Malabsorption is the inability of the body to absorb nutrients from food. A number of disorders involve malabsorption. Some are well-defined diseases whereas others are collections of related symptoms. They may all be referred to as malabsorption syndromes.

Normal digestion begins with the chemical breakdown of food in the stomach. These smaller particles of food then pass into the small intestine, where most nutrient absorption occurs. Food particles are further broken down into nutrients such as carbohydrates, fats, protein, vitamins and minerals that can be absorbed through the intestinal walls into the blood. The nutrients are then carried, via the bloodstream, to cells throughout the body for nourishment and energy. Remaining waste travels through the large intestine and exits the body as stool.  

The structure of the small intestine allows for maximum absorption. The many intestinal folds and the projection of villi (fingerlike) and microvilli within the intestinal lining create a large combined surface area. This results in the greatest exposure of nutrients to digestive enzymes.

Malabsorption occurs when any part of the process within the small intestine is interrupted. This may involve impairment in one or more of the following phases of the process:

• Digestion. The chemical breakdown of food particles in the small intestine. The pancreas, bile ducts, liver and gallbladder all play a role in the production of enzymes and bile that help break down food particles into nutrients the body can use. Digestion is regulated by hormones and nerves. Impairment of any of these digestive components can lead to malabsorption.
  

  

• Absorption involving intestinal lining. The mucosal (mucous) lining of the small intestine absorbs and secretes substances during digestion. Problems or abnormalities in the lining of the small intestine can cause malabsorption. Celiac disease is the most common cause of impaired absorption.
  
  
• Transport of nutrients into the bloodstream. The movement of fats and proteins into the bloodstream from the small intestine. When lymph vessels within the small intestine become enlarged or obstructed, nutrients are unable to be carried into the bloodstream for circulation throughout the body. Problems with lymph vessels, such as intestinal lymphangiectasia, may cause this nutrient malabsorption.

Malabsorption may involve the inability to absorb all nutrients (e.g., carbohydrates, fats, protein, vitamins and minerals) or just specific ones.

Malabsorption may occur in:

• Isolated areas of the small intestine due to impaired digestion (e.g., problems absorbing specific nutrients)
  
  
• Throughout the entire small intestine due to conditions that impair absorption abilities (e.g., Celiac disease).  

Untreated, malabsorption can lead to a number of health problems and complications, including malnutrition, vitamin deficiencies, osteoporosis (loss of bone density) and stunted growth or development in children.