Medical Edge Newspaper Column

Pernicious Anemia And Vitamin B12

Oct. 23, 2006
DEAR MAYO CLINIC:
I have been diagnosed with pernicious anemia. It was not discovered until I had nerve damage. I am taking Vitamin B12 shots, but I wonder if exercise or a certain diet would be helpful. -- Waite Park, Minn.

ANSWER:
Exercise and a healthy diet almost always benefit your general health, but they probably won't affect pernicious anemia, which is due to vitamin B12 (cyanocobalamin) deficiency. The only exception to this is if you are a strict vegan and eat no animal products, since the only significant sources of vitamin B12 in the diet are animal-derived products. The body is able to store several years' worth of vitamin B12, so it's very rare that pernicious anemia is caused by diet alone.

If you are a vegan, broadening your diet to include chicken, eggs, fish, shellfish or dairy products -- all sources of vitamin B12 -- could be beneficial. It doesn't take much in the way of animal-based foods to make a difference. Even ketchup -- with the bugs that stick to an occasional tomato -- contains some vitamin B12.

Exercise -- more or less of it -- won't affect pernicious anemia. It might be hard to exercise right now if you are quite anemic, but that should improve as your body responds to the vitamin B12 shots that you are getting. Exercises focused on improving your sense of balance may help if nerve damage has caused you to be unsteady while walking.

Most of the time, pernicious anemia is related to an autoimmune problem involving the gut that prevents absorption of vitamin B12. Stomach or bowel resection surgery can also contribute to pernicious anemia. As a result of surgery, there may not be enough area inside the bowels to absorb adequate vitamin B12, which is an essential vitamin for production of blood cells and maintenance of nerve health.

Rarely, pernicious anemia can also be caused by certain tapeworms found in raw fish or by bacterial overgrowth in the intestines. Finally, inhaling large amounts of nitrous oxide (laughing gas) can destroy vitamin B12 and lead to rapid development of B12 deficiency.

Vitamin B12 deficiency can cause nerve damage, as you mentioned. The nerve damage in patients with B12 deficiency most commonly results in difficulty sensing vibration, balance problems due to the inability to sense the position of the limbs, and numbness or tingling of the fingers and toes. Even after starting vitamin B12 supplementation, the injured nerves may not fully recover. In that situation, you need to be especially careful to avoid stumbling and hurting yourself.

Generally, pernicious anemia is easy to treat with vitamin B12 injections. More recent studies suggest that many patients will also respond to large doses of vitamin B12 by mouth, and may not need injections. Early treatment will help prevent further nerve damage.

-- David Steensma, M.D., Hematology, Mayo Clinic, Rochester, Minn.