Epidemiology

British Journal of Cancer (2009) 101, 185–191. doi:10.1038/sj.bjc.6605137 www.bjcancer.com
Published online 16 June 2009

Urinary phytoestrogen excretion and prostate cancer risk: a nested case–control study in the Multiethnic Cohort

S-Y Park1, L R Wilkens1, A A Franke2, L Le Marchand1, K K Kakazu2, M T Goodman1, S P Murphy1, B E Henderson3 and L N Kolonel1

  1. 1Epidemiology Program, Cancer Research Center of Hawaii, University of Hawaii, Honolulu, HI 96813, USA
  2. 2Natural Products and Cancer Biology Program, Cancer Research Center of Hawaii, University of Hawaii, Honolulu, HI 96813, USA
  3. 3Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA

Correspondence: Dr S-Y Park, Epidemiology Program, Cancer Research Center of Hawaii, University of Hawaii, 1236 Lauhala Street, Honolulu, HI 96813, USA; E-mail: spark@crch.hawaii.edu

Received 24 March 2009; Revised 20 May 2009; Accepted 20 May 2009; Published online 16 June 2009.

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Abstract

Background:

  

Phytoestrogens are of special interest in prostate cancer research because populations in Asia with a high consumption of phytoestrogens have a lower incidence of the disease than comparable populations in Western countries.

Methods:

  

This case–control study is nested within a large multiethnic cohort in Hawaii and California. Urine samples were analysed for daidzein, genistein, equol, and enterolactone among 249 incident prostate cancer cases and 404 controls matched on age, race/ethnicity, date/time of specimen collection, and fasting status.

Results:

  

The median excretion of daidzein was 0.173 nmol mg-1 creatinine in cases and 0.291 in controls (P=0.01), and the median excretion of genistein was 0.048 in cases and 0.078 in controls (P=0.05). An inverse association was seen for daidzein overall (odds ratio for the highest vs lowest quintile=0.55, 95% confidence interval=0.31–0.98, Ptrend=0.03) and seemed to apply to localized (Ptrend=0.08) as well as advanced or high-grade cancer (Ptrend=0.09). This association was consistent across the four ethnic groups examined. Although the relationship was weaker for genistein, the odds ratios and trends were similarly inverse. Urinary excretion of equol and enterolactone was not significantly related to prostate cancer risk.

Conclusion:

  

Our findings suggest that high intake of isoflavones, as reflected by urinary excretion of daidzein and genistein, may be protective against prostate cancer.

Keywords:

phytoestrogens, urinary excretion, prostate neoplasms, case–control study, multiethnic population