Effect of vitamin B12 and folic acid deficiency on small intestinal absorption.

Three patients are described, and they provide further evidence that deficiency of folic acid and vitamin B(12) may sometimes affect small intestinal function. Malabsorption of both xylose and vitamin B(12) returned to normal in one patient after treatment of a megaloblastic anaemia due to dietary deficiency of folic acid. Impaired absorption of vitamin B(12) was corrected by vitamin B(12) therapy in the other two patients. The initial cause of the vitamin B(12) deficiency in one patient was not apparent, but she was taking Gynovlar 21, which may have been an aetiological factor. In the third patient the small intestinal defect was secondary to pernicious anaemia, and in a group of 98 other patients with pernicious anaemia intrinsic factor did not improve vitamin B(12) absorption in six, and only partially corrected absorption in 30. The significance of these observations is discussed.