Definitional Considerations

In its broadest context, malnutrition is a state of having an inappropriate nutritional status with respect to one or more macronutrient (water, electrolyte, protein, or fat) or micronutrient (vitamin or mineral) constituent of the body. This imbalance can be a deficit, leading to an insufficient supply or content of the nutrient (undernutrition), or an excess, leading to an excessive content or overloading of the organism with a nutrient (overnutrition).

Victor Herbert enumerated six possible causes for all nutrient deficiencies as: decreased intake; impaired absorption; increased wastage; impaired utilization; increased destruction; and elevated requirements. Correspondingly, with the exception of any utilization defect, overnutrition and excesses can result from the reciprocal defects, that is: hyperphagia; hyperabsorption; increased retention; decreased destruction; and decreased requirements.

As discussed in the previous chapter, the term 'primary' malnutrition relates almost exclusively to the first of these mechanisms, that of the ingestion of nutrients from the diet. It is about food consumption and intake. Secondary malnutrition, by contrast, concerns the disturbed and disordered handling of nutrients. When diseases or abnormal physiological conditions interfere with the normal disposition of nutrients ingested from the diet, this is the basis of a situation of 'secondary' malnutrition. A representative, but not exhaustive, list of diseases and conditions producing secondary undernutrition is provided in Table 1. The roster of causes of secondary overnutrition is provided in Table 2.

The basis for suspecting the presence of secondary undernutrition emerges when there is evidence of malnutrition (deficiency or excess) but food and nutrients are presumably being consumed with in abundance. Once the suspicion emerges, three distinct diagnostic principles need to be addressed: (1) the confirmation of dietary intake, and estimation of its adequacy; (2) the diagnosis and classification of abnormal nutritional status; and (3) the diagnosis of the functional, physiological, or pathological origins of disordered nutrient disposition. To emphasize the

Table 1 Diseases and conditions associated with secondary macronutrient or micronutrient undernutrition

Decreased nutrient absorption

Gastric atrophy Pernicious anemia Celiac disease Inflammatory bowel disease Intestinal cryptosporidiasis Pancreatic insufficiency Biliary obstruction Cystic fibrosis Radiation enteritis

Chronic intestinal pseudoobstruction Increased nutrient excretion

Hepatic cirrhosis

Laxative abuse

Peptic ulcer

Gastrointestinal fistula

Gastric adenoma

Colonic adenoma

Amebiasis

Hookworm

Schistosomiasis

Diabetes mellitus

Fanconi syndrome

Hypoaldosteronism

Hemodialysis; peritoneal dialysis

Increased destruction or internal consumption nutrients

Hyperthyroidism

Cardiac cachexia

HIV/AIDS

Cancer cachexia

Cystic fibrosis

Bone marrow transplants

Pulmonary tuberculosis

Decreased utilization of nutrients

Lead poisoning

Menkes' copper storage disease point, one must remain attuned to the nutritional status of patients, clients, or populations, and sensitive to the possibility of a nonprimary origin of any under- or overnutrition.

Table 2 Diseases and conditions associated with secondary macronutrient or micronutrient excess (overnutrition)

Increased nutrition absorption

Wilson's disease Hemochromatosis

Increased nutrition retention

Prader-Willi syndrome Hypercorticosterism Hyperpituitarism Acute tubular necrosis Chronic renal failure

Decreased destruction of nutrients

Hypothyroidism

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