Nitrate and nitrite ingestion and risk of ovarian cancer among postmenopausal women in Iowa. Issue 1 (8th December 2014)

• Record Type: Journal Article
• Authors: Inoue‐Choi, Maki; Jones, Rena R.; Anderson, Kristin E.; Cantor, Kenneth P.; Cerhan, James R.; Krasner, Stuart; Robien, Kim; Weyer, Peter J.; Ward, Mary H.
• Is Part Of: International journal of cancer. Volume 137:Issue 1(2015:Jul. 01)
• Page Start: 173
• Page End: 182
• Publication Date: 2014-12-08
• Subjects: nitrate -- nitrite -- ovarian cancer -- diet -- drinking water -- disinfection byproducts; Cancer -- Periodicals; Cancer -- Prevention -- Periodicals; 616.994
• DOI: 10.1002/ijc.29365
• Languages: English
• ISSNs: 0020-7136

Abstract

Abstract : Nitrate and nitrite are precursors in the endogenous formation of N ‐nitroso compounds (NOC), potential human carcinogens. We evaluated the association of nitrate and nitrite ingestion with postmenopausal ovarian cancer risk in the Iowa Women's Health Study. Among 28, 555 postmenopausal women, we identified 315 incident epithelial ovarian cancers from 1986 to 2010. Dietary nitrate and nitrite intakes were assessed at baseline using food frequency questionnaire data. Drinking water source at home was obtained in a 1989 follow‐up survey. Nitrate‐nitrogen (NO3 ‐N) and total trihalomethane (TTHM) levels for Iowa public water utilities were linked to residences and average levels were computed based on each woman's duration at the residence. We computed multivariable‐adjusted hazard ratios (HR) and 95% confidence intervals (CI) using Cox proportional hazards regression. We tested interactions of nitrate with TTHMs and dietary factors known to influence NOC formation. Ovarian cancer risk was 2.03 times higher (CI = 1.22–3.38, p trend = 0.003) in the highest quartile (≥2.98 mg/L) compared with the lowest quartile (≤0.47 mg/L; reference) of NO3 ‐N in public water, regardless of TTHM levels. Risk among private well users was also elevated (HR = 1.53, CI = 0.93–2.54) compared with the same reference group. Associations were stronger when vitamin C intake was interaction = 0.01 and 0.33 for private well and public supplies, respectively). Dietary nitrate was inversely associated with ovarian cancer risk ( p trend = 0.02); whereas, dietary nitrite from processed meats was positively associated with the risk ( p trend = 0.04). Our findings indicate that high nitrate levels in public drinking water and private well use may increase ovarian cancer risk among postmenopausal women. Abstract : What's new? While environmental factors such as diet are thought to have a role in ovarian cancer, few such factors have been identified. In the present study, the ingestion of nitrate and nitrite was investigated for possible involvement in ovarian cancer. Among postmenopausal women, risk of ovarian cancer was found to be positively associated with elevated nitrate levels in public drinking water supplies and with nitrite intake from processed meats. Elevated nitrate levels in private well water was linked to increased ovarian cancer risk among women with reduced vitamin C intake.