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.