Long-Term Dietary Habits Affect Soy Isoflavone Metabolism and Accumulation in Prostatic Fluid in Caucasian Men
Open Access
- 1 June 2005
- journal article
- research article
- Published by Elsevier in Journal of Nutrition
- Vol. 135 (6), 1400-1406
- https://doi.org/10.1093/jn/135.6.1400
Abstract
The soy isoflavones daidzein and genistein are believed to reduce prostate cancer risk in soy consumers. However, daidzein can be metabolized by the intestinal flora to form a variety of compounds with different bioactivities. In the current study, we investigated the influence of long-term dietary habits on daidzein metabolism in healthy Caucasian men (19–65 y old). A secondary goal was to compare plasma and prostatic fluid concentrations of 5 isoflavonoids: genistein, daidzein, equol, dihydrodaidzein, and O-desmethylangolensin. Baseline plasma levels of isoflavonoids were quantitated in 45 men by HPLC-electrospray ionization-MS. Participants then consumed a soy beverage daily for 1 wk, and post-soy isoflavonoid levels were quantitated in plasma and prostatic fluid. Equol was the only metabolite that appeared to be influenced by routine dietary habits. Stratified analyses revealed that men who had consumed ≥30 mg soy isoflavones/d for at least 2 y had 5.3-times the probability of producing equol than men who had consumed ≤5 mg/d (P = 0.014). Additionally, those men who consumed animal meat regularly had 4.7-times the probability of producing equol than men who did not consume meat (P = 0.023). Equol production was not linked to age, BMI, or the consumption of yogurt, dairy, fruit, or American-style fast food. Daidzein and its metabolites (but not genistein) were typically present at higher levels in prostate fluid than plasma (median = 4–13 times that in plasma). In conclusion, our data suggest that the ability of Caucasian men to produce equol is favorably influenced by the long-term consumption of high amounts of soy and the consumption of meat. Last, the high concentrations of isoflavonoids in prostatic fluid increases the potential for these compounds to have direct effects in the prostate.Keywords
This publication has 36 references indexed in Scilit:
- Evidence that soyasaponin Bb retards disease progression in a murine model of polycystic kidney diseaseKidney International, 2003
- Soy isoflavonoid equol modulates the growth of benign and malignant prostatic epithelial cells in vitroThe Prostate, 2002
- THE EFFECT OF ISOLATED SOY PROTEIN ON PLASMA BIOMARKERS IN ELDERLY MEN WITH ELEVATED SERUM PROSTATE SPECIFIC ANTIGENJournal of Urology, 2001
- Effect of soy‐derived isoflavonoids on the induced growth of MCF‐7 cells by estrogenic environmental chemicalsNutrition and Cancer, 1998
- Measurement and metabolism of isoflavonoids and lignans in the human maleCancer Letters, 1997
- The role of metabolism in mammary epithelial cell growth inhibition by the isoflavones genistein and biochanin ACarcinogenesis: Integrative Cancer Research, 1996
- Phytoestrogens: epidemiology and a possible role in cancer protection.Environmental Health Perspectives, 1995
- Metabolites of dietary (soya) isoflavones in human urineClinica Chimica Acta; International Journal of Clinical Chemistry, 1993
- Inhibition of human aromatase by mammalian lignans and isoflavonoid phytoestrogensThe Journal of Steroid Biochemistry and Molecular Biology, 1993
- Effect of dietary components, including lignans and phytoestrogens, on enterohepatic circulation and liver metabolism of estrogens and on sex hormone binding globulin (SHBG)Journal of Steroid Biochemistry, 1987