Malabsorption is a condition caused by the decreased ability to digest and/or absorb nutrients from food. It is seen with a variety of diseases and can lead to general malnutrition or to symptoms associated with deficiencies in specific nutrients.
The body requires a steady supply of nutrients to build, repair, and maintain itself, to produce energy, enzymes, hormones, proteins, cells, tissues and bone, and to fight infections. Nutrients come from the diet and include many essential vitamins and minerals (micronutrients).
Food that is eaten is digested in three stages:
- Proteins, fats, and complex sugars (carbohydrates) are broken down by stomach acids, enzymes produced by the pancreas, and bile from the liver. This process also releases micronutrients.
- Nutrients are absorbed primarily by cells in the small intestines.
- Nutrients are transported throughout the body and used or stored.
Any disruption or interference with this process can lead to malabsorption. The type and severity of deficiencies seen and the symptoms experienced depend on whether the problem affects general digestion and absorption or affects one or more specific nutrient.
Fat, proteins and carbohydrates cannot be properly digested without bile and pancreatic enzymes. Insufficiencies in these substances can occur, for example, with liver and pancreatic diseases that limit their production, and with conditions such as cystic fibrosis that prevent pancreatic enzymes from getting to the digestive tract.
If the intestines are unable to or prevented from absorbing nutrients, then the nutrients are eliminated from the body in the stool. This can happen when there is damage to the intestinal cells and tissues or when the intestines have been shortened, such as due to surgery, reducing the surface area and the amount of time available in which nutrients can be absorbed from food as it passes through the digestive tract.
As an example of a specific deficiency, vitamin B12 absorption requires both stomach acid and intrinsic factor, a substance produced by parietal cells in the stomach. Stomach acid separates B12 from proteins and intrinsic factor binds with B12. A lack of either one prevents intestinal absorption and can lead to vitamin B12 deficiency. This can happen with advancing age, with medications that suppress stomach acid production, with gastric bypass surgeries, and with diseases that damage parietal cells or cause general malabsorption.
Once absorbed in the intestines, nutrients may be hindered from being transported throughout the body. This may be caused by problems with the lymphatic system such as lymphoma or the rare inherited disorder, abetalipoproteinemia.