Anorexia as a general effect of cancer

Anorexia is a frequent problem in cancer patients and is a major determinant of cancer cachexia. Anorexia can be analyzed in the context of normal food intake control mechanisms and changes in these mechanisms observed in cancer patients. Two major determinants of normal food intake control are: 1) chemo‐receptors located within the ingestive apparatus which serve a gating and motivational or excitatory role and 2) the affects of accumulation of ingested substances in the intestinal tract which tend to counteract the excitatory effects of gustatory stimulation and thus result in an inhibition of food intake. Stimuli from the chemoreceptor system and the intestinal volume receptor system are integrated within the central nervous system. Studies in cancer patients have delineated changes in taste and smell sensation which blunt the normal excitatory stimuli from food intake. Patient symptoms and observations in an animal model suggest alterations within the gastrointestinal tract which may also negatively influence food intake in the cancer patient. Food intake is also influenced by glucosensitive receptors and amino‐acid‐sensitive receptors, and alterations in glucose metabolism and in profiles of amino acids may negatively influence food intake in the cancer patient. Since all of these cues are integrated within the central nervous system, it is likely that different aberrations may be determinants of anorexia in different patients and that patients with the most severe degrees of anorexia may be suffering from aberrations of multiple cues for food intake. Selection of food which has a flavor and odor which may appeal to the patient with altered chemoreceptors, and selection of food requiring minimum mechanical and digestive activity within the intestinal tract may be of value in ameliorating anorexia.