Drugs used to treat indigestion and heartburn can increase the risk of the 'brittle bone' disease osteoporosis, warn researchers.
A Canadian study has revealed those who use them regularly for five years had a 44 per cent higher chance of hip fracture.
The drugs are called proton pump inhibitors, or PPIs, and are available both on prescription and over the counter in low doses.
Patients with gastro-oesophageal reflux disorder, a more serious condition involving chronic heartburn, have to take them daily for up to two months. But many end up staying on the drugs permanently to keep heartburn symptoms at bay.
To reach the conclusion, the research team at the University of Manitoba in Canada studied more than 60,000 adults aged over 50, including nearly 16,000 who had suffered a fractured hip, spine or wrist due to osteoporosis.
When they analysed prescription records, they found those with hip fractures were 62 per cent more likely to have used PPIs for five years or more than those with healthy hips.
Among those on the drugs for seven years or more, the risk of a fracture soared by more than 400 per cent.
The study has been published in the Canadian Medical Association Journal.
It's not clear how the drugs might damage bones. One theory is that by blocking acid production, they stop the body from absorbing calcium needed to build strong bones.
The researchers said for patients with severe stomach problems, such as bleeding ulcers, the benefits of the drugs will still outweigh the risks.
But those using the drugs routinely to control mild indigestion should seek medical advice.
"These are very safe drugs but there are some areas where they are probably overused, such as for minor indigestion," The Daily Mail quoted Professor Chris Hawkey, president-elect of the British Society of Gastroenterology, as saying.