Caring for the Cancer patient: Causes of Anorexia in Cancer.

Anorexia in cancer is either a loss of appetite or decreased caloric intake. It is a significant component of cancer cachexia. Multiple causes of anorexia exist in cancer:

Peripheral causes

·         Cancer tumours may cause difficulty in food swallowing, leading to inadequate nutrient intake.

·         Some tumours can secrete substances such as tryptophan, parathormone-related peptide3 or lactate, which alter food intake.

·         Other tumours may alter nutrients such as zinc, resulting in anorexia. 

·         Tumours can cause inflammation in the body, leading to anorexia. Inflammation can cause a loss of appetite, fatigue, and weakness.

·         Tumours in the stomach or intestines can cause a feeling of fullness or bloating, making it difficult for a person to eat.

·         A cancer diagnosis's emotional and psychological impact can also contribute to anorexia. Fear, anxiety, and depression can all lead to a loss of appetite and a reduced interest in food.

·         Altered GI functioning can alter visceral receptor function leading to altered secretion of gastrointestinal peptides, e.g. peptide tyrosine (PYY), and alterations in stomach emptying can alter feedback of satiating hormones.

·         Some tumours can affect a person's sense of taste and smell. This can lead to a loss of interest in food or cause certain foods to taste unpleasant.

·         Cancer treatments such as chemotherapy, radiation therapy, and surgery can cause various side effects that can lead to loss of appetite and anorexia. For example, chemotherapy and radiation can cause nausea, vomiting, and changes in taste and smell, all contributing to losing appetite.

Central causes

Cancer patients may easily slide into depression, reflected by various alterations in central neurotransmitters. Alterations In serotonin and corticotrophin-releasing factor(CRF)  are some of the changes in depression that may lead to anorexia. When cancer patients are given IV interferons, kynurenine/kynurenic acid(linked to depression and anorexia) increases remarkably. Sickness behaviour often observed in cancer patients results from pro-inflammatory cytokines. It is characterized by general body weakness, melancholia, lack of motivation, sleepiness, lack of concentration, hyperalgesia and anorexia. Hypoxia has been shown to cause anorexia in head and neck cancer patients.