The concept of m. it has been further investigated and re-examined in the context of an extensive meaning that includes all the functional, anatomical-pathological, weight, and auxological biochemical alterations induced by quantitatively and qualitatively incongruous food intakes or by morbid conditions that hinder the normal use of nutritional factors.
According to a very widespread (albeit schematic and moreover not univocally understood) etiological classification, forms of m are distinguished. primitive (either by default: undernutrition or undernutrition; or by excess: hyper nutrition or supernutrition ), directly connected to the quantity and quality of food intake, and forms of m. secondary (which can also be by default or, more rarely, by excess), symptomatic of many morbid pictures (or in any case consequential to these).
The m. secondary can coexist with the primary one: for example, a subject already undernourished due to inadequate food intake can be affected by diseases that are in themselves the cause of malnutrition.
The existence of another possibility is sometimes taken into consideration, that of "m. due to imbalance", connected to a marked disharmony of distribution in the food ration, despite the fact that the overall energy intake (provided by carbohydrates, fats, proteins, possibly alcohol) is normal or even excessive. The unbalanced distribution of energy factors (e.g. adequate protein ration with excess fat and low carbohydrate intake) almost always implies a deficiency condition (absolute or more often relative, usually without apparent clinical manifestations), even when the conditions' general characteristics of the subject are apparently prosperous or even marked by obesity. In the latter case, there is, therefore, both an m. caloric excess, as much as an m. by default,
Understood in its broadest sense, the m. is responsible for multiple conditions of organic suffering, which can manifest themselves with overt symptoms (detectable with clinical, anthropometric, laboratory, and possibly radiological findings) or which, much more often, run asymptomatically for a long time ( occult or subclinical disease ), however, impairing the psychophysical efficiency or increasing the morbidity towards certain pathologies, especially degenerative ones.
Examined in its various aspects, the problem of m. primitive transcends its clinical (and moral) implications to also have an extreme economic interest, above all in consideration of the negative repercussions on working capacity, morbidity, and mortality, and therefore on the social costs of these phenomena.
Malnutrition by default
- With the exception of those simple foods which, within certain limits, can be interchanged with others (e.g., for energy purposes, fats can be replaced, within certain limits, with isocaloric quantities of carbohydrates), the deficient supply or the insufficient use of a nutritional factor involves a progressive depletion of its possible reserves in the tissues; therefore a cellular impoverishment, with compromise of some osmotic, enzymatic, and more generally metabolic processes; finally, the onset of cellular and tissue degenerative lesions, some reversible, others irreparable.
While in the initial or occult forms, the diagnosis is possible only through laboratory tests (dosing of the blood contents, and sometimes cellular ones, of vitamins, minerals, proteins, etc.; determination of the nitrogen balance, or other), in the overt forms the diagnosis from the simple collection of clinical and anthropometric data (weight ratio, plyometric values, etc.), even if it needs to be deepened by laboratory research.
Among the many causes in the world that contribute to the persistence of m. primitive by default, those of a socio-economic nature predominate (underdevelopment, hence poverty and subculture, therefore the poor flow of nutritional and health information) and of a geological and ecological nature (this is the case of the endemic goiter due to iodine deficiency, which affects many mountain populations of all the continents). Other significant causes are in relation to contingent or recurring events (such as famines and other natural disasters, long-lasting war events, and the like) or unfavorable cultural influences (restrictive precepts of a religious or philosophical nature; superstitions, prejudices, and food cravings; irrational diets; repeated fasts in protest) or to inadequacies in eating behavior, for various reasons (personal tastes, repulsions or unconscious refusals).
Forms of m. secondary by default are observed in multiple defending pathological conditions: in some endocrine diseases (such as Simmonds's disease and Basedow's disease), psychic, tumoral, metabolic, infectious, and toxic. The latter include iatrogenic avitaminosis from antibiotics (deficiency of vitamins B 2, PP, etc.). In such cases, dietary therapy (oral, tube, or parenteral) plays an adjuvant or non-prominent role, with the exception of various metabolic diseases (see metabolism, congenital diseases of, in this App.; replacement , diseases del, in this App.; dietetics, in this App.), for post-operative conditions (which mainly make use of parenteral nutrition), for dyspeptic syndromes and for intestinal malabsorption (sprue syndromes; enteropathies due to intolerance to gluten, mono- and disaccharides; malabsorption methionine, tryptophan, vitamin B12, folic acid; abetalipoproteinemia, etc.).
Malnutrition by excess.
- The primitive form is widespread in countries with high economic development (see below) and among the privileged classes of depressed countries. It has many metabolic aspects, which will be mentioned later.
The secondary form can be pathological or iatrogenic in nature. In the first case, it usually takes the form of endocrine obesity (from hyperadrenalism, hypothyroidism, diencephalic lesions, etc.) in which, due to the compromised efficiency of some homeostatic mechanisms, a slowing down of the metabolism is determined, among other things. energy, a marked accentuation of anabolic processes, and, therefore, an abnormal hoarding of fat.