Nitrate and nitrite exposure in Italian populations with different gastric cancer rates.

Exposure to nitrate and nitrite from dietary sources was estimated by questionnaire and measurement of salivary levels of the ions in residents of four regions of Italy with longstanding, contrasting, gastric cancer mortality rates. Whether using salivary levels or dietary questionnaire estimations no association was found between nitrate and nitrite exposure and gastric cancer mortality rates. For salivary nitrate and nitrite, the intra-provincial variation was greater than any inter-province difference. However, for dietary nitrate and nitrite intakes, there were significant differences between the regional groups (but not related to gastric cancer risk). Despite the limitations of the methods used, there was a weak positive association between salivary concentrations of nitrate and questionnaire assessment. Dietary factors are likely to play key roles at different stages of the gastric carcinogenic process. Nitrate may play a part but is unlikely to be a rate-limiting factor in all individuals or populations.