Vitamin B12 Deficiency: Causes, Evaluation and Treatment

Vitamin B12 (cobalamin) deficiency is a major public health problem, particularly among the elderly population. It is known that a deficiency in serum B12 levels can cause a combination of neurological and psychiatric disorders. Therefore, in these cases successful replacement of depleted B12 levels is a necessity. Identification of B12 deficiency in elderly patients can be rather difficult as they often tend to present with neurological and neuropsychiatric symptoms despite a lack of haematological evidence showing depleted serum B12 levels. More recently, other parameters such as methylmalonyl-CoA or homocysteine (components of the cobalamin-dependent pathways) have been used as markers of B12 deficiency. Both parameters become elevated upon the onset of B12 deficiency. Several studies have shown that oral B12 replacement therapy can be equally as effective as parenteral (intra-muscular) B12 replacement. Yet, despite these publications, B12 is primarily administered to deficient patients intramuscularly. This inconvenient method of B12 replacement places a rather unnecessary demand on healthcare resources. Clinical Points: •Deficiency of serum vitamin B12 levels can cause a variety of neurological and psychiatric disorders. •Vitamin B12 deficiency has been reported in approximately 15% of adults older than 65 years of age. This is believed to be mainly caused by an age-related decline in intestinal absorption. •Approximately 98% of B12 absorption is facilitated by intrinsic factor. The remaining 2% is absorbed passively. •Oral B12 supplementation in high doses has been found to be as effective as intra-muscular vitamin B12 administration in pernicious anaemia. •Intra-muscular B12 remains the treatment of choice in most Western countries, contrary to the prevailing evidence. TSMJ Vol. 9 2008