The gastrointestinal tract and liver play key roles in the digestion, absorption and metabolism of nutrients. Diseases of the gastrointestinal tract and liver may profoundly disturb normal nutrition. Malabsorption refers to decreased intestinal absorption of carbohydrate, protein, fat, minerals or vitamins. There are many symptoms associated with malabsorption. Weight loss, diarrhea, greasy stools (due to high fat content), abdominal bloating and gas are suggestive of malabsorption.