Long-term use of commonly prescribed heartburn drugs increases the likelihood of being deficient in a vital B vitamin, a study has shown.
Lack of vitamin B12 can increase the risk of dementia, nerve damage, anaemia and other conditions, some of which may be irreversible.
Scientists who studied a large population of US patients found an association between taking some antacid medications and diagnosed vitamin B12 deficiency.
Stomach acids are known to aid vitamin B12 absorption. Suppressing the acids, to combat heartburn and acid reflux, or treat ulcers, may lead to a health-threatening lack of the vitamin in the body, the researchers believe.
The study is the first large population-based investigation linking vitamin B12 deficiency to antacid drugs known as protein pump inhibitors (PPIs), one of the most commonly prescribed medicines.
Examples of PPIs include the drugs esomeprazole, lansoprazole, omeprazole, pantoprazole, and rabeprazole.
Researchers from Kaiser Permanente, a leading US health provider, compared data on almost 26,000 patients diagnosed with vitamin B12 deficiency in northern California and more than 184,000 "control" patients who were not B12 deficient.
"Patients who took PPI medications for more than two years had a 65% increase in their risk of B12 deficiency," said study leader Dr Douglas Corley, a gastroenterologist with the Kaiser Permanente Division of Research. "Higher doses also were associated with an increased risk, compared with lower doses.
"Kaiser Permanente's electronic health records allowed us to look at what happens in the real world for these commonly used medications."
Among the vitamin deficient patients, 12% had used PPIs for at least two years compared with 7.2% of controls.
A related class of antacid drugs called histamine-2-receptor agonists (H2RAs) were also associated with vitamin B12 deficiency, but to a lesser extent.
The findings are reported in the Journal of the American Medical Association.
Dr Corley added: "This research raises the question of whether people who are taking acid-depressing medications long term should be screened for vitamin B12 deficiency. It's a relatively simple blood test, and vitamin supplements are an effective way of managing the vitamin deficiency, if it is found."