Nitrate intake and the risk of thyroid cancer and thyroid disease

Mary H. Ward, Briseis A. Kilfoy, Peter J. Weyer, Kristin E. Anderson, Aaron R. Folsom, James R. Cerhan

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132 Scopus citations

Abstract

BACKGROUND: Nitrate is a contaminant of drinking water in agricultural areas and is found at high levels in some vegetables. Nitrate competes with uptake of iodide by the thyroid, thus potentially affecting thyroid function. METHODS: We investigated the association of nitrate intake from public water supplies and diet with the risk of thyroid cancer and self-reported hypothyroidism and hyperthyroidism in a cohort of 21,977 older women in Iowa who were enrolled in 1986 and who had used the same water supply for >10 years. We estimated nitrate ingestion from drinking water using a public database of nitrate measurements (1955-1988). Dietary nitrate intake was estimated using a food frequency questionnaire and levels from the published literature. Cancer incidence was determined through 2004. RESULTS: We found an increased risk of thyroid cancer with higher average nitrate levels in public water supplies and with longer consumption of water exceeding 5 mg/L nitrate-N (for ≥ 5 years at >5 mg/L, relative risk [RR] = 2.6 [95% confidence interval (CI) = 1.1-6.2]). We observed no association with prevalence of hypothyroidism or hyperthyroidism. Increasing intake of dietary nitrate was associated with an increased risk of thyroid cancer (highest vs. lowest quartile, RR = 2.9 [1.0-8.1]; P for trend = 0.046) and with the prevalence of hypothyroidism (odds ratio = 1.2 [95% CI = 1.1-1.4]), but not hyperthyroidism. CONCLUSIONS: Nitrate may play a role in the etiology of thyroid cancer and warrants further study.

Original languageEnglish (US)
Pages (from-to)389-395
Number of pages7
JournalEpidemiology
Volume21
Issue number3
DOIs
StatePublished - May 1 2010

ASJC Scopus subject areas

  • Epidemiology

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    Ward, M. H., Kilfoy, B. A., Weyer, P. J., Anderson, K. E., Folsom, A. R., & Cerhan, J. R. (2010). Nitrate intake and the risk of thyroid cancer and thyroid disease. Epidemiology, 21(3), 389-395. https://doi.org/10.1097/EDE.0b013e3181d6201d