Isoflavones in treating watchful waiting benign prostate hyperplasia: a double-blinded, randomized controlled trial

This study aims to determine the efficacy and safety of soy isoflavones in controlling the symptoms and signs of lower urinary tract symptoms due to benign prostate hyperplasia (BPH).

This was a prospective, randomized, double-blind, placebo-controlled pilot study.

This trial was conducted at two hospitals in Hong Kong between May 2006 and September 2007.

One hundred and seventy-six (176) participants diagnosed with BPH were recruited from outpatient clinics. Participants with lower urinary tract symptoms were recruited through newspaper and radio interviews, posters placed at government outpatient clinics, and a public seminar offered by the investigators.

Participants were randomly assigned to either intervention (40 mg of isoflavones daily from Soylife 40) or placebo groups in a double-blind fashion.

The primary outcome parameter of peak urine flow rate and the second outcome parameters of postresidual urine volume, lower urinary tract symptoms, testosterone, prostate-specific antigen, quality of life, diet, and safety profile (liver and renal function) were collected. All parameters were assessed at baseline, 6 months, and 12 months in a 12-month study period except testosterone, prostate-specific antigen, and safety profile, which were assessed at baseline and at 12 months.

The peak urine flow rate (Qmax), postresidual urine volume, International Prostate Symptoms Scores (IPSS), and 36-Item Short Form Health Survey (SF-36) significantly improved from baseline to the 12th month within both groups. However, when compared between groups, Qmax (p=0.055) and incomplete emptying subscore in IPSS (p=0.05) were marginally/statistically different between the two groups from the 6th to the 12th months, in addition to the general health domain of SF-36 from the baseline to 12th month (p=0.02) and from the 6th month to the 12th month (p=0.055). Isoflavones were generally safe and well tolerated.

This randomized control pilot study showed only slight superiority of isoflavones over placebo over 12 months with otherwise surprising beneficial effects in both groups. Tolerability of isoflavones was excellent; thus it has laid foundations for further studies of isoflavones in BPH with focus on dosage and possible specificity of the effect.