Nutritional and digestive disorders

Because the gut is constantly exposed to what we eat and drink, it is vulnerable to infection, poor diet and mechanical strain, and this produces a wide range of disorders. Bacterial, viral or parasitic infection of the intestinal lining can cause colitis, marked by rectal bleeding, abdominal cramps and diarrhoea. In growing children, an inadequate protein diet can cause protein-energy malnutrition (PEM), seen as two related conditions — Marasmus, an acute form caused by a diet lacking both carbohydrate and protein, leaving children emaciated with thin, wasted muscle and fat, dry folded skin and diarrhoea; and Kwashiorkor, marked by a pot-belly and facial oedema, dry skin, stunted growth, hair-colour changes, and general weakness and irritability. Everyday complaints include indigestion (incomplete digestion causing fullness, from poor enzyme secretion, anxiety, food poisoning, overeating or spicy food), constipation (retained faeces from low dietary fibre and low physical activity), and vomiting, essentially a reverse peristalsis controlled by the vomit centre in the medulla oblongata and usually preceded by nausea. More serious conditions involve the liver and its ducts: jaundice, where a failing liver cannot properly clear bile pigments from the blood, turning the skin and eyes yellow (often triggered by viral hepatitis); liver cirrhosis, a chronic degeneration of liver tissue into scar tissue (fibrosis) caused by infection, poisoning, malnutrition or alcoholism; and gall stones, crystallised cholesterol deposits in the bile that can obstruct the cystic, hepatic or hepato-pancreatic ducts, causing pain, jaundice and pancreatitis. Appendicitis is inflammation of the vermiform appendix, treated by surgical removal since a ruptured appendix can cause peritonitis (infection of the abdominal cavity). Hiatus hernia occurs when the upper stomach protrudes through the diaphragm, commonly causing heartburn as acidic stomach contents travel back into the oesophagus. Diarrhoea, the most common gastrointestinal disorder worldwide, results when pathogens damage the colon lining so it cannot absorb fluid properly, and is managed with oral rehydration therapy. Peptic ulcer is an eroded patch on the stomach or duodenal lining, most often caused by Helicobacter pylori infection (a discovery that won Barry Marshall and Robin Warren the …