Thyroid cancer risk and dietary nitrate and nitrite intake in the Shanghai women's health study

Authors

  • Briseis Aschebrook-Kilfoy,

    1. Department of Health Studies, The University of Chicago, Chicago, IL
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  • Xiao-Ou Shu,

    1. Department of Medicine, Center for Health Services Research, Vanderbilt University, Nashville, TN
    2. Department of Medicine, Vanderbilt Epidemiology Center and Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TN
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  • Yu-Tang Gao,

    1. Department of Epidemiology, Shanghai Cancer Institute, Shanghai, People's Republic of China
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  • Bu-Tian Ji,

    1. Department of Health Studies, The University of Chicago, Chicago, IL
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  • Gong Yang,

    1. Department of Medicine, Center for Health Services Research, Vanderbilt University, Nashville, TN
    2. Department of Medicine, Vanderbilt Epidemiology Center and Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TN
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  • Hong Lan Li,

    1. Department of Epidemiology, Shanghai Cancer Institute, Shanghai, People's Republic of China
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  • Nathaniel Rothman,

    1. Department of Health Studies, The University of Chicago, Chicago, IL
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  • Wong-Ho Chow,

    1. Department of Health Studies, The University of Chicago, Chicago, IL
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  • Wei Zheng,

    1. Department of Medicine, Center for Health Services Research, Vanderbilt University, Nashville, TN
    2. Department of Medicine, Vanderbilt Epidemiology Center and Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TN
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  • Mary H. Ward

    Corresponding author
    1. Department of Health Studies, The University of Chicago, Chicago, IL
    • Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH/DHHS, 6120 Executive Blvd, EPS 8006, Bethesda, MD 20892, USA
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    • Tel.: +301-435-4713


Abstract

Nitrate and nitrite are precursors in the endogenous formation of N-nitroso compounds and nitrate can disrupt thyroid homeostasis by inhibiting iodide uptake. We evaluated nitrate and nitrite intake and risk of thyroid cancer in the Shanghai Women's Health Study that included 73,317 women, aged 40–70 years enrolled in 1996–2000. Dietary intake was assessed at baseline using a food frequency questionnaire. During approximately 11 years of follow-up, 164 incident thyroid cancer cases with complete dietary information were identified. We used Cox proportional hazards regression to estimate relative risks (RRs). We determined the nitrate and nitrite contents of foods using values from the published literature and focusing on regional values for Chinese foods. Nitrate intake was not associated with thyroid cancer risk [RRQ4 = 0.93; 95% confidence interval (CI): 0.42–2.07; p for trend = 0.40]. Compared to the lowest quartile, women with the highest dietary nitrite intake had about a twofold risk of thyroid cancer (RRQ4 = 2.05; 95%CI: 1.20–3.51), but there was not a monotonic trend with increasing intake (p for trend = 0.36). The trend with increasing nitrite intake from animal sources was significant (p for trend = 0.02) and was stronger for nitrite from processed meats (RRQ4 = 1.96; 95%CI: 1.28–2.99; p for trend < 0.01). Although we did not observe an association for nitrate as hypothesized, our results suggest that women consuming higher levels of nitrite from animal sources, particularly from processed meat, may have an increased risk of thyroid cancer.

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