Geographic and social class variation within the UK in levels of salivary nitrates and nitrites. A preliminary report

Abstract

In the study, the first results of which are reported here, salivary nitrate and nitrite levels were examined in populations drawn from regions of the UK which differ in mortality rates for gastric cancer. The aims were to see, firstly, whether there was an equivalent geographic variation for nitrate and nitrite levels and, secondly, whether within each region any socio-economic or dietary characteristics correlated with the salivary levels. The results show that the nitrate and nitrite levels are significantly higher in residents from the Oxford region (low gastric cancer incidence area) than in residents from the north-east of England and north Wales (high-incidence areas). Further, within each area there is a noticeable relationship between nitrate and nitrite levels and age and social class. The social class trend is, as with the geographic trend, the inverse of that for stomach cancer risk. It is felt that the explanation of these results is probably a greater consumption of fresh, nitrate-containing vegetables by people in the Oxford region and by those in higher socio-economic groups. The implications that these results have for the nitrate hypothesis in relation to gastric cancer is discussed.