When protein is digested in your body, it is broken down into smaller units called amino acids, the building blocks of proteins. There are 20 amino acids and 10 are essential in the human body. These amino acids are absorbed into the digestive tract and build proteins, help make other molecules or are broken down into the urine. Phenylalanine is one essential amino acid. Essential amino acids such as phenylalanine cannot be made within the body, and must be received in your diet.
People with phenylketonuria, or PKU, are deficient in the enzyme phenylalanine hydroxylase, PAH. Without this enzyme, they cannot turn the phenylalanine into tyrosine and it builds up in the blood and the urine. When phenylalanine builds up, it is very dangerous.
Diagnosis of PKU
A diagnosis of PKU is made when the blood level of phenylalanine is greater than 20mg/dl. The tyrosine levels can also be looked at. In combination with high phenylalanine levels, if the tyrosine levels are low, this can assist in making the PKU diagnosis.
Dietary Restrictions for Those With PKU
The therapy for PKU is the dietary restriction of phenylalanine as soon as possible. To keep phenylalanine levels low, the parent and the patient must work with a dietitian and a physician on which foods to avoid. Foods such as dairy, eggs, soy, beef, poultry, fish, nuts, seeds and artificial sweetener with aspartame. Special medical foods, such as Lofenalac, which is a phenylalanine-free protein substitute, are good alternatives for both infants and adults. Certain fruits, vegetables, low protein breads and pastas can be eaten on a low phenylalanine diet.
Low Long Chain Fatty Acids with Phenylketonuria Dietary Restrictions
Some long chain fatty acids are missing from the diets of those with PKU. Supplementation to replace these long chain fatty acids can assist and improve motor coordination.
The Ketogenic Diet
The ketogenic diet uses high fat, or long chain fatty acids, low carbohydrate and normal protein intake to put the body into starvation state. The diet is usually started with a fast, which changes levels of insulin, glucagon, plasma ketones, glucose and free fatty acids to control seizures in those with epilepsy. The diet should always be initiated by a registered dietitian.
Some people with PKU experience seizures and also have low levels of long chain fatty acids. The ketogenic diet, in combination with low levels of phenylalanine, might control seizures, and the long chain fatty acids might help to improve motor function.
There is little to no research supporting the idea that the ketogenic diet can improve symptoms of PKU. If the ketogentic diet is given to an individual with PKU without the restriction of phenylalanine, he will be at risk for brain damage. Those with PKU must have a lifelong commitment to the restriction of phenylalanine in their diet. Talk with your dietitian and physician before starting any new type of restriction diet.
References
- "Molecular Genetic Metabolism"; Structure Basis of Phenylketonuria; Erlandsen, et al.; October 1999
- "Pediatrics"; National Institutes of Health Consensus Development Conference Statement: Phenylketonuria: Screening and Management October 16-18 2000; October 2001
- "European Journal of Pediatrics"; Diet and Compliance in Phenylketonuria; Macdonald; October 2000
- "Journal of Inherit Metabolic Disorders"; Lipid Status and Fatty Acid Metabolism in Phenylketonuria; Giovannini; 1995
- "Epilepsia"; Anticonvulsant Mechanisms of the Ketogenic Diet; Bough KJ, et al.; January 2007
Member Comments