Principles of phenylalanine-restricted diet
Phenylalanine, an essential nutrient, is not only required for protein synthesis but also serves as a precursor for tyrosine and its derivatives. In the absence of phenylalanine hydroxylase, tyrosine becomes an essential amino acid.
Therefore, the technical challenge of the dietary treatment is to devise a phenylalanine-controlled diet that allows the reduction of systemic phenylalanine concentration, satisfactory tyrosine provision, and optimal growth and development.
Natural foods provide a measured amount of the offending phenylalanine in a quantity sufficient to meet the normal metabolic requirement but not so great that toxic levels accumulate in the blood. This amount of phenylalanine intake, usually called tolerance, is individually determined and varies from 1 patient to another depending on PAH residual activity, anabolism, and rate of growth.
Reducing the phenylalanine solely by restricting dietary protein from natural food would cause protein malnutrition and nutrient deficiency. Thus, such diets necessitate the use of phenylalanine-free amino acid formula containing adequate amounts of nitrogen, vitamins, minerals, and micronutrients. These dietary products have progressively been refined but remain unpalatable and are a frequent source of difficulty with the diet.
At the start of treatment in infants, a period of phenylalanine-free milk brings blood levels down. As levels approach the therapeutic range, phenylalanine is added using measured amounts of normal milk and then adjusted until serial blood controls have stabilized. This period of treatment is quite easy to manage but is the most important time for parents' education.
Once the addition of solids begins, the diet is progressively adapted with the following main principles explained to the parents and later to the patients: High-protein foods (meat, fish, eggs, dairy, and wheat products) are excluded. Foods with low-protein content (milk, vegetables, and fruits) are used to meet the required amount of phenylalanine. To allow calculation and diversification of the diet, serving lists were established in which 1 weighed portion is equivalent to a previously determined amount of phenylalanine (usually 15–20 mg). Low-phenylalanine foods either natural (fat and carbohydrates) or manufactured (special bread, biscuits, pasta, and flour) are free and useful in meeting the energy requirement and to satisfy the appetite of these growing children.
Principles of phenylalanine-restricted diet
Phenylalanine, an essential nutrient, is not only required for protein synthesis but also serves as a precursor for tyrosine and its derivatives. In the absence of phenylalanine hydroxylase, tyrosine becomes an essential amino acid.
Therefore, the technical challenge of the dietary treatment is to devise a phenylalanine-controlled diet that allows the reduction of systemic phenylalanine concentration, satisfactory tyrosine provision, and optimal growth and development.
Natural foods provide a measured amount of the offending phenylalanine in a quantity sufficient to meet the normal metabolic requirement but not so great that toxic levels accumulate in the blood. This amount of phenylalanine intake, usually called tolerance, is individually determined and varies from 1 patient to another depending on PAH residual activity, anabolism, and rate of growth.
Reducing the phenylalanine solely by restricting dietary protein from natural food would cause protein malnutrition and nutrient deficiency. Thus, such diets necessitate the use of phenylalanine-free amino acid formula containing adequate amounts of nitrogen, vitamins, minerals, and micronutrients. These dietary products have progressively been refined but remain unpalatable and are a frequent source of difficulty with the diet.
At the start of treatment in infants, a period of phenylalanine-free milk brings blood levels down. As levels approach the therapeutic range, phenylalanine is added using measured amounts of normal milk and then adjusted until serial blood controls have stabilized. This period of treatment is quite easy to manage but is the most important time for parents' education.
Once the addition of solids begins, the diet is progressively adapted with the following main principles explained to the parents and later to the patients: High-protein foods (meat, fish, eggs, dairy, and wheat products) are excluded. Foods with low-protein content (milk, vegetables, and fruits) are used to meet the required amount of phenylalanine. To allow calculation and diversification of the diet, serving lists were established in which 1 weighed portion is equivalent to a previously determined amount of phenylalanine (usually 15–20 mg). Low-phenylalanine foods either natural (fat and carbohydrates) or manufactured (special bread, biscuits, pasta, and flour) are free and useful in meeting the energy requirement and to satisfy the appetite of these growing children.
การแปล กรุณารอสักครู่..