Specific malabsorptive states
Lactose Intolerance – Perhaps the most common malabsorptive state is due to lactose malabsorption. This is a genetically determined condition and affects many individuals of African or Asian descent. In these persons, the body lacks an enzyme to digest lactose, a sugar present in milk, and bloating and diarrhea can result. The enzyme may be totally absent or present in reduced amount so that symptoms may vary depending on the amount of lactose ingested. The amount of the enzyme decreases with age and some people first notice symptoms when they reach their twenties.
Dairy products are an important source of calcium and this should be considered in planning diets for lactose-intolerant subjects. Lactose intolerance is widespread and under-diagnosed. Recognizing this condition and using milk treated with enzymes to pre-digest the lactose or taking enzyme tablets with dairy products can correct symptoms related to this condition.
Small intestinal disease – Surgical resection or diseases of the small intestine may result in varying degrees of malabsorption depending on the site of resection or disease.
Diseases involving the duodenum may be associated with lactose intolerance, poor tolerance of concentrated sugars, and decreased absorption of iron and calcium. Almost all nutrients are usually absorbed in the first three to five feet of the bowel. The absorption of most minerals especially iron, calcium and zinc, as well as most vitamins occurs in the upper part of the small intestine.
Resections of the lower parts of the small intestine (ileum) may result from surgical intervention for Crohn’s disease. The ileum plays a major role in reabsorption of bile salts, substances produced by the liver to help digest fats that are recycled by the body for use with future meals. The ileum is also important in vitamin B12 absorption. If bile salts are not absorbed properly, the amount of these substances in bile falls and fats and fat soluble vitamins (A, D, E, K), cannot be properly absorbed. A further problem is that if bile salts reach the colon, they can cause large amounts of fluid to be secreted causing watery diarrhea.
If large portions of the bowel are lost to surgical resection, rapid transit of nutrients through the remaining bowel occurs, causing malabsorption.
Pancreatic disease – Diseases of the pancreas can cause severe malabsorption of fats and carbohydrates. Symptoms depend on the severity of the condition but diarrhea with greasy, foul smelling stools is common and weight loss can be profound.
Liver and biliary disease – In conditions when insufficient bile reaches the intestine, fats are not absorbed and again diarrhea and weight loss occur. Vitamins that are absorbed with fats are also affected and vitamin D deficiency can occur.