PPI are the most commonly used treatment for chronic acid reflux, or 'heartburn', a painful burning sensation in the chest, neck and throat which is experienced by almost a third of people in developed countries.
Regular and prolonged heartburn is known to cause 'benign oesophagitis', a reversible inflammation of the gullet.
However if left untreated a condition called Barrett's Oesophagus (BE) occurs in around 10 per cent of sufferers, which can in turn develop into a potentially fatal cancer called oesophageal adenocarcinoma.
While PPIs had an excellent safety record, it was unclear if long-term use of these drugs to reduce the discomfort of heartburn could increase the risk of developing either BE or the spread of the associated cancer.
But, the new research carried out at Queen Mary, University of London and Leicester Royal Infirmary, has given the most conclusive evidence yet that this is not the case.
Professor Janusz Jankowski, who co-authored the study, said: "This is one of the most detailed studies investigating both the laboratory and clinical side of proton pump inhibitor drugs. As a consequence we are now better able to inform patients of the good benefit/risk ratio of this commonly prescribed therapy."
Tests carried out during the two-year study looked at tissue sampled from the oesophagus lining of ninety volunteers, each of whom were given PPI drugs at either a high or low dosage.
Researchers found that there was no difference in the rate at which BE developed, neither was there a change in the number of precancerous cells in either group.
Despite fears about how the treatments might affect people already suffering from BE, the study showed that there was no evidence that this led to any worsening of the condition or any extra incidences of cancer.
PPIs work by blocking the action of gastrin, a hormone that controls acid levels in the stomach, and is known to increase the normal movement of cells in the gastro-intestinal tract.
Since PPI therapy increases the levels of gastrin in the body, it had been thought this could cause expansion of BE affected tissue, but this was not found to be the case.
In fact, the scientists observed neither expansion nor contraction of the abnormal tissue.
The study has been published in the peer reviewed journal Gut.