 week old.

Low Appetite

One of the symptoms of PKU is poor appetite. Children who have phenylketonuria tend to develop more slowly than other children because their reduced appetites lead them to eat less than they need to realize their full growth potential. To counteract the negative effects of poor appetite, the PKU diet should be as palatable as possible and offered in an enjoyable, low-stress environment.

PKU Infant Diet

Infants can drink breast milk -- which is naturally lower in phenylalanine than are commercial formulas -- as long as the serum level of phenylalanine stays between 130 to 360 umol per liter. A medical professional will calculate the amount of phenylalanine in breast milk and compare it to the amount needed to maintain the appropriate serum level. Once the serum needs have been met, you will give any additional feedings using a phenylalanine-free formula. If you prefer not to breastfeed, you'll use a formula with a carefully calculated amount of phenylalanine.

PKU Diet

The PKU diet consists primarily of low-protein foods like fruit, vegetables and low-protein breads. To maintain the necessary intake of protein, including phenylalanine, most people with PKU supplement their diet with a special protein beverage. Because it is often easier for people with poor appetites to drink a nutritive beverage than to eat a meal, the formula has the added benefit of working around any appetite problems. By drinking the prescribed amount of formula every day as well as eating a variety of low-protein foods that you find appealing, you can maintain a normal lifestyle and normal health.

Aspartame

Aspartame, which is also sold as NutraSweet, contains phenylalanine. Mothers who are pregnant or nursing should avoid foods and beverages containing aspartame because of the risk posed to the infant by the high levels of phenylalanine. Likewise, people who have PKU must avoid eating or drinking anything that contains aspartame.