After a child in diagnosed with an IEM that requires treatment with Medical Foods, the metabolic limitations and dietary requirements of the patients are first established based on the specific diagnosis and dietary requirements that support normal growth and development. Medical nutritional therapy is based on the principle that abnormal levels of metabolites in the blood cause serious or lethal complications that can be prevented by normalizing the blood biochemistry through manipulation of specific nutrients in the diet. The diet is crafted so that essential nutrients are provided from natural foods only in the amounts that will not create toxic accumulations of the offending metabolites. For a typical 10 year old child with PKU, this would require restriction to only 5 grams of natural protein which equates to about two slices of bread OR a half cup of milk. The rest of the diet MUST come from the medical foods to provide 1800 calories and 40 grams protein. Low protein medical foods contain negligible
amounts of protein in relation to their calorie content. This type of therapy intervention is a balancing act in which patient choice, cost, availability and insurance coverage all play an integral role. The more choice there is, the more likely that the child and family will adhere to the medical diet. Medical foods are therapeutic agents comparable to any regular drug and should be considered under the same rubric for prescribing and insurance purposes.
Medical foods come in three basic formats:
Types of medical foods
Infant formulas: For over 50 years the main products have used elemental forms of nutrients to make ersatz milk formula substitutes based on the composition of regular milk but lacking the "toxic" ingredients. Such products are ideal for use during infancy. However, a diet exclusively of milk is not feasible for normal adults and such products cannot provide a majority of the nutritional needs of older patients. An additional array of products for older children and adults is essential. These "milks" have been the main constituent in most metabolic diets and some people appear to consider them as the only legitimate form of medical food. This is clearly not the case.
Alternate protein products: As patients grow, infant formulas alone cannot to provide normal nutrition or any semblance of a normal existence. As a result novel formulations have emerged to provide the same essential protein and energy needs for older patients as the formulas do for infants. These include solid and powder forms of critical nutrients, amino acids in a variety of forms and protein free beverage powders that can be compounded into tailor-made diets that are somewhat more acceptable to older children, adolescents and adults. These products also exclude the specific nutrients that are harmful because of the primary diagnosis.
Low protein energy sources and alternate energy products: The above products are, by far, the most costly to manufacture. However, except for infants they are still do not provide adequate amounts of energy. They are designed as the main alternative to natural protein and thus are not suited to provide the total energy requirements. Adequate energy intake is just as important to a balanced diet as the control of the primary underlying metabolic defect. Inadequate energy intake can cause metabolic decompensation that can result in neurological damage just as severe as if treatment had never been started. Low protein substitute products come in the form of baking mixes, pastas, rice, sauces and pre-made items that are designed to be as similar to their normal counterparts as possible but yet supply negligible protein They become essential sources of energy, satiety and organoleptic satisfaction and markedly increase the chances of patient acceptance and compliance.
For other metabolic disorders, alternate energy sources are essential for preventing catabolism in order to avoid metabolic complications. An example is the inclusion of medium chain triglycerides in diet therapy which comes in the form of oil or powdered sachets with the addition of protein for the treatment of Fatty Acid Oxidation disorders.