Nutritional therapy can be defined as a therapeutic system in which special diets and nutritional products are prescribed to individuals, with a view to halting, retarding or reversing any damage to that individual’s physiological and biochemical function which may have been caused by any of the following factors:

1-  Food or environmental allergy or intolerance.
2-  Nutritional deficits due to poor diet, special needs or malabsorption.
3-  Toxic overload due to heavy metals or chemicals in the environment,
dysbiosis, poor eliminative ability or poor liver function.

The patient’s nutritional needs are assessed by examination and symptom analysis, and by the use of laboratory investigation. State –of-the-art laboratory tests, developed by specialists in this field, and which measure nutrient- depend enzymes in blood, hair, sweat, white cells and other tissues or fluids are preferred to ordinary blood levels which are well known to be lacking in the sensitivity required to diagnose nutritional deficiency states other than frank scurvy, beri-beri and similar overt diseases.

1-  Food allergy/intolerance :
The role of idiosyncratic food allergy/intolerance in diseases such as irritable bowel syndrome, migraine, urticaria and rheumatoid arthritis is now widely acknowledged in the literature.

2- Nutritional deficits:
Earlier this century, nutritional investigations were restricted to specific clinical pictures such as that of scurvy. Lately there has been an explosion of interest in the role of the so-called sub-clinical nutritional deficiency states in the onset and /or promotion of diseases as diverse as Aids, Schizophrenia, birth defects and acne.

Official indicators of adequacy ( RDAs and DRVs) are not designed to represent optimal values ,but intakes which healthy groups of people should find adequate to prevent overt deficiency disease. They are not intended to make any allowance for additional needs due to infection, disorders of the gastrointestimal tract or metabolic abnormalities . These limitations are recognized by COMA.

Bearing in mind:
 The greatwealth of research in which nutrient repletion (by supplementation) has resulted in the reversal of diverse chronic disease states hitherto not known to be associated with nutritional deficiency , and toxic metals in hair samples have been linked with delinquent behavior in adults.

 The equally great wealth of research revealing that individuals who eat a nutrient-poor diet high in sugar and fat have consistently higher rates of heart disease, cancers, cataracts and other diseases , than those consuming diets rich in fruits and vegetables, routine investigations into nutritional status seem warranted for most patients at risk of or suffering from chronic diseases.

Many biochemical pathways may be disrupted when the intake or absorptions of a nutrient or nutrients is inadequate or when utilization and/or excretion are increased. As organ reserves become depleted, the ultimate result in the long term may be multiple functional insufficiencies which affect the immune, nervous or detoxification systems, and promote the onset of disease states. While some success has been obtained in preventing or reversing a number of diseases using single nutrients for instance neural tube defects with folic acid, and premenstrual syndrome (PMX)vitamin B6 the success of such treatments may well be ‘hit or miss’ unless the individual patient’s nutritional status is first investigated which test methods capable of detecting a functional deficiency.      

3-  Toxic overload:
Little research has been done to identify links between endo-and exotoxic exposure and common chronic diseases. Some notable exceptions are multiple selerosis and parkinsonism, where results have been variable .The outcome of the functional impairment which can be caused by toxic damage is often so similar to conditions diagnosed as neurological diseases or chronic  fatigue syndrome for instance, that this lack of research is lamentable in the face of such a promising avenue of investigation. It is probably explained by the relative lack of commercial potential for the appropriate treatments .The research that is available notably links hyperactivity disorder in children with excess environmental lead. Likewise, elevated levels of toxic metals in hair samples have been linked with delinquent behavior in adults.

    Nutritional counseling can help reduce the intake and absorption of toxic metals into the body, for example by advocating a diet high in calcium and selenium, which compete with lead and mercury for absorption and uptake into cellular systems. Nutrients such as mentioning, magnesium, taurine and antioxidants play an important role in the biotransformation of endo- and exotoxins, and clinical practice suggests that an increased supply of such nutrients may considerably aid the process. In time resulting in the loss of associated symptoms .Such symptoms may be not only due to the toxic over load it self , but to the nutritional deficits induced as a result  of the over-use of nutrients for detoxification processes , leaving a relative lack of these nutrients for other metabolic functions .

Functional nutrient deficits can also be induced by the impermanent of cellular nutrient uptake mechanisms as a result of the presence of excess levels of undo – of serotoxins.

 The therapeutic trial:
If the nutritional therapist believes, on trhe basis of the available literature, the therapists experience and the patient’s history , symptoms and diet that the patient is suffering from a food intendance

Toxic overland or nutritional therapist will normally prescribe an intervention program in the form are of a therapist will normally prescribe as described above. Then the nutritional therapist will normally prescribe an intervention programmed in the form of a therapeutic trial this is justified by the fact that such programs are non –toxic. Low in cost and most patients in the author’s experience find them acceptable in the short term if the rationale is fully explained.

The intervention consists of nutritional health education, a short-term diet and, if necessary, a course of dietary supplements.

The response to the therapeutre trials normally supports or refutes the diagnosis. If a presence is obtained the patient and therapist then work together to modify the programmer so that minimum intervention is required be achieve or maintain the desired therapeutic effects.