title: Prediagnostic toenail cadmium and zinc and subsequent prostate cancer risk.
abstract: BACKGROUND
  Cadmium is a recognized human lung carcinogen that has also been positively associated with prostate cancer mainly in occupationally exposed men. The association between dietary and supplemental zinc intake and prostate cancer has not been consistent in epidemiologic studies. We evaluated the association between prediagnostic toenail cadmium and zinc concentrations and risk of prostate cancer in a cohort in which the primary route of exposure to cadmium and zinc is the diet.
  
  
  METHODS
  Included in the analysis were 115 prostate cancer cases and 227 age-matched controls nested in the prospective CLUE II study located in Washington County, MD. Participants provided toenail samples at baseline in 1989. Furnace atomic absorption and flame atomic absorption were used to determine toenail cadmium and zinc concentrations, respectively. Odds ratios (OR) and 95% confidence intervals (CI) were estimated from conditional logistic regression models.
  
  
  RESULTS
  Median toenail cadmium and zinc concentrations did not statistically significantly differ between prostate cancer cases (cadmium, 45.9 ppb; zinc, 155.3 ppm) and controls (cadmium, 54.5 ppb; zinc, 164.0 ppm). Prostate cancer risk did not increase with increasing concentrations of cadmium (P trend = 0.9) and did not decrease with increasing concentrations of zinc (P trend = 0.2). For both metals, the ORs for the top four fifths were each below 1.0 when compared with the bottom fifth.
  
  
  CONCLUSIONS
  Men who have high toenail cadmium concentrations in the range observed in this general population sample were not at an increased risk for prostate cancer. Although there was no evidence of a linear dose-response, these findings suggest that risk of prostate cancer may be slightly lower among men with moderate and higher zinc intake.
authors.affiliation: Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205, USA. eplatz@jhsph.edu
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Platz
authors.forename: Kathy J
authors.initials: KJ
authors.lastname: Helzlsouer
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Hoffman
authors.forename: J Steven
authors.initials: JS
authors.lastname: Morris
authors.forename: Connie K
authors.initials: CK
authors.lastname: Baskett
authors.forename: George W
authors.initials: GW
authors.lastname: Comstock
mesh_terms: D000368:Aged; D002104:Cadmium / Q000009:adverse effects* / Q000032:analysis; D015331:Cohort Studies; D004032:Diet; D004781:Environmental Exposure; D006801:Humans; D008297:Male; D008875:Middle Aged; D009262:Nails / Q000737:chemistry; D011237:Predictive Value of Tests; D018570:Risk Assessment; D014034:Toes; D015032:Zinc / Q000032:analysis / Q000494:pharmacology*
chemical_list: D002104:Cadmium; D015032:Zinc