Vitamin B-12, or cobalamin, is a member of the B complex family. However, it differs in many respects from other B vitamins. Cobalamin has the most complex chemical structure of all vitamins, and it is the only vitamin that contains an essential mineral -- cobalt. Vitamin B-12's mechanism of absorption is unique and, unlike other B vitamins, cobalamin is stored in your body for months or even years. Protonix and other medications that stop stomach acid production can interfere with vitamin B-12 absorption and can contribute to deficiency in some people.
Absorption
Before food-bound B-12 can be absorbed, it must first be released by pepsin, a stomach enzyme that requires acid for its activation. Once vitamin B-12 is liberated by pepsin, it is "captured" by R proteins secreted from your stomach lining. R proteins carry the B-12 into your small intestine, where pancreatic enzymes remove the R proteins. Freed vitamin B-12 is immediately re-bound to intrinsic factor, a protein secreted by the same stomach cells -- parietal cells -- that produce acid. The intrinsic factor-B-12 complex is eventually absorbed in your lower small intestine through the actions of cellular receptors that specifically recognize the IF-B-12 complex.
Malabsorption
Absorption of food-borne vitamin B-12 can decrease in situations where your stomach's ability to produce acid is impaired. The classic B-12-deficiency disease, pernicious anemia, is caused by autoimmune destruction of your stomach's parietal cells. This leads to a loss of both acid production and intrinsic factor secretion. In a similar fashion, a condition called atrophic gastritis gradually robs many elderly persons of their ability to absorb vitamin B-12. Concerns about the long-term use of anti-ulcer medications, such as Protonix and other proton pump inhibitors, have prompted studies to determine if these drugs can contribute to vitamin B-12 deficiency.
Limited Risk
A review published in the June 2000 issue of "Alimentary Pharmacology and Therapeutics" reported that proton pump therapy did not interfere with vitamin B-12 absorption, except in patients with Zollinger-Ellison syndrome, a disease characterized by marked overproduction of stomach acid. These patients are typically given high doses of proton pump inhibitors for prolonged periods of time. Another review in the May 2010 edition of "World Journal of Gastroenterology" reiterated the possibility of vitamin B-12 deficiency in Zollinger-Ellison patients and voiced similar concerns regarding the use of proton pump inhibitors in the elderly, many of whom are already at risk for B-12 malabsorption.
Considerations
Vitamin B-12 is stored in your body for long periods of time. Therefore, a deficiency is slow to develop, even if you stop absorbing the vitamin altogether. Loss of stomach acid is associated with B-12 deficiencies in several populations of people: individuals with pernicious anemia, elderly persons with atrophic gastritis and Zollinger-Ellison patients on high-dose, long-term proton pump inhibitor therapy. Otherwise, prolonged use of Protonix and similar medications has not been solidly linked to vitamin B-12 deficiencies. To be on the safe side, if you have been taking high doses of Protonix or any other proton pump inhibitor for a long time, ask your doctor if you should have your vitamin B-12 level checked.
References
- Linus Pauling Institute at Oregon State University: Vitamin B12
- "Alimentary Pharmacology and Therapeutics"; Review Article: Potential Gastrointestinal Effects of Long-Term Acid Suppression with Proton Pump Inhibitors; L. Laine, et al.; June 2000
- "World Journal of Gastroenterology"; Safety of the Long-Term Use of Proton Pump Inhibitors; A.B.R. Thomson, et al.; May 2010
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