Influence of Isoflavone Intake and Equol-producing Intestinal Flora on Prostate Cancer Risk

Background: The age-adjusted incidence rate of prostate cancer (PCa) has been reported to be lower amongAsians than Western populations. A traditional Japanese meal, high in soybean products or isoflavones, maybe 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. Materials and
Methods: We reviewed not onlyrecent epidemiological studies on association of isoflavones with PCa risk, but also recent research on humanintestinal bacteria responsible for converting daidzein into equol. Studies were systematically searched from thedatabase published within the last 5 years of from 2008-2012.
Results: Five out of 6 articles showed significantassociation of isoflavones with a decreased risk of PCa, and two of them consistently showed that equol-producerscarry a significantly reduced risk of PCa. Furthermore, 5 human intestinal bacteria that can convert daidzeininto equol were identified in the last 5 years.
Conclusions: If equol can reduce risk of PCa, a possible strategyfor reducing the risk of PCa may be to increase the proportion of equol-producers by changing the intestinalflora to carrying an equol-producing bacterium with dietary alteration or probiotic technology.