title: Is daidzein non-metabolizer a high risk for prostate cancer? A case-controlled study of serum soybean isoflavone concentration.
abstract: BACKGROUND
  It has been postulated that soybean isoflavones act as inhibitory factors in prostate cancer. However, to date there have been no case-controlled clinical studies carried out to compare the circulating concentrations of isoflavones in prostate cancer patients and control subjects.
  
  
  METHODS
  The serum levels of genistein, daidzein and equol were determined and compared in 253 experimental subjects (141 prostate cancer patients and 112 cancer-free controls).
  
  
  RESULTS
  The serum concentrations of isoflavones were compared in hospitalized and non-hospitalized subjects and for both the prostate cancer patients and the controls the concentrations were lower in the hospitalized subjects. The serum concentrations of genistein and daidzein were compared in subjects <70 years of age and subjects >/=70 years old and the levels were significantly lower in the younger group. Contrary to our expectation, comparison of the patient group and the control group revealed the serum concentrations of isoflavones to be higher in the patient group. Daidzein non-metabolizers were compared in the hospitalized experimental subjects of the patient group and the control group and they were significantly more common in the patient group. The poorly differentiated cancer patient group included a significantly lower percentage of daidzein metabolizers.
  
  
  CONCLUSIONS
  The above findings revealed that equol itself or some unknown factor regulating the metabolism of daidzein is deeply involved in the biology of prostate cancer. Future studies are urgently needed to compare the incidence of daidzein metabolizers among various countries.
authors.affiliation: Department of Urology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan. akazah@md.tsukuba.ac.jp
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Akaza
authors.forename: Naoto
authors.initials: N
authors.lastname: Miyanaga
authors.forename: Naomi
authors.initials: N
authors.lastname: Takashima
authors.forename: Seiji
authors.initials: S
authors.lastname: Naito
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Hirao
authors.forename: Taiji
authors.initials: T
authors.lastname: Tsukamoto
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Mori
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D019833:Genistein / Q000097:blood; D006801:Humans; D007529:Isoflavones / Q000097:blood* / Q000378:metabolism; D008297:Male; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis; D012306:Risk; D013025:Glycine max / Q000737:chemistry*
chemical_list: D007529:Isoflavones; C004742:daidzein; D019833:Genistein; D017430:Prostate-Specific Antigen