Impact of one-year soy protein supplementation on serum metabolomic profiles: results from a randomized, placebo-controlled trial in prostate cancer patients

Purpose This study aims to investigate global metabolomic effects of soy protein supplementation. Design/methodology/approach This study was designed as an exploratory study based on residual specimens from a randomized placebo-controlled trial. The authors investigated changes in serum metabolomic and lipidomic profiles of prostate cancer patients who were assigned to soy protein (19.2 g/day, 41 mg isoflavones, n = 10) or a casein-based placebo (19.8 g/day n = 11) for up to one year following prostatectomy. A total of 63 serum samples collected at baseline, 6 and 12 months were analyzed by untargeted, global metabolomics. Findings Partial least squares discriminant analysis, based on 493 polar metabolites and 4,706 lipids, showed clear separation of changes in metabolomic profiles between the soy and placebo groups. However, the only metabolite that was significantly different after multiple comparison adjustment was daidzein 4′–sulfate (p = 0.036). A few other metabolites/lipids were weakly associated with soy supplementation; betaine and C18-ceramide derivative increased and l-α-aminoadipic acid and a linolenic acid derivative decreased, compared with the placebo. Originality/value The present study demonstrates that physiologically relevant dietary levels of soy protein supplementation close to real-life levels of consumption lead to a shift in global metabolomic profiles.