In the NHANES surveys of the years 2001–2002 and
2003–2004, PSA serum and phytoestrogen urine levels were
measured (20). To address our study questions, our study sample
included men meeting the following criteria: age 40 yr or
older, measured blood concentration of PSA, measured urine
concentration of phytoestrogens, never diagnosed with prostate
cancer, no recent prostate biopsy, prostate examination or infection
prior to venipuncture. The 2001–2002 and 2003–2004
NHANES surveys included 10,301 males, of which 3326 were
age 40 years or older. PSA has been measured in 2701 men;
155 of them did not meet the prostate exclusion criteria. So,
after subtracting those who had no phytoestrogen measurement
(N = 2546 as phytoestrogens were measured only in a random
subsample of the NHANES populations), 824 men were eligible
for our study.