New findings indicate that use of proton pump inhibitors and histamine 2 receptor antagonists is linked to vitamin B12 deficiency.

These medications both have an acid-inhibiting effect, and are widely taken for excess stomach acid. However, concerns have been raised that because they suppress the production of gastric acid, they can cause problems absorbing vitamin B12.

To investigate long-term exposure to these drugs and vitamin B12 deficiency, a team led by Dr Jameson Lam of Kaiser Permanente, California, USA, carried out a large population-based study.

They compared 25,956 patients with vitamin B12 deficiency between January 1997 and June 2011 and 184,199 patients without, using figures from electronic pharmacy, laboratory, and diagnostic databases.

Being prescribed proton pump inhibitors for two or more years was linked to a 65% higher chance of vitamin B12 deficiency. Two or more years of histamine 2 receptor antagonists were linked to a 25% raised risk.

In addition, higher doses of proton pump inhibitors were associated with a higher risk. Doses of more than 1.5 pills per day were more risky than doses less than 0.75 pills per day. Full details appear in the Journal of the American Medical Association today (11 December).

“Previous and current gastric acid inhibitor use was significantly associated with the presence of vitamin B12 deficiency,” warn the authors. “These findings should be considered when balancing the risks and benefits of using these medications.”

They add that: “Vitamin B12 deficiency is relatively common, especially among older adults; it has potentially serious medical complications if undiagnosed. Left untreated, vitamin B12 deficiency can lead to dementia, neurologic damage, anaemia, and other complications, which may be irreversible.”

Lam, J. R. et al. Proton Pump Inhibitor and Histamine 2 Receptor Antagonist Use and Vitamin B Deficiency. JAMA 11 December 2013 doi:10.1001/jama.2013.280490