title: Influence of isoflavone intake and equol-producing intestinal flora on prostate cancer risk.
abstract: BACKGROUND
  The age-adjusted incidence rate of prostate cancer (PCa) has been reported to be lower among Asians than Western populations. A traditional Japanese meal, high in soybean products or isoflavones, may be associated with a decreased risk of PCa. Equol, which is converted from daidzein by human intestinal flora, is biologically more active than any other isoflavone aglycone.
  
  
  METHODS
  We reviewed not only recent epidemiological studies on association of isoflavones with PCa risk, but also recent research on human intestinal bacteria responsible for converting daidzein into equol. Studies were systematically searched from the database published within the last 5 years of from 2008-2012.
  
  
  RESULTS
  Five out of 6 articles showed significant association of isoflavones with a decreased risk of PCa, and two of them consistently showed that equol-producers carry a significantly reduced risk of PCa. Furthermore, 5 human intestinal bacteria that can convert daidzein into equol were identified in the last 5 years.
  
  
  CONCLUSIONS
  If equol can reduce risk of PCa, a possible strategy for reducing the risk of PCa may be to increase the proportion of equol-producers by changing the intestinal flora to carrying an equol-producing bacterium with dietary alteration or probiotic technology.
authors.affiliation: Department of Public Health, Sapporo Medical University School of Medicine, Tokyo University, Tokyo, Japan. ysugi@sapmed.ac.jp
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Sugiyama
authors.forename: Naoya
authors.initials: N
authors.lastname: Masumori
authors.forename: Fumimasa
authors.initials: F
authors.lastname: Fukuta
authors.forename: Akihiro
authors.initials: A
authors.lastname: Yoneta
authors.forename: Tokimasa
authors.initials: T
authors.lastname: Hida
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Yamashita
authors.forename: Machiko
authors.initials: M
authors.lastname: Minatoya
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Nagata
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Mori
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Tsuji
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Akaza
authors.forename: Taiji
authors.initials: T
authors.lastname: Tsukamoto
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D060754:Equol / Q000378:metabolism*; D005243:Feces / Q000382:microbiology; D005502:Food; D041981:Gastrointestinal Tract / Q000382:microbiology*; D006801:Humans; D007529:Isoflavones / Q000378:metabolism*; D008297:Male; D055442:Metabolome; D011471:Prostatic Neoplasms / Q000453:epidemiology*
chemical_list: D007529:Isoflavones; D060754:Equol; C004742:daidzein