The human stomach normally contains high levels of bioactive nitric oxide. This NO derives from salivary nitrate that is converted to nitrite by oral bacteria and thereafter non-enzymatically reduced in the acidic gastric lumen to NO. Nitrate is a common component in vegetables, and after ingestion it is absorbed in the small intestine. Interestingly, circulating nitrate is then concentrated by the salivary glands. Hence, intake of nitrate-rich vegetables results in high levels of NO in the stomach. The physiological effect of the high concentration of NO gas normally present in the gastric lumen has been hitherto unknown and has therefore been the focus of my research. We have shown that NO produced in the gastric lumen after nitrate ingestion increases gastric mucosal blood flow and the thickness of the firmly adherent mucus layer in the stomach. The blood flow and mucus layer are essential defense mechanisms that protect the mucosa from luminal acid and noxious agents. We have demonstrated that a nitrate-rich diet protects against Nonsteroidal anti-inflammatory drugs-induced gastric damage, as a result of the increased formation of NO in the stomach. We have also shown that the gastroprotective effect attributed to nitrate depends completely on conversion of nitrate to nitrite by the bacterial flora, colonizing the tongue, and that the oral microflora therefore is important in regulating physiological conditions in the stomach. This research challenges the current dogma that nitrate intake is hazardous, and on the contrary suggests that dietary nitrate plays a direct role in regulating gastric homeostasis. It is likely that a sufficient supply of nitrate in the diet together with the oral microflora is important for preventing pathological conditions in the gastrointestinal tract.