Regular use of an over-the-counter heartburn medication taken by millions of people can speed up the ageing of blood vessels, according to new research.
Heartburn, also known by its medical name of reflux, occurs when stomach acid backs up into the oesophagus, causing irritation and damage.
Most people have experienced mild heartburn after a heavy meal, but severe attacks - known as gastroesophageal reflux disease or GERD - may require sufferers to seek treatment.
A common way many find relief is with medications called proton pump inhibitors (PPIs), which help reduce the buildup of stomach acids.
Recent studies have linked the use of PPIs to several serious illnesses, including heart disease, kidney disease and dementia, and researchers wanted to examine the effects of the medication on blood vessel cells.
Researchers at the Houston Methodist Research Institute (HMRI) in the US found the regular use of PPIs accelerated biological aging in human endothelial cells which line the inside of blood vessels.
Study lead author Professor John Cooke said: "When healthy, human endothelial cells create a Teflon-like coating that prevents blood from sticking.
"When older and diseased, the endothelium becomes more like Velcro, with blood elements sticking to the vessel to form blockages."
The researchers found the pumps also stop the acid production by the lysosomes in the cells lining the blood vessel walls, which help clears waste products from around the cells. This therefore leads to a buildup of waste which causes the cell to age rapidly.
Professor Cooke, of the Department of Cardiovascular Sciences at the HMRI, said: "Lysosomes are like the garbage disposal of cells.
"They need to generate acid to get rid of cellular rubbish, and when cellular rubbish accumulates the cells age faster."
The researchers say PPIs can be effective for short-term use, they are not meant for extended treatment.
They have called for regulators to re-examine the safety of the medication and for doctors to only recommend its use for short-term treatment.
Professor Cooke said: ""With the knowledge that PPIs are being used by millions of people for indications and durations that were never tested or approved, it may be time for the pharmaceutical industry and regulatory agencies to re-visit the specificity and the safety of these agents.
"Unless otherwise indicated, physicians should consider PPIs only for short-term use for relief of symptoms of GERD, since we now have a 'smoking gun' that helps explain the consistent observational evidence of increased risk."
The researchers pointed out that their results, published online by the journal Circulation Research, do have limitations as two different PPIs were tested, only one of which esomeprazole, brand name Nexium, is commercially available in the US.
The study also did not show how PPIs actually impair the lysosome's ability to produce enough acid to clear waste, and as this study was in a laboratory setting, it could not show whether PPIs act in the same way within the human body,
The researchers said long-term clinical trials are necessary to establish the full effects of the medication.