Drinking water and dietary sources of nitrate and nitrite and risk of glioma

Objective. Dietary nitrite has been associated with increased glioma risk; however, drinking water nitrate has not been extensively evaluated. Methods. We conducted a population-based case-control study of adult glioma in Nebraska. Water utility nitrate measurements were linked to residential water source histories. We computed average nitrate exposure over a 20-year period. A food frequency questionnaire was used to assess dietary nitrate and nitrite. Results. Increasing quartiles of the average nitrate level in drinking water were not significantly associated with risk (adjusted odd ratios: 1.4, 1.2, 1.3). Risk was similar among those with both higher and lower intakes of vitamin C, an inhibitor of N-nitroso compound formation. Dietary nitrite intake was not associated with risk. Conclusions: Our study does not support a role for drinking water and dietary sources of nitrate and nitrite in risk of adult glioma.