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Certain medications commonly used to treat heartburn may increase the risk of vitamin B12 deficiency, researchers warn.

Researchers from Kaiser Permanente in the US found that long-term use of two acid-suppressing medicines, known as proton pump inhibitors and histamine 2 receptor antagonists, placed patients at a greater risk of suffering severe vitamin B12 deficiency.

The study looked at 25,956 patients diagnosed with vitamin B12 deficiency and compared them to a control group of 184,199 patients without the deficiency. Exposure to the medication for at least two or more years and high doses were directly linked to vitamin B12 deficiency. The occurrence was more common among women and young people than others. Interestingly, the risk came down significantly with a discontinuation of the medication.

The drugs, while preventing production of gastric acid, often ends up with an "malabsorption" of vitamin B12, researchers said, while explaining the occurrence. 

"We cannot completely exclude residual confounding [factors besides the drugs] as an explanation for these findings, but, at minimum, the use of these medications identifies a population at higher risk of B12 deficiency, independent of additional risk factors," the authors concluded. "These findings do not recommend against acid suppression for persons with clear indications for treatment, but clinicians should exercise appropriate vigilance when prescribing these medications and use the lowest possible effective dose. These findings should inform discussions contrasting the known benefits with the possible risks of using these medications."

The study has been reported in JAMA.

The findings bring concern as vitamin B12 deficiency has been associated with brain disorders like dementia, anemia, neurological damage and depression.