Each participant was asked to recall and fill in all food and drink items consumed daily during the study periods of 10 days, including detailed information about recipe ingredients. Daily nitrate/nitrite intake calculations were based on the dietary recall, body weight information and referred nitrate/nitrite concentrations of ingested foods [29]. Nitrate contents in various vegetables and Japanese foods (examples are shown in Table 1) were based on the calculations by Tsuji et al. (assessed by ion exchange HPLC–UV chromatography) [29]. Blood pressure was measured manually in a sitting position by the blinded physician according to a standard protocol. There was no wash-out period between the study periods. Measurements were taken before breakfast three times: at baseline, at the shift of diets in the middle and at the end of the study. Blood samples (3 mL) were collected and treated for plasma nitrate and nitrite measurement according to procedure previously described in detail [31]. Blood samples were centrifuged immediately at 2200g for 10 min at 4 °C and the plasma stored at −80 °C until measurement of nitrite and nitrate concentration. Saliva samples were collected at the same time in tubes containing EDTA (final concentration 2 mM) and stored at −80 °C for later nitrate and nitrite determination