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Holiday revellers beware: Seasonal indulgences like eggnog and fruitcake might give you heartburn, but the acid-fighting medicine you take for relief might lead to something worse, researchers believe.

People on popular prescription heartburn drugs such as Nexium seem more prone to getting a potentially dangerous diarrhea caused by the bacterium Clostridium difficile, researchers at Montreal's McGill University have shown.

C. difficile, as it's more commonly known, can cause severe diarrhea and crampy intestinal inflammation called colitis. Severe cases can lead to or contribute to death.

Dr. Sandra Dial and colleagues at McGill examined data on more than 18,000 patients in the United Kingdom from 1994 to 2004. During that time, 1,672 cases of C. difficile were diagnosed, and the numbers increased from less than one per 100,000 in 1994 to 22 per 100,000 last year.

Patients with prescriptions for powerful antacid drugs called proton pump inhibitors were almost three times more likely to be diagnosed with the bug than those not taking the drugs. Those on less potent prescription drugs called H2 receptor antagonists, which include Pepcid and Zantac, were two times more likely than non-users to get C. difficile infections.

The widely used and heavily promoted drugs reduce levels of gastric acid that can keep C. difficile infection from developing.

Dr. Clifford McDonald, a leading C. difficile researcher who was not involved in Dr. Dial's study, said proton pump inhibitors recently were implicated in a C. difficile outbreak at a hospital and nursing homes in Maine.

“It's not surprising in my mind that there could be some association,” said Dr. McDonald, a physician epidemiologist at the U.S. Centers for Disease Control in Atlanta.

Dr. McDonald stressed it would be important to determine if there is a link, “because, boy, everyone and their brother seems to be on them.”

Most study patients hadn't been recently hospitalized and weren't taking antibiotics, both risk factors for developing C. difficile infections.

Also, most patients hadn't been diagnosed with ulcers or acid reflux, so it's possible many simply had heartburn, Dr. Dial said.

“Heartburn in and of itself isn't dangerous,” and can often be treated with less potent drugs, Dr. Dial said.

Her study appears in Wednesday's Journal of the American Medical Association.

A co-author is a consultant for AstraZeneca Inc., which markets Nexium, and Altana Pharma, which makes and markets another prescription heartburn drug, Protonix, in Europe. A spokesman for Wyeth, which markets Protonix in the United States, said the company hadn't seen the research and declined comment.

AstraZeneca spokeswoman Cindy Callaghan said patient safety is the company's top priority and that the findings are not the final word.

“Further research is needed in this particular area to determine the validity of a potential link,” she said.

C. difficile associated diarrhea historically has occurred mainly in patients on antibiotics or with underlying illnesses, especially those in hospitals or nursing homes. But infections increasingly have been reported in the community.

Doctors think the growing trend is due in part to overuse of antibiotics but the new data suggest overuse of acid-fighting drugs may be another reason, said Dr. Michael Brown, a gastroenterologist at Rush University Medical Center in Chicago, who was not involved in the study.

The drugs are popular because they are so effective at fighting stomach acid, and are generally very safe, Brown said.

Dr. Brown said short-term use of potent acid-fighting drugs for occasional over-imbibing is unlikely to increase infection risks in otherwise healthy people, but that the results suggest doctors and patients “have to think twice about using such heavy acid suppression” over the long term.