Impact of 18-Month Soy Protein Supplementation on Steroid Hormones and Serum Biomarkers of Angiogenesis, Apoptosis, and the Growth Hormone/IGF-1 Axis: Results of a Randomized, Placebo-Controlled Trial in Males Following Prostatectomy.

2021-01-12
Nutrition and cancer 74(1)
- Maarten C Bosland
- Jonathan Huang
- Michael J Schlicht
- Erika Enk
- Hui Xie
- Ikuko Kato

PubMed: 33432829
DOI: 10.1080/01635581.2020.1870706

Study Design

Type: Randomized Controlled Trial (RCT)
Population: middle-aged to older males at risk of recurrence of prostate cancer after radical prostatectomy
Methods: two-year trial of soy protein isolate supplementation; compared with a casein-based placebo, 18 mo of consumption of 19.2 g/day of whole soy protein isolate containing 24 mg genistein
Blinding: Double-blind
Duration: 2 years

Many studies have addressed the effects of dietary supplementation with soy protein on cancer risk and mortality, but there are only few randomized studies with soy in males. We used serum samples from a two-year trial of soy protein isolate supplementation in middle-aged to older males at risk of recurrence of prostate cancer after radical prostatectomy to determine soy effects on steroid hormones involved in prostate cancer (testosterone, SHBG, and estradiol) and explore the effects on biomarkers of the growth hormone/IGF-1 axis, apoptosis, and angiogenesis. Compared with a casein-based placebo, 18 mo, of consumption of 19.2 g/day of whole soy protein isolate containing 24 mg genistein-reduced circulating testosterone and SHBG, but not free testosterone, and did not affect serum concentrations of estradiol, VEGF, IGF-1, IGFBP-3, IGF-1/IGFBP-3 ratio, soluble Fas, Fas-ligand, and sFas/Fas-ligand ratio. Thus, soy protein supplementation for 18 mo, affected the androgen axis, but the effects on other cancer biomarkers remain to be more definitively determined. The study was registered at clinicaltrials.gov (NCT00765479).

Research Insights

Soy Protein→Reduced Estradiol Level
did not affect serum concentrations of estradiol
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Fas Ligand Level
did not affect serum concentrations of ... Fas-ligand
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Free Testosterone Level
did not affect serum concentrations of ... free testosterone
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced IGF-1 Level
did not affect serum concentrations of ... IGF-1
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Insulin-Like Growth Factor 1 Level
did not affect serum concentrations of ... IGF-1
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Insulin-Like Growth Factor 1 to Insulin-Like Growth Factor Binding Protein 3 Ratio
did not affect serum concentrations of ... IGF-1/IGFBP-3 ratio
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Insulin-Like Growth Factor-Binding Protein 3 Level
did not affect serum concentrations of ... IGFBP-3
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Insulin-like Growth Factor-1/Insulin-like Growth Factor Binding Protein-3 Ratio
did not affect serum concentrations of ... IGF-1/IGFBP-3 ratio
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced SHBG
18 mo, of consumption of 19.2 g/day of whole soy protein isolate containing 24 mg genistein-reduced circulating testosterone and SHBG
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Sex Hormone-Binding Globulin Level
18 mo of consumption of 19.2 g/day of whole soy protein isolate containing 24 mg genistein reduced circulating testosterone and SHBG, but not free testosterone
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Soluble Fas Level
did not affect serum concentrations of ... soluble Fas
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Soluble Fas Ligand Level
did not affect serum concentrations of ... Fas-ligand
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Soluble Fas to Fas Ligand Ratio
did not affect serum concentrations of ... sFas/Fas-ligand ratio
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Soluble Fas/Fas Ligand Ratio
did not affect serum concentrations of ... sFas/Fas-ligand ratio
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Testosterone Level
18 mo of consumption of 19.2 g/day of whole soy protein isolate containing 24 mg genistein reduced circulating testosterone and SHBG, but not free testosterone
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Vascular Endothelial Growth Factor
did not affect serum concentrations of ... VEGF
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein
Soy Protein→Reduced Vascular Endothelial Growth Factor Level
did not affect serum concentrations of ... VEGF
Effect
Neutral
Effect size
Small
Dose
19.2 g/day of whole soy protein isolate containing 24 mg genistein