Heartburn pills taken by millions of patients increase the risk of heart disease and stomach cancer, scientists claim.
The drugs, known as proton pump inhibitors (PPIs) can also trigger chronic kidney disease.
They have been linked to premature deaths before.
In a report published in the British Medical Journal, scientists say the risk increases with the duration of use even when the medications are taken at low doses.
Senior author Professor Ziyad Al-Aly, of Washington University, St Louis, US, said: “Taking PPIs over many months or years is not safe, and now we have a clearer picture of the health conditions associated with long-term use.”
The medications are available over the counter under brand names including Prilosec, Prevacid and Zegerid.
They bring relief by reducing gastric acid and are among the most commonly used tablets in the UK.
