However, taking endogenous formation of nitrate into account,
this means additional 70 mg of nitrate for an average 70 kg adult
(Gangolli et al., 1994). Furthermore, it was estimated approximately
25% of dietary nitrate is converted to nitrite by bacteria
and nitrate reductase in the oral cavity (Gangolli et al., 1994). Thus
assuming two servings (150 g) of vegetables comes from green leafy
vegetables, again taking the analytical data from this study (Table
1), this means approximately 727.5 mg of nitrate from English
spinach (Fig. 1) is ingested, of which 181.9 mg of nitrite can participate
in nitrosation in the stomach. Based on the above assumptions,
the total nitrite and nitrate burden for an Australian adult
of 70 kg body weight, the intakes per day is approximately 184.4
and 617.7 mg, respectively, sourced from cured meat, spinach
and endogenous nitrate formation. This exceeds the ADI of
4.2 mg for nitrite by 44 times per 70 kg adult per day, and by 2.4
times of ADI of 259 mg nitrate per 70 kg adult per day. However,
it must be noted that the above prediction assumed that nitrite
only came from one serving (50 g) each of bacon and ham
(Fig. 2), and that nitrate intake only came from two servings of
English spinach. Since English spinach had the highest nitrate content,
this predicts the upper extreme of dietary nitrate intake. Furthermore,
the ADI do not include the 25% conversion of dietary
nitrate to nitrite in the oral cavity, which underestimate the total
ingested dietary nitrite.