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Why can chronic illnesses such as cancer or AIDS cause malnutrition?

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rickets, a nutritional disease — nutritional disease Children with rickets. The disease, which most commonly strikes children, causes bone deformities such as bowlegs. Rickets is caused by a lack of vitamin D or calcium.

Chronic illnesses such as cancer or AIDS can lead to malnutrition through several physiological mechanisms that interfere with the body's ability to obtain or utilize necessary nutrients.1

Reduced Appetite: Sickness and the systemic effects of chronic disease often contribute to a poor appetite, resulting in inadequate food consumption.1
Metabolic and Digestive Interference: Malnutrition can arise from acquired metabolic defects that prevent the proper digestion, absorption, and metabolism of foodstuffs by organs and tissues. Diseases affecting the gastrointestinal tract can reduce the absorptive function of the bowel, while conditions involving severe, prolonged vomiting or diarrhea can lead to increased losses of essential nutrients.12
Increased Nutritional Requirements: Chronic conditions may increase the body's requirements for specific nutrients. If the diet is not adjusted to meet these heightened demands, deficiencies can develop.2
Treatment Side Effects: The management of chronic illnesses, including the administration of various drugs or certain surgical procedures, can artificially manipulate the body’s natural metabolic pathways, potentially leading to further nutritional deficiencies.2

Ultimately, malnutrition in these contexts is a complex result of the body's inability to maintain a sufficient supply of nutrients due to these combined physical and metabolic challenges.1