In the present study the amount of nitrate naturally provided by the Japanese diet exceeded the ADI by four times and could therefore be questioned. Although seemingly high, these levels were easy to reach when the participants ate vegetables that corresponded to a typical traditional Japanese diet. Green leafy vegetables present in Japanese food (chingensai, komatsuna and garland chrisantemum etc.) contain on average a similar amount of nitrate as European spinach, and Japanese are high consumers of a variety of mushrooms and seaweed, also rich in nitrate/nitrite (Table 1). The variety and amounts of nitrate rich vegetables eaten every day in the traditional Japanese diet is much greater than in a European diet: almost all the foods shown in Table 1 were included in the daily diet, which corresponded an ordinary Japanese diet. Altogether, these eating habits explain the high daily intake of nitrate. Nitrate intake from dietary sources in our study is similar with the recent report from Bryan’s group, who has calculated that the DASH diet could result in the consumption of up to 1222 mg nitrate per day thereby exceeding by 550% the WHO’s ADI for nitrate in adults [34]. The concentration of nitrate in a single vegetable species varies depending on the soil and growth as well as storage and transport conditions [35]. In our study, we handled the possible variation in concentrations by providing the participants with the foods from the same store.