Appendix: Ways to Get B12 Deficiency
(Reference: Herbert1 where not otherwise noted.)
- Inadequate dietary intake.
- Inadequate absorption:
- Pernicious anemia - Problems with intrinsic factor.
- Loss of intrinsic factor: Genetically predetermined and age-dependent (sometimes as early as 45 yrs). The most common cause of B12 deficiency in non-edlerly, nonvegetarians.
- Autoimmunity to intrinsic factor: Circulating antibodies to intrinsic factor indicate eventual pernicious anemia if not treated. A chronic B12 deficiency damages immune function and the antibodies may disappear as B12 deficiency progresses.
- Food-cobalamin malabsorption - Loss of gastric acid and/or protein digesting enzymes which break the protein-B12 bonds in food. This can be caused by stomach surgery, atrophy or inflammation of the stomach, medications that suppress acid secretion, or a stomach infection by H. pylori or anaerobic bacteria (which can be due to low stomach acid).2
- Pancreatic disease reduces free calcium in the ileum (calcium is needed for B12 absorption). Can be improved with calcium and/or bicarbonate.
- Unhealthy ileum.
- Drugs decreasing absorption include cimetidine, metformin (ties up free calcium in intestines), potassium chloride, and cholestyramine.3
- Infection by tapeworms,4Diphyllobothrium latum,5 or Giardia lamblia.3
- Defects in B12 enzymes, transport proteins, or storage proteins.
- Defects in B12 enzymes that result in high MMA levels are rare. One researcher reported that they occur in 1 out of 28,000 people.6 Ciani et al.6 provide an informative diagram showing which enzymes are involved in the various B12 metabolic pathway defects.
- Increased requirement during pregnancy or hyperthyroidism.
- Increased excretion caused by alcoholism.
- Nitrous oxide anesthesia in people with low serum B12 (nitrous oxide can change the cobalt atom of B12).4
- Hypothyroidism (possibly autoimmune).7
- AIDS can cause B12 deficiency as shown through macrocytic anemia and neurological problems without elevated homocysteine levels.
| Notes for Appendix: Ways to Get B12 Deficiency |
| 1. Herbert V. Staging vitamin B-12 (cobalamin) status in vegetarians. Am J Clin Nutr. 1994 May;59(5 Suppl):1213S-1222S. |
| 2. Ho C, Kauwell GP, Bailey LB. Practitioners' guide to meeting the vitamin B-12 recommended dietary allowance for people aged 51 years and older. J Am Diet Assoc. 1999 Jun;99(6):725-7. |
| 3. Tucker KL, Rich S, Rosenberg I, Jacques P, Dallal G, Wilson PW, Selhub J. Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring study. Am J Clin Nutr. 2000 Feb;71(2):514-22. |
| 4. Groff J, Gropper S. Advanced Nutrition and Human Metabolism, 3rd ed. Wadsworth: 2000. |
| 5. Halsted JA, Carroll J, Rubert S. Serum and tissue concentration of vitamin B12 in certain pathologic states. N Engl J Med. 1959;260:575-80. |
| 6. Ciani F, Poggi GM, Pasquini E, Donati MA, Zammarchi E. Prolonged exclusive breast-feeding from vegan mother causing an acute onset of isolated methylmalonic aciduria due to a mild mutase deficiency. Clin Nutr. 2000 Apr;19(2):137-9. |
| 7. Johnson PR Jr, Roloff JS. Vitamin B12 deficiency in an infant strictly breast-fed by a mother with latent pernicious anemia. J Pediatr. 1982 Jun;100(6):917-9. |