title: Plasma levels of nitrate and risk of prostate cancer: a prospective study.
abstract: BACKGROUND
  Nitrate and nitrite supplements have recently been shown to improve cardiovascular health, but there is concern that these supplements could contribute to the development of cancer. Previous small, cross-sectional studies reported positive associations between circulating nitrate/nitrite levels and cancer. Prospective studies examining the association between plasma nitrate and cancer, especially prostate cancer, are lacking.
  
  
  METHODS
  We conducted a nested case-control study within the Health Professionals Follow-up Study. Baseline blood samples were collected in 1994, and incident cases of prostate cancer were identified from 1997 to 2005. Baseline plasma levels of nitrate were measured in the 630 cases and 630 matched controls.
  
  
  RESULTS
  We have found that baseline levels of plasma nitrate were not associated with risk of prostate cancer. Compared to quintile 1, the relative risk from quintiles 2 to 5 were 1.13 [95% confidence interval (CI), 0.78-1.63], 0.93 (95% CI, 0.63-1.38), 0.95 (95% CI, 0.65-1.39), and 0.99 (95% CI, 0.68-1.48); Ptrend was 0.9 after adjustment of multivariate risk factors. When analyses were restricted to men fasting more than 6 hours, the trend was similar. Furthermore, plasma nitrate seemed to be inversely associated with advanced-stage prostate cancer. The relative risk across extreme quartiles was 0.44 (95% CI, 0.17-1.12; Ptrend = 0.07) for the whole dataset and 0.30 (95% CI, 0.09-0.99; Ptrend = 0.05) for the fasting dataset.
  
  
  CONCLUSIONS
  In summary, we did not find an increased risk of prostate cancer associated with higher plasma nitrate levels. A potential protective association between nitrate and aggressive forms of prostate cancer requires confirmation.
  
  
  CONCLUSIONS
  Nitrate-nitrite-nitric oxide pathway has emerged as a new therapeutic pathway for chronic diseases. The results of this study certainly merit replications in other prospective studies.
authors.affiliation: Division of Epidemiology and Biostatistics, Department of Environmental Health, University of Cincinnati Medical Center, Cincinnati, OH 45267, USA. tianying.wu@uc.edu
authors.forename: Tianying
authors.initials: T
authors.lastname: Wu
authors.forename: Yushan
authors.initials: Y
authors.lastname: Wang
authors.forename: Shuk-Mei
authors.initials: SM
authors.lastname: Ho
authors.forename: Edward
authors.initials: E
authors.lastname: Giovannucci
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D015331:Cohort Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009566:Nitrates / Q000097:blood*; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000097:blood* / Q000453:epidemiology / Q000473:pathology; D012307:Risk Factors
chemical_list: D009566:Nitrates