In Reply Dr Moyad questions the choice of the intervention and placebo products in our trial of the effect of soy protein on biochemical recurrence of prostate cancer after radical prostatectomy.
The intervention was not purely soy protein isolate, but soy protein was the only component that was different between the intervention and placebo products. Both products were sweetened with sucrose and fructose to ensure acceptable palatability of the soy isolate. Inclusion of sugars did not introduce bias since the products contained the same amounts and there is no evidence that carbohydrate consumption affects PSA or biochemical recurrence. We agree that it is important to assess other effects of soy protein (eg, serum cholesterol levels) and will report these end points in the future.
Bosland MC, Kato I, Zeleniuch-Jacquotte A. Soy Protein and Recurrence of Prostate Cancer—Reply. JAMA. 2013;310(21):2312-2313. doi:10.1001/jama.2013.278613