FOLATE DEFICIENCY SECONDARY TO DISEASE OF THE INTESTINAL TRACT
Posted Sep 11 2009 4:57pm
BY FREDERICK A. KLIPSTEIN
MALABSORPTION from the intestinal tract is a common cause of deficiency of folate and vitamin B12. Deficiency of either of these vitamins results in the development of a megaloblastic anemia. Vitamin B12 is particularly susceptible to defects of absorption since it requires the elaboration of intrinsic factor from the stomach to facilitate its absorption and must traverse the length of the small intestine to reach its specific absorption site, the ileum.' Thus defects in intrinsic factor production, the presence in the upper small intestine of parasitic or bacterial organisms that utilize the vitamin, or disease of the ileum can all result in malabsorption of vitamin B12. In the United States, with the exception of rare dietary deficiency occurring in vegetarians, deficiency of vitamin B12 is always a secondary manifestation of disease of the gastrointestinal tract. Folate is absorbed principally in the proximal jejunum' and disorders of folate absorption are associated with disease of this segment of the intestine.
In addition to malabsorption, folate deficiency can also result from inadequate dietary intake, from excessive demand, as sometimes occurs in pregnancy or hemolytic anemia, or secondary to the use of folic acid antagonists or anticonvulsant drugs. Although some disorders of the intestinal tract can be associated with malabsorption and deficiencies of both folate and vitamin B12, this review will restrict itself to a consideration of malabsorption and deficiency of folate.