Vitamin D instructs the intestines to absorb calcium. Without calcium and vitamin D, bones weaken and become susceptible to fractures. Vitamin D is a fat-soluble vitamin. Thus, people who have a deficiency in this vitamin and have fat in their stool have a malabsorption of fats.
Vitamins A, K, E and D are the fat-soluble vitamins, which means these vitamins need fat so the cells of the small intestines can absorb them, according to Kim Barrett, Ph.D., in “Gastrointestinal Physiology.” If problems exist with fat absorption, none of the fat-soluble vitamins can be absorbed and used by the cells. As a result, people acquire vitamin deficiencies and show symptoms of deficiency. Fat in the stool is one of the symptoms.
Short Bowel Syndrome
Short bowel syndrome describes the symptoms of malabsorption when the small intestines are shorter than normal. This usually happens as a result of surgery, when part of it must be removed due to a congenital disorder, disease, cancer or damage from lack of oxygen. The liver makes bile to help break down fats and the bile acids are absorbed in the ileum, or last part of the small intestines, explains Atenodoro Ruiz, Jr., M.D., a gastroenterologist at Kaiser-Permanente, in “The Merck Manual for Healthcare Professionals.” Removing more than 100 cm results in the malabsorption of bile acids and, therefore, the malabsorption of both fat and fat-soluble vitamins.
Deficiency of Pancreatic Enzymes
The pancreas makes enzymes, including one called lipase that digests fats into monoglycerides and free fatty acids in the small intestines, explains Elizabeth Corwin, Ph.D. in “Handbook of Pathophysiology.” People who do not have enough pancreatic lipase, cannot digest fats, resulting in the malabsorption of fat-soluble vitamins, including vitamin D. It usually happens in cystic fibrosis and chronic pancreatitis, or the long-term inflammation of the pancreas.
Congenital Lipase Deficiency
In “Gastrointestinal Physiology,” Kim Barrett, Ph.D. writes about a rare disorder where some children are born without enough of the pancreatic lipase enzyme. Their small intestines cannot fully absorb or break down fats, or completely absorb vitamin D and the other fat-soluble vitamins. As children, they will have smelly, fatty stools. They usually have enough lipase so they do not have any other symptoms of fat-soluble vitamin deficiencies. For those children who do have other symptoms, they have other problems that are interfering with fat absorption.
Vitamin D Deficiency
People who have steatorrhea, or fat in their stool, and a vitamin D deficiency have a malabsorption of fats. The fats are not being absorbed and they are trapping vitamins A, K, E and D. This causes the deficiency. The most common symptom is a long-lasting, fatty diarrhea, according to Ruiz in “The Merck Manual for Healthcare Professionals.”
People with a severe vitamin D deficiency may have fractures and pain in their bones.