A Combination of Tomato and Soy Products for Men With Recurring Prostate Cancer and Rising Prostate Specific Antigen

Abstract

Tomato and soy products are hypothesized to reduce the risk of prostate cancer or enhance efficacy of therapy. A study was completed to determine if men with active prostate cancer will adhere to a dietary intervention rich in tomato products and a soy protein supplement men (n = 41) with recurrent, asymptomatic prostate cancer were randomized among 2 groups: Group A (n = 20) consumed tomato products (no soy) for Weeks 0 through 4, targeting a minimum of 25 mg of lycopene/day. Group B (n = 21) consumed soy (no tomatoes) for Weeks 0 through 4, providing 40 g of soy protein/day. For Weeks 4 through 8, all men consumed a combined tomato-rich diet and soy supplements. No grade II through IV toxicities were observed. During Weeks 0 through 4, mean daily lycopene intake for Group A was 43 mg (± 15 mg) and mean soy intake for Group B was 39 g (± 1 g), remaining similar during Weeks 4 through 8. Serum lycopene increased from 0.72 ± 0.09 μ mol/l to 1.21 ± 0.10 μ mol/l (P < 0.0001) and urinary isoflavone excretion increased from not detectable to 54.1 ± 5.7 μ mol/l (P < 0.05) with 8 wk of diet intervention. Serum prostate-specific antigen decreased between Weeks 0 and 8 for 14 / 41 men (34%). Mean serum vascular endothelial growth factor for the entire group was reduced from 87 to 51 ng/ml (P < 0.05) over 8 wk. In conclusion, prostate cancer patients will consume diets rich in tomato products and soy with excellent compliance and bioavailability of phytochemicals. Further studies combining tomato and soy foods to determine efficacy for prostate cancer prevention or management are encouraged.

ACKNOWLEDGMENTS

This study was supported by The Ohio State University Comprehensive Cancer Center Grant P30 CA016058, National Cancer Institute Grant R01 CA112632, the Prostate Cancer Research Fund, and the Schoen Cancer Research Fund at the James Cancer Hospital and Solove Research Institute, The Ohio State University. The soy protein supplement was graciously provided by the Solae Company (St. Louis, MO).

Notes

^a N = 41. Abbreviations are as follows: BMI, body mass index; BP, blood pressure; BUN, blood urea nitrogen; Cr, creatinine; ALT, alanine aminotransferase; AST, aspartate aminotransferase; Bili, bilirubin; WBC, white blood cell; Hct, hematocrit; Hgb, hemoglobin.

^a Abbreviations are as follows: SEM, standard error of the measurement; ANOVA, analysis of variance. Means with different subscript letters are significantly different by ANOVA and pairwise comparisons (P < 0.05).

^a Abbreviations are as follows: SEM, standard error of the measurement; ND, not detectable; ODMA, O-desmethylangolensin; DHD, dihydrogenistein.

^b P value computed using an exact Wilcoxon signed rank test.

^c P value computed using an exact Wilcoxon rank sum test.

^d 5 men were equol producers: 1 in the tomato group, 4 in the soy group.

^a Abbreviations are as follows: PSA, prostate specific antigen; DT, doubling time.

^b Not enough data to accurately define DT in 1 man.