Effects of a high dose, aglycone-rich soy extract on prostate-specific antigen and serum isoflavone concentrations in men with localized prostate cancer

Nutr Cancer. 2010;62(8):1036-43. doi: 10.1080/01635581.2010.492085.

Abstract

The efficacy and safety of consuming high-dose isoflavone supplements for prostate cancer is not clear. A double-blind, placebo controlled, randomized trial was conducted in 53 men with prostate cancer enrolled in an active surveillance program. The treatment group consumed a supplement containing 450 mg genistein, 300 mg daidzein, and other isoflavones daily for 6 mo. Prostate-specific antigen (PSA) was measured in both groups at baseline, 3 mo, and 6 mo, and serum concentrations of genistein, daidzein, and equol were assessed at baseline and 6 mo in the treatment group. Following the completion of the 6-mo double-blind study, men were enrolled in a 6-mo open label trial with the same isoflavone-rich supplement, and PSA was measured at 3 and 6 mo. PSA concentrations did not change in either group after 6 mo or after 12 mo when the open-label study was included. The 6 mo serum concentrations of genistein and daidzein (39.85 and 45.59 μmol/l, respectively) were significantly greater than baseline values and substantially higher than levels previously reported in other studies. Equol levels did not change. Although high amounts of aglycone isoflavones may result in significantly elevated serum concentrations of genistein and daidzein, these dietary supplements alone did not lower PSA levels in men with low-volume prostate cancer.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Antineoplastic Agents, Phytogenic / adverse effects
  • Antineoplastic Agents, Phytogenic / blood
  • Antineoplastic Agents, Phytogenic / chemistry
  • Antineoplastic Agents, Phytogenic / therapeutic use*
  • Biomarkers, Tumor / blood
  • Dietary Supplements* / adverse effects
  • Dietary Supplements* / analysis
  • Double-Blind Method
  • Equol
  • Genistein / adverse effects
  • Genistein / blood
  • Genistein / chemistry
  • Genistein / therapeutic use*
  • Humans
  • Isoflavones / adverse effects
  • Isoflavones / blood*
  • Isoflavones / therapeutic use*
  • Male
  • Middle Aged
  • Phytotherapy / adverse effects
  • Plant Extracts / adverse effects
  • Plant Extracts / chemistry
  • Plant Extracts / therapeutic use
  • Polysaccharides / adverse effects
  • Polysaccharides / chemistry
  • Polysaccharides / therapeutic use*
  • Prostate-Specific Antigen / blood*
  • Prostatic Neoplasms / blood
  • Prostatic Neoplasms / diet therapy*
  • Severity of Illness Index
  • Soybeans / chemistry
  • Time Factors

Substances

  • 4',7-dihydroxy-3,4-dihydroisoflavone
  • Antineoplastic Agents, Phytogenic
  • Biomarkers, Tumor
  • Isoflavones
  • Plant Extracts
  • Polysaccharides
  • genistein combined polysaccharide
  • Equol
  • daidzein
  • Genistein
  • Prostate-Specific Antigen