Dietary Therapies for Medical Disorders: Finding a Way to Make Them Work. (Diet & Nutrition)(Cover Story)
Dietary Treatment for medical disorders has been prescribed for various ailments since the early 1960's. It is well established that dietary therapy for metabolic disorders and early stage renal disease can eliminate or delay the disease's sequelae.
Increasingly, researchers identify dietary treatments and restrictions for many more disorders, such as celiac sprue, autism, Parkinson's and others. For well-established dietary therapies, such as the low-protein metabolic diets, the efficacy is tremendous--yet maintaining the diet regimen is extremely difficult.
Foods that are low in protein, typically, do not taste good. Individuals with Phenylketonuria (PKU), Maple Syrup Urine Disease (MSUD), Tyrosinemia, Urea Cycle Disorders and Homocystinuria, which all require low-protein diets, are aware of this, and have been forced to endure medicinal tasting meals. However, a number of companies are now finding alternatives.
PKU is a rare inherited metabolic disease that can lead to mental retardation and other disabilities if it is not treated. For those with PKU, the body is unable to produce an enzyme in the liver needed to convert the amino acid, phenylalanine into another essential amino acid, tyrosine. As a result, excess amounts of phenalalanine accumulates in the body, which is toxic to the central nervous system and can cause brain damage. PKU can be diagnosed through routine newborn screening.
Treatment includes a diet that is extremely low in phenylalanine. Strict compliance to the diet is necessary in preventing or minimizing mental retardation. This requires close supervision by a registered dietitian or physician. Phenylalanine occurs in dairy, eggs, meat, fish, legumes and products made with commercial flours such as bread, cookies, cakes, snacks, etc. Recommended foods include fruits and vegetables in restricted amounts and special low protein foods. Treatment also includes an essential special formula made for people with PKU. It can be used throughout life as a protein source that is extremely low in phenylalanine and balanced for the remaining essential amino acids.
MSUD is an inheritable metabolic disease of amino acid metabolism characterized by acidosis, central nervous system symptoms, and urine that may smell sweet like maple syrup.
It is caused by the inability to metabolize the amino acids leucine, isoleucine and valine. In the most severe form, MSUD causes severe acidosis during the first week of life. This is characterized by progressively poorer feeding, vomiting, seizures, lethargy and coma.
Untreated infants may die in the first few weeks of life in severe forms of the disease. MSUD also occurs in an intermittent form and a mild form. Even in the mildest form, MSUD can result in mental retardation and bouts of acidosis precipitated by stresses such as ordinary infections.
Treatment requires dietary restriction of branched-chain amino acids, a special medical formula and intensive dietary monitoring.
Tyrosinemia is a genetic inborn error of metabolism, involving the amino acid tyrosine and is associated with a lack of the enzyme Fumarylacetoacetate Hydrolase (FAH). A child inherits the disease from two defective genes, one from each parent. FAH is essential in the metabolism of tyrosine. The absence of FAH leads to a build up of toxic metabolic products in the body, which will result in liver and kidney damage. Tyrosinemia is diagnosed by a blood and urine test.
Tyrosinemia is treated by a low protein diet (low in phenylalanine, methioonine and tyrosine) and a drug called NTCB. This drug is an inhibitor that blocks the metabolism of phenylalanine and tyrosine. Although the drug is not a cure, it manages the disease. …