Dr. Douglas Corley, a Kaiser Permanente gastroenterologist and senior researcher, said a study found participants who took proton pump inhibitors -- sold under brand names such as Prilosec, Prevacid and Nexium -- for more than two years had a 65 percent increased risk of B-12 deficiency.
He said a lack of vitamin B-12 can increase the risk of dementia, nerve damage, anemia and other potentially serious medical problems.
Unlike chewable antacids, which neutralize stomach acid after it has already formed, proton pump inhibitors go after the source by shutting down the cells in the stomach responsible for producing acid.
"But the same cell that makes stomach acid also makes a little protein that helps vitamin B-12 be absorbed," Corley told the San Francisco Chronicle.
Proton pump inhibitors -- mainly used to treat heartburn, stomach acid reflux disease and gastric ulcers -- account for more than 100 million prescriptions a year and about $14 billion in sales, the Chronicle reported.
Many are available by prescription, but some of these drugs -- including Prilosec and Prevacid -- are sold over-the-counter at lower doses. They are typically recommended for short-term use -- up to eight weeks -- but some people take the drugs for years, Corley said.
"It's not that people should stop the medication," Corley told the Chronicle. "It raises the question of whether they should check with their physician to be screened for this vitamin deficiency."