PKU Diet Therapy?
Dietary therapy is a lifelong treatment to keep PKU disease under control. Due to an innate genetic damage, enzymes are not secreted from the liver. The amino acid "phenylalanine" taken into the body with foods needs to be converted to the "tyrosine" amino acid. But it cannot transform. The blood rich in phenylalanine is transported to the brain and begins to harm the brain. And of course to other organs, as well… Phenylalanine is an essential amino acid which means amino acids taken from the food that the body cannot produce by itself. There are 20 types of amino acids that make up the structure of proteins. 8 of these are essentials. In other words, amino acids that must be taken with foods and phenylalanine is one of them.
When phenylalanine is taken into the body through foods, approximately 50% of the enzyme “FAH” in the liver is converted into another amino acid called tyrosine. In the other 50%, it is used in the synthesis of the necessary proteins for the body. This 50 %, which cannot be converted, begins to accumulate in the blood. If the phenylalanine taken cannot be converted and accumulates, it is necessary to stop or limit the intake of phenylalanine. Dietary therapy is also based on this: to limit the amount of phenylalanine taken with foods or to ensure its controlled intake. Thus, the level of phenylalanine in the blood is taken under control.
How Is the Diet Carried Out? 
Phenylalanine is the building block of many proteins. It is not possible to extract only this amino acid from foods containing protein. Therefore, diet restricted from phenylalanine means restricted diet from protein. That is, if the amount of protein is low, the amount of phenylalanine will be low, too. That's why diet therapy is based on low protein intake. Restricted or forbidden diet from protein foods means not being able to eat 80 % of normal foods. It means that high-protein foods such as red meat, fish chicken, eggs, milk, cheese are completely prohibited. It means that vegetables and fruits and cereals (pasta, rice, bread, bakery products etc.) and chocolate and chocolate products can be consumed in certain amounts. Almost all of the foods we consume daily are restricted or prohibited, making it compulsory to develop alternative foods. For this, there are “special nutritional products” sold commercially by various companies. These products are substitutes for reality. High protein products are used as imitation as taste and flavor by using low protein ingredients: Low protein flour mixtures, milk, pastas, chocolates, egg substitutes, meat substitutes ... both create variety in diet and relax the patient psychologically and makes the diet easier to manage. Apart from these, there are foods that are free to consume, such as juices, tea, tea sugar, rock candy, corn starch. These foods do not contain phenylalanine. Therefore, it can be consumed without limitation.
How Will the Body's Protein Needs Be Met?
Another issue is how to live life by avoiding protein ... Protein is one of the main components of life. It is necessary for many basic functions such as growth, development and mental functioning. How will a healthy life be possible without protein? For this, there are formula foods. The patient should use these foods for a lifetime. These foods, which are restricted from phenylalanine and combined with other amino acids, provide the body with the necessary amino acids. In addition, it is enriched with vitamin and mineral supplements and other components needed by the body are reinforced. Research shows that despite adequate iron intake, iron deficiency occurs in PKU patients. The PKU diet especially reduces the absorption and use of B6 and B12 with calcium, phosphorus and vitamin D. Therefore, these components must be added to the diet.
Dietary Compliance 
The goal in the PKU diet is to adhere to the low-protein diet continuously and without interruption. It is very difficult to return to the diet after the PKU diet is stopped. The most important reason for this is recorded as decreased motivation. Decreased dietary motivation is associated with the immediate consequences of incompatibility. In other words, if the PKU diet is not followed, its effect is not seen immediately like diabetes disease. However, findings such as increased irritability, difficulty concentrating and headache in individuals who do not follow the diet are noticed by family members. The PKU diet is easily followed in early childhood and before starting school. In adolescence, compliance with diet becomes an important problem. With the onset of children's own food choices at school, problems with diet compliance also increase. The biggest problem in diet compliance is with the consumption of amino acid-based foods. These foods make the consumption of obvious bad taste and odor difficult. Most children refuse to drink this formula at school. Deprivation of the protein source during the 8-hour school period causes the destruction of the existing proteins in the body. It is more important to use formula foods during the growing period. Formula foods are necessary for promoting growth, especially in adolescence; it also helps increase the tolerance of phenylalanine. Because the amino acids in formula promote protein synthesis in the body. Meanwhile, phenylalanine is involved in protein synthesis. Thus, the level of phenylalanine in the blood decreases. Since PKU requires life-long dietary treatment, it is very important for children and adolescents to learn the importance of diet. It is necessary to gradually take responsibility from early ages in order to create healthy habits for children and prevent leaks in the diet. Thus, the practices learned in childhood continue in adulthood and the patient is adhered to the diet throughout his life.
Gülşah Kurtoğlu
Food Engineer