A 69-year-old man is given a multivitamin containing vitamin B12. He feels well, reports no symptoms, and his physical examination is normal. His CBC is completely normal. Which of the following is most characteristic of vitamin B12 absorption?
Vitamin B12 absorption is best in the distal ileum. Receptors for the intrinsic factor are present in the distal ileum, but mass action absorption also occurs with large doses. However, the oral route is still felt to be unreliable if hematologic or neurologic effects are present. The Schilling test, with and without intrinsic factor, can help diagnose the exact cause of B12 deficiency.
totally dependent on the intrinsic factor
best in the duodenum
improved in folic acid deficiency
best in the distal ileum
G.I.T.