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By Sally J. Feltner, MS, PhD
Vitamin B12 is often overlooked as to its importance to human health. Vitamin B12 is needed for the metabolism of another vitamin, folate as well as fatty acids to maintain the insulating layer of myelin surrounding nerve fibers. When myelin degenerates, neurological symptoms occur that include numbness, tingling, memory loss and disorientation. If not treated, it can eventually cause paralysis and death. On the other hand, a deficiency is rare, but can be a public health concern due to marginal B12 status due to either low intake or problems with absorption as often found in the older adult. This deficiency may also occur in people who attempt to practice a strict vegan diet as this vitamin is found almost exclusively in animal products.
The absorption of B12 from food requires adequate levels of stomach acid, intrinsic factor (produced in the stomach) and pancreatic secretions. Even though it is a water-soluble vitamin, the body stores and reuses it more efficiently that it does other water soluble vitamins.
Poor absorption of vitamin B12 can result from a condition called pernicious anemia. It is an autoimmune disease in which the cells in the stomach that produce intrinsic factor are destroyed. Therefore, B12 cannot be absorbed due to a lack of intrinsic factor. The anemia can be treated with injections, nasal gels or oral megadoses. The injections and gel bypass the GI tract and thus there is no need for intrinsic factor. Megadoses can allow adequate amounts of B12 to be absorbed that then do not require intrinsic factor.
Vegan diets are a concern due to B12 found only in animal foods. Severe deficiencies have been found in breast – fed infants of vegan women and marginal deficiencies for all vegans if supplemental or fortified foods are not consumed in the diet.
What You Need to Know – At A Glance
- Helps maintain nerve tissue.
- Aids in reactions that build up protein tissue.
- Needed by normal red blood cell development.
Consequences of deficiency
- Neurological disorders (nervousness, tingling sensations, brain degeneration
- Pernicious anemia
- Elevated blood level of homocysteine (increased cardiac problems)
Consequences of overdose
- None known.
- Excess is excreted by the kidneys and not absorbed.
- B12 injections may cause a temporary feeling of heightened energy.
Primary Food Sources
- Fish, seafood
- Milk and cheese
- Ready to eat cereals
Highlights and Comments
- Older people, those with previous stomach surgery, and vegans are at risk for deficiency.
- Some people become B12 deficient because they are unable to absorb it (pernicious anemia).
- Vitamin B12 is found in animal products and microorganisms only.
Source: Smolin, Lori A. & , Grosvenor, Mary B. Nutrition, Science and Applications, Third Edition
Judith E. Brown, Nutrition Now, 7th Edition