(HealthDay News) — For men at high risk of biochemical recurrence after radical prostatectomy, daily consumption of a soy protein supplement is not associated with a reduction in the risk of recurrence, according to a study published in the July 10 issue of the Journal of the American Medical Association.

Maarten C. Bosland, D.V.Sc., Ph.D., from the University of Illinois at Chicago, and colleagues examined whether daily consumption of a soy protein isolate supplement for two years is associated with a reduction in the rate of biochemical recurrence of prostate cancer. Participants included 177 men at high risk of recurrence after radical prostatectomy for prostate cancer who were randomized to receive a daily serving of a beverage powder containing 20 g of protein in the form of soy protein isolate (87 men) or calcium caseinate (placebo; 90 men).

Following lack of treatment effects at a planned interim analysis, the trial was stopped early. The researchers found that 28.3 percent of participants developed biochemical recurrence within two years of entering the trial. Within the intervention and placebo groups, recurrence was 27.2 and 29.5 percent, respectively, with a hazard ratio for active treatment of 0.96 (log rank P = 0.89). There were no supplementation-related adverse events recorded, and adherence was more than 90 percent.

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“This randomized clinical trial demonstrated that development of biochemical recurrence of prostate cancer after radical prostatectomy was not reduced or delayed by daily consumption of a 20-g soy protein isolate supplement in men at high risk of recurrence, but the intervention appeared safe and was well tolerated,” the authors write.

One author disclosed financial ties to the pharmaceutical and biotechnology industries.

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