Japanese traditional diet contains considerably more nitrate/nitrite than the European foods. 80% of dietary nitrate originates from vegetables. Green leafy vegetables, especially spinach, salad and seaweed are rich in nitrates. Other vegetables contain nitrate at lower concentrations, but because they are consumed in greater quantity, they may contribute more nitrate and thus nitrite from the diet. Nitrate/nitrite is attributed multiple health benefits. Japanese people have an exceptional longevity and the lowest rate of heart diseases. On the other hand, gastric cancer rate is high too. Nitrate/nitrite is strongly correlated with these phenomena. Is this high nitrate consumption protective or damaging? Understanding dietary nitrite and nitrate consumption and its metabolism therefore becomes very important.