Phenylketonuria – Medical Treatment, Diet, and Nutritional Guidelines

Phenylketonuria is a congenital metabolic disorder affecting approximately 1 in 7000–8000 newborns in Poland. The condition arises from a deficiency or reduced activity of the enzyme phenylalanine hydroxylase, which is responsible for converting phenylalanine into tyrosine. As a result, phenylalanine accumulates in the body, potentially leading to irreversible damage to the nervous system. Symptoms of elevated phenylalanine levels include concentration difficulties, learning challenges, and excessive physical activity. Without treatment, the disorder can result in severe consequences, particularly irreversible damage to the central nervous system. Early implementation of a phenylalanine-restricted diet is crucial, especially in infants. Diagnosis is made through screening tests, with levels above 10 mg/dl necessitating strict adherence to the diet (D. Włodarek et al. 2015).

The cornerstone of phenylketonuria treatment is a diet that restricts phenylalanine intake. This is the only proven method of managing the condition. A low-phenylalanine diet must be maintained throughout life, with particular emphasis on adherence during infancy. In cases of phenylketonuria, an infant's diet differs from that of a healthy newborn. There are two primary approaches: a phenylalanine-free diet or specially prepared breast milk. Numerous phenylalanine-free infant products are available, marked with the abbreviation PKU. When breastfeeding, the milk must be expressed and measured appropriately, taking into account phenylalanine levels. Newborns tolerate higher amounts of this amino acid than adults, but the daily dose should not exceed 30–50 mg/kg of body weight. In older children, tolerance ranges from 10–20 mg/kg, while adults should not exceed 5–10 mg/kg (D. Włodarek et al. 2015). Early dietary intervention prevents learning difficulties and enhances concentration and intelligence. In atypical forms of phenylketonuria, pharmaceutical preparations such as tetrahydrobiopterin are also used (E. Jameson, T. Remmington 2020). Foods high in phenylalanine, including meat, eggs, and milk, should be avoided. To prevent protein deficiency, substitute preparations are used, which should cover 80% of daily protein requirements. The remaining needs are met through low-phenylalanine foods (N. Al Hafid, J. Christodoulou 2015). Fat and carbohydrate intake should align with recommendations for healthy individuals.

Permitted products include those that do not naturally contain phenylalanine. While there are relatively few such items, they can be consumed without restrictions, provided one exercises common sense (D. Włodarek et al., 2015). Examples include: - honey, - mineral water, - vegetable oils, - sugar, - tea, - fruit candies.

Due to their phenylalanine content, the intake of these products should be carefully monitored. Excessive consumption may result in elevated amino acid levels in the blood (J. C. Rocha, A. MacDonald 2016).

The catalog of restricted items in a low-phenylalanine diet is considerably more extensive than the list of permitted foods. Excluding the following products may substantially lower phenylalanine levels in the patient's bloodstream (D. Włodarek et al., 2015). Prohibited categories include: – meat and meat products, – fish, – eggs, – dairy and milk derivatives, – legumes, – grains (excluding previously mentioned), – nuts, – seeds and kernels.

Currently, there are numerous products available for individuals with phenylketonuria. Due to increasing interest in this condition, food alternatives with lower phenylalanine content are being produced. In stores, one can find bread, flour, pasta, rice, puddings, and cakes. This type of food is labeled as PKU and is typically found in the health food section. Additionally, there are specialized PKU stores and websites offering such products. These items diversify the diet of affected individuals and significantly facilitate adherence to strict dietary guidelines. Over time, following such a diet becomes easier, and meal planning becomes more efficient. Phenylalanine tolerance is individual and requires dose adjustment, which is possible through consultations with doctors and dietitians. Both insufficient and excessive phenylalanine intake can be harmful to health. In addition to previously mentioned symptoms of excess, fatigue, anemia, and appetite disturbances may occur, which result from too low an amino acid level in the blood. To better control phenylalanine intake, specialized tables can be used, which doctors and dietitians often provide to their patients. Additionally, the internet contains information about the amino acid content in various food products. To monitor phenylalanine levels in the blood, regular laboratory tests are necessary. In the first year of a child's life, these should be conducted weekly, children up to 12 years old should have them every two weeks, and older children and adults should have them monthly. This allows for the assessment of amino acid levels and the impact of diet on this parameter. If medically necessary, a doctor may order more frequent blood tests.

Phenylalanine per serving: 79.5 mg Ingredients (per serving): – pumpkin – 1 glass, – carrot – 1 piece, – parsley – ½ piece, – water – ¾ glass, – olive oil – 1 teaspoon. Preparation method: 1. Peel the pumpkin, remove seeds, and cut into cubes. 2. Wash the carrot and parsley thoroughly, peel, and slice thinly. 3. Place vegetables in a pot, cover with water, and simmer until tender (approx. 20 minutes). 4. Remove from heat and blend the contents into a smooth consistency. 5. Pour the soup onto a plate and garnish with olive oil.

This dish contains 93.3 milligrams of phenylalanine. Ingredients per serving include: PKU pasta (quantity: one glass), olive oil (quantity: one teaspoon), onion (quantity: one piece), spinach leaves (quantity: two handfuls), and cherry tomatoes (quantity: one handful). Preparation: 1. Cook the pasta in salted water. 2. Heat the olive oil in a pan and sauté the diced onion. 3. Add the spinach and simmer on low heat with a lid for approximately 10 minutes. 4. Then, add the cooked pasta and mix thoroughly. 5. Transfer to a plate and top with sliced cherry tomatoes.

Phenylalanine content: 69.5 mg. Ingredients (per serving): celery stalk – one stalk, avocado – half a fruit, apple – one fruit, water – one glass, olive oil – one tablespoon. Preparation method: 1. Thoroughly wash, peel, and chop the fruits into smaller pieces. 2. Combine all ingredients in a blender and blend until smooth.