Gastric juice – a natural‐born killer

Abstract

Sirs, Acidic gastric juice is found in all vertebrates, and its main function is to inactivate micro-organisms. The preservation of this energy-consuming and hazardous function (acid-related diseases) reflects its biological importance. Gastric juice is a unique combination of hydrochloric acid, lipase and pepsin. In a recent review, Williams and McColl focused only on gastrointestinal bacterial overgrowth induced by proton pump inhibitors.1 We missed a discussion concerning other infective agents.2 Most viruses, except enteroviruses, are destroyed by gastric juice. Surprisingly, studies on decreased gastric acidity and susceptibility to viral infections are almost non-existing. Prion diseases have recently attracted much attention because of the link between bovine spongiform encephalopathy in cattle and the new variant Creutzfeldt–Jakob disease in humans.3, 4 Transmission from cattle to humans is by contaminated food.4 The recent demonstration of infectious prions in skeletal muscle of deer with chronic-wasting disease, a prion disease of American cervids, is also of concern.5 The gastric juice may be the only level of defence against prion infection as these agents do not activate the immune system.6 Prions are relatively resistant against inactivation.7 However, the combination of low pH and proteolytic activity in gastric juice on prion infectivity has not been studied. In 2002, we demonstrated that a slight decrease in gastric acidity by ranitidine increased susceptibility of mice to a strain of scrapie agent.8 Moreover, infections may be responsible for more than 15% of all malignancies.9 These effects are hard to reveal in drug safety studies because carcinogenesis may be a slow process developing over decades. When discussing infections as a consequence of proton pump inhibitors, it seems insufficient to focus only on bacterial overgrowth.1 Therefore, we find it premature to conclude that proton pump inhibitors have an excellent safety profile.10