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Prostatic soy isoflavone concentrations exceed serum levels after dietary supplementation.

ABSTRACT: The effects of soy isoflavones on prostate cancer may be concentration-dependent. The impact of soy supplementation on isoflavone concentrations in prostate tissues and serum remain unclear.To assess and compare concentrations of soy isoflavones in prostate tissue and serum among 19 men with prostate cancer who had elected to undergo radical prostatectomy.Participants were randomized to receive either daily soy supplements (82 mg/day aglycone equivalents) or placebos for 2 weeks (14 days) prior to surgery. Serum samples were obtained at the time of the surgery. Isoflavone concentrations were measured by HPLC/ESI-MS-MS.The median (25th, 75th percentile) total isoflavone concentration in the isoflavone-supplemented group was 2.3 micromol/L (1.2, 6.9) in the prostate tissue and 0.7 micromol/L (0.2, 1.2) in the serum. Total isoflavone concentrations in this group were an average of approximately 6-fold higher in prostate tissue compared to serum; the tissue versus serum ratio was significantly lower for genistein than daidzein, 4-fold versus 10-fold, P = 0.003. Tissue and serum levels of isoflavones among the placebo group were negligible with a few exceptions.The findings from the present study suggest that prostate tissue may have the ability to concentrate dietary soy isoflavones to potentially anti-carcinogenic levels.

SUBMITTER: Gardner CD

PROVIDER: S-EPMC2734961 | biostudies-literature | 2009 May

REPOSITORIES: biostudies-literature

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Prostatic soy isoflavone concentrations exceed serum levels after dietary supplementation.

Gardner Christopher D CD Oelrich Beibei B Liu Jenny P JP Feldman David D Franke Adrian A AA Brooks James D JD

The Prostate 20090501 7

<h4>Background</h4>The effects of soy isoflavones on prostate cancer may be concentration-dependent. The impact of soy supplementation on isoflavone concentrations in prostate tissues and serum remain unclear.<h4>Objective</h4>To assess and compare concentrations of soy isoflavones in prostate tissue and serum among 19 men with prostate cancer who had elected to undergo radical prostatectomy.<h4>Methods</h4>Participants were randomized to receive either daily soy supplements (82 mg/day aglycone ...[more]

PMID: 19180569

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Project description:S-(-)equol, an intestinally derived metabolite of the soy isoflavone daidzein, is proposed to enhance the efficacy of soy diets. Adults differ in their ability to produce equol when consuming soy foods for reasons that remain unclear. Therefore, we performed a comprehensive dietary analysis of 143 macro- and micronutrients in 159 healthy adults in the United States (n = 89) and Australia (n = 70) to determine whether the intake of specific nutrients favors equol production. Three-d diet records were collected and analyzed using Nutrition Data System for Research software and S-(-)equol was measured in urine by mass spectrometry. Additionally, in a subset of equol producers and nonproducers (n = 10/group), we examined the long-term stability of equol producer status by retesting 12, 18, and 24 mo later. Finally, the effect of oral administration of the antibiotic metronidazole (500 mg/d for 7 d) on equol production was examined in 5 adults monitored during a 4-mo follow-up period. Equol producers accounted for 30.3% and 28.6% of the United States and Australian participants, respectively (overall frequency, 29.6%). No significant differences were observed for total protein, carbohydrate, fat, saturated fat, or fiber intakes between equol producers and nonproducers. However, principal component analysis revealed differences in several nutrients, including higher intakes of polyunsaturated fatty acids (P = 0.039), maltose (P = 0.02), and vitamins A (P = 0.01) and E (P = 0.035) and a lower intake of total cholesterol (P = 0.010) in equol producers. During a 2-y period, equol producer status remained unchanged in all nonproducers and in 80% of equol producers, whereas metronidazole abolished equol production in only 20% of participants. In conclusion, these findings suggest that major differences in the macronutrient content of the diet appear not to influence equol production, but subtle differences in some nutrients may influence the ability to produce equol, which was a relatively stable phenomenon.

Dataset Information

Prostatic soy isoflavone concentrations exceed serum levels after dietary supplementation.

Publications

Prostatic soy isoflavone concentrations exceed serum levels after dietary supplementation.

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