A Novel Tomato-Soy Juice Induces a Dose-Response Increase in Urinary and Plasma Phytochemical Biomarkers in Men with Prostate Cancer

J Nutr. 2019 Jan 1;149(1):26-35. doi: 10.1093/jn/nxy232.

Abstract

Background: Tomato and soy intake is associated with reduced prostate cancer risk or severity in epidemiologic and experimental studies.

Objective: On the basis of the principle that multiple bioactives in tomato and soy may act on diverse anticancer pathways, we developed and characterized a tomato-soy juice for clinical trials. In this phase 2 dose-escalating study, we examined plasma, prostate, and urine biomarkers of carotenoid and isoflavone exposure.

Methods: Men scheduled for prostatectomy were recruited to consume 0, 1, or 2 cans of tomato-soy juice/d before surgery (mean ± SD duration: 24 ± 4.6 d). The juice provided 20.6 mg lycopene and 66 mg isoflavone aglycone equivalents/177-mL can. Plasma carotenoids and urinary isoflavone metabolites were quantified by HPLC-photometric diode array and prostate carotenoids and isoflavones by HPLC-tandem mass spectrometry.

Results: We documented significant dose-response increases (P < 0.05) in plasma concentrations of tomato carotenoids. Plasma concentrations were 1.86-, 1.69-, 1.73-, and 1.69-fold higher for lycopene, β-carotene, phytoene, and phytofluene, respectively, for the 1-can/d group and 2.34-, 3.43-, 2.54-, and 2.29-fold higher, respectively, for the 2-cans/d group compared with 0 cans/d. Urinary isoflavones daidzein, genistein, and glycitein increased in a dose-dependent manner. Prostate carotenoid and isoflavone concentrations were not dose-dependent in this short intervention; yet, correlations between plasma carotenoid and urinary isoflavones with respective prostate concentrations were documented (R2 = 0.78 for lycopene, P < 0.001; R2 = 0.59 for dihydrodaidzein, P < 0.001). Secondary clustering analyses showed urinary isoflavone metabolite phenotypes. To our knowledge, this is the first demonstration of the phytoene and phytofluene in prostate tissue after a dietary intervention. Secondary analysis showed that the 2-cans/d group experienced a nonsignificant decrease in prostate-specific antigen slope compared with 0 cans/d (P = 0.078).

Conclusion: These findings provide the foundation for evaluating a well-characterized tomato-soy juice in human clinical trials to define the impact on human prostate carcinogenesis. This trial is registered at clinicaltrials.gov as NCT01009736.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aged
  • Beverages / analysis*
  • Biomarkers / blood
  • Carotenoids / chemistry
  • Humans
  • Lycopersicon esculentum*
  • Male
  • Middle Aged
  • Phytochemicals / blood*
  • Phytochemicals / urine*
  • Prostate / chemistry
  • Prostatic Neoplasms / blood
  • Prostatic Neoplasms / metabolism*
  • Prostatic Neoplasms / urine
  • Soybean Proteins*

Substances

  • Biomarkers
  • Phytochemicals
  • Soybean Proteins
  • Carotenoids

Associated data

  • ClinicalTrials.gov/NCT01009736