Humans are exposed to inorganic nitrate from two main sources – nitric oxide oxidation and dietary intake. Nitric oxide is continuously generated in several tissues in the body to regulate blood flow and provide host-defense against pathogens. Shortly after synthesis it is oxidised to form inorganic nitrate; we are exposed to about 1millimole each day from this source. Additionally we eat in our diet an average of 1-3 millimoles of nitrate, mainly from green vegetables which have a high concentration of this ion. Nitrate is metabolised in the body in an unusual way. Salivary glands concentrate it from the blood and secrete it into saliva. On the surface of the tongue it is reduced to nitrite by specialised bacteria which elaborate a nitrate reductase enzyme. Nitrite is swallowed and acidification in the stomach causes the generation of large amounts of nitric oxide gas. We have shown that this process of enterosalivary circulation of nitrate is capable of killing a large number of potentially harmful bacteria and other pathogens in the stomach, which may otherwise cause gastroenteritis. There is also increasing evidence that nitric oxide formed in the stomach from this process will help prevent ulcers and also prevent blood clots which cause heart disease. We have shown that a similar process happens on the skin surface where nitrate is reduced to nitrite by commensal bacteria and skin acidity generates nitric oxide which also is likely to be important in protecting us from infection. We have shown that application of acidified nitrite to the skin will effectively treat a range of bacterial and fungal infections. These studies have led us to believe that nitrate is an important beneficial component of our diet and that current legislation to limit nitrate content of foods and water should be revised in view of these findings.