Do Intestinal Problems Cause A Vitamin B-12 Deficiency?

Vitamin B-12, or cobalamin, is a member of the B-complex family. Even though it is water soluble -- excess intake is easily eliminated in your urine -- your liver stores enough vitamin B-12 to last for up to six years, according to "The Merck Manual of Diagnosis and Therapy." Vitamin B-12 is the only vitamin that contains an essential mineral -- cobalt -- and it possesses the most complex molecular structure of all vitamins. Absorption of food-based vitamin B-12 involves a coordinated series of intestinal events.

Absorption

Vitamin B-12 must first be liberated from foods through the actions of gastric acid, which is secreted by parietal cells in your stomach lining. Once freed, B-12 is quickly bound by R proteins -- another product of the cells lining your stomach -- which transport vitamin B-12 into your small intestine. Pancreatic enzymes in the upper part of your small intestine cleave R proteins from vitamin B-12, which is immediately recaptured by intrinsic factor, yet another protein secreted by your gastric parietal cells. The intrinsic factor-B12 complex, or IF-B12, is eventually absorbed when it binds to special receptors in the lower end of your small intestine.

Malabsorption

A number of intestinal problems can interrupt vitamin B-12 processing and prevent its absorption into your bloodstream. If your stomach stops producing acid or intrinsic factor -- common occurrences in older people, in people taking certain ulcer medications and in a condition called pernicious anemia -- vitamin B-12 is not efficiently liberated from your foods or absorbed through your lower intestine. Other conditions, such as Crohn's disease and celiac disease, interfere with the uptake of IF-B12. The January 2011 issue of "The New England Journal of Medicine" describes genetic disorders that alter the IF-B12 receptors in your intestinal wall and prevent B-12 absorption.

Deficiency

Because vitamin B-12 is stored and recycled by your liver and intestine, a decrease in B-12 absorption does not immediately lead to deficiency. Rather, vitamin B-12 deficiency develops over many months to years. Symptoms include fatigue, weakness, altered sensation in your extremities, decreased or abnormal reflexes, difficulties with balance and walking, confusion, dementia and paranoia. Anemia characterized by abnormally large and poorly functional red blood cells is a common sign of B-12 deficiency. If untreated, vitamin B-12 deficiency can result in irreversible nerve damage and death.

Considerations

Vitamin B-12 is only found in appreciable amounts in animal-based foods and in supplements. B-12 absorption from foods is complex and requires a healthy gastrointestinal tract. Fortunately, oral supplementation with vitamin B-12 maintains sufficient tissue levels of this important nutrient. Supplement-based B-12 is more efficiently absorbed than food-based B-12, and the doses in supplements are large enough to overcome absorption problems through "mass action." According to the National Institutes of Health Office of Dietary Supplements, dietary recommendations for vitamin B-12 vary from 0.4 mcg daily for infants to 2.8 mcg for nursing mothers. Ask your doctor if you need additional vitamin B-12.