Clinical staff at Children's try 'phe-free' diet

If you ask most kids what the essential food groups are, you're likely to get pretty standard answers: Pizza. Ice cream. Chicken nuggets. Grilled cheese.

But for children with a rare genetic disorder called phenylketonuria, or PKU, these foods can cause progressive mental retardation. High-protein foods, along with a host of others, contain an amino acid called phenylalanine. Most people need phenylalanine to stay healthy, and most people can break down the amount they take in. However, if someone has PKU he or she cannot break down phenylalanine, or "phe," and it will build to toxic levels.

"You'd be astonished at what contains phenylalanine," said Gail Brookshire, MS, C.G.C. a genetic counselor on staff at Children's. Milk, eggs, poultry, legumes and many products made from flour contain the amino acid. "Cilantro has it, even garlic. It's in things you wouldn't expect. There are not a whole lot of really satisfying foods children and adults with PKU can eat."

Brookshire is one of seven people in Genetics, Metabolism and Down Syndrome department at Children's who spent five days in November on the diet. The Metabolism outpatient service treats approximately 100 families who have one or more children with PKU.

"We know the diet is hard, but we wanted to know what it's like to live it," said Katie Green, MS, RD, LD, a dietician at Children's who works with the ambulatory services. Green prepared a modified version of the PKU diet for the team's experiment.

"We fully realize five days is nothing like the discipline it takes to be on this diet for your entire life," Brookshire said.

PKU diagnosis

Every state requires that all newborns be screened for PKU. If the child has PKU, the diet must begin right away to prevent mental retardation. Prior to the mid-1960s, when states began mandating PKU screening, many children diagnosed with the severe form of the disorder were destined to live in institutions.

The PKU diet is most crucial throughout infancy and early childhood as the brain is developing. Once a child reaches 5 to 7 years of age, straying from the diet just once or twice will not lead to serious problems; however, continued straying can lead to behavioral problems, low IQ and concentration problems.

"These kids can never just show up and eat what's being served at a party," Green said. "They can never walk past the kitchen and grab a banana if they're hungry."

Phe-free diet

Instead, they must eat meticulously measured portions of foods like spinach, grapes and other low-phe items. Breakfast might include 10 grapes and one-half cup of dry Honeycomb cereal. Lunch could be one-half cup of raw spinach, one-quarter cup of dried cranberries and one tablespoon of phe-free salad dressing, such as Kraft Honey Dijon. For dinner, the menu may include one cup of applesauce, 16 Ore-Ida Golden Crinkle french fires, one tablespoon of ketchup and a Hunts Lemon Snack Pack pudding. Brands are important because while one brand of honey Dijon salad dressing may be phe-free, another one may not.

Each child with PKU is prescribed a specific amount of formula, similar to a protein shake, which they must drink each day to make up for the nutrients they're not getting from typical protein sources. The formula is densely packed with all amino acids, minus phenylalanine.

Known as "PKU milk" among children with the disorder, the drink is nutritionally complete to make up for the nutrients these children don't get from food. It's filling, but some children don't care for the taste. Because it is all they have ever had, if the diet is maintained strictly, most children become used to it.

Rigid discipline

Besides gaining a better appreciation of the stringent diet, the Genetics and Metabolism team realized what a chore meal planning can be for families with children who have PKU. Everything a child with PKU eats must be precisely measured so that they do not go over the allotted number of phe exchanges.

"We're learning how very hard it is to count everything you put in your mouth and to write it down. You have to count everything," Brookshire said.

Keeping a log of everything they eat is important for PKU patients. If a child's phenylalanine levels are out of whack, his or her dietician can review the patient's food log and adjust the diet.

The payoff, though, is worth it. Those who stick to the diet for a lifetime live full, healthy lives.

Resources

Genetics
Metabolic disease

Tags: health