Short-term soy isoflavone intervention in patients with localized prostate cancer: a randomized, double-blind, placebo-controlled trial

PLoS One. 2013 Jul 12;8(7):e68331. doi: 10.1371/journal.pone.0068331. Print 2013.


Purpose: We describe the effects of soy isoflavone consumption on prostate specific antigen (PSA), hormone levels, total cholesterol, and apoptosis in men with localized prostate cancer.

Methodology/principal findings: We conducted a double-blinded, randomized, placebo-controlled trial to examine the effect of soy isoflavone capsules (80 mg/d of total isoflavones, 51 mg/d aglucon units) on serum and tissue biomarkers in patients with localized prostate cancer. Eighty-six men were randomized to treatment with isoflavones (n=42) or placebo (n=44) for up to six weeks prior to scheduled prostatectomy. We performed microarray analysis using a targeted cell cycle regulation and apoptosis gene chip (GEArrayTM). Changes in serum total testosterone, free testosterone, total estrogen, estradiol, PSA, and total cholesterol were analyzed at baseline, mid-point, and at the time of radical prostatectomy. In this preliminary analysis, 12 genes involved in cell cycle control and 9 genes involved in apoptosis were down-regulated in the treatment tumor tissues versus the placebo control. Changes in serum total testosterone, free testosterone, total estrogen, estradiol, PSA, and total cholesterol in the isoflavone-treated group compared to men receiving placebo were not statistically significant.

Conclusions/significance: These data suggest that short-term intake of soy isoflavones did not affect serum hormone levels, total cholesterol, or PSA.

Trial registration: NCT00255125.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / genetics
  • Biomarkers, Tumor / genetics
  • Cell Cycle / genetics
  • Cholesterol / blood
  • Double-Blind Method
  • Estrogens / blood
  • Humans
  • Isoflavones / therapeutic use*
  • Male
  • Middle Aged
  • Phytotherapy
  • Placebos
  • Prostate-Specific Antigen / blood
  • Prostatic Neoplasms / blood
  • Prostatic Neoplasms / drug therapy*
  • Prostatic Neoplasms / genetics
  • Prostatic Neoplasms / pathology*
  • Soybeans / chemistry*
  • Testosterone / blood
  • Time Factors


  • Biomarkers, Tumor
  • Estrogens
  • Isoflavones
  • Placebos
  • Testosterone
  • Cholesterol
  • Prostate-Specific Antigen

Associated data


Grant support

The “Soy Isoflavones in Prostate Cancer Study” was supported by VA Merit Review grants (PV, SB, SKB) and the University of Kansas Cancer Center Pilot Grant program (JHR). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.