To establish a concrete procedure to achieve a steady state plasma NOx concentration with Japanese daily food, NOx contents of about 200 types of food and beverages consumed daily were measured and NOx concentration in plasma was monitored till steady state after various degree of intake of NOx restricted food. The NOx content was found to be high in dark green leaved vegetables and low in grains, processed food, fresh and processed seafood. Tap water and mineral water were found to contain various amounts of NOx that were drastically reduced by treatment with a reverse osmosis column and remained in trace amounts after ion exchange column treatment. NOx content was low in drinks such as cola, but was extremely high in vegetable juice containing dark green leaved vegetables. The intake of high NOx drinks resulted in elevated plasma NOx concentration, but intake of low NOx drinks did not change the plasma NOx concentration. Based on these findings, a steady state could be achieved by 18 hours fasting after the intake of a moderately NOx-restricted diet (about 370 μmoles/day) and by 13 hours fasting after the intake of an extremely NOx-restricted diet (<100 μmoles/day). NOx concentrations in randomly collected blood samples without these conditions were sometimes ten times higher than that at steady state. This procedure can be undertaken under normal Japanese daily life and is expected to be applicable even to outpatients.