Proton pump inhibitors (PPIs) — a widely prescribed group of medications that combat heartburn, GERD (gastroesophageal reflux disease), and ulcers — are the most widely prescribed class of drugs worldwide, with annual global sales of about $13 billion. More than 15 million Americans take the drugs, both prescription-strength and the commonly available over-the-counter versions.

These drugs might ease digestive discomfort and stave off gastroesophageal problems, but they might also be extremely hazardous to your health — even though they’re not generally considered to be among the 25 most dangerous drugs.

A new study conducted by researchers at Washington University School of Medicine in St. Louis and the city’s Veterans Affairs Health Care System, following up on research they conducted in 2017, suggests that such commonly used drugs as Nexium, Prilosec, Prevacid, and Protonix put those who take them at risk for premature death from kidney and heart disease and stomach cancer. They have also been linked to digestive hormone imbalances and increased risks for pneumonia, dementia, and bone fractures.

While the results indicate a difference in mortality of only 45 people per 1,000, the study’s principal author, Ziyad Al-Aly, an assistant professor of medicine at the university, noted that “Given the millions of people who take PPIs regularly, this translates into thousands of excess deaths every year.”

The most alarming thing, Al-Aly added, was that more than half the people taking PPIs didn’t really need them. The study also found that more than 80% of the subjects were using low doses of prescription PPIs or over-the-counter versions. He recommended that over-the-counter PPIs should carry clear warnings about their potential health risks, and that in most cases, people shouldn’t take them for more than 14 days consecutively. More studies may have to be conducted to determine the potential danger PPIs cause and if even some of them will need to be recalled. For reference, these are the 18 of the worst drug recalls in history.