Original Article
European Journal of Clinical Nutrition (2006) 60, 1039–1045. doi:10.1038/sj.ejcn.1602415; published online 15 February 2006
One-month exposure to soy isoflavones did not induce the ability to produce equol in postmenopausal women
N Védrine1, J Mathey2, C Morand2, M Brandolini3, M-J Davicco2, L Guy1, C Rémésy2, V Coxam2 and C Manach2
- 1CHRU Clermont-Ferrand, Service Urologie, Clermont-Ferrand, France
- 2Unité des Maladies Métaboliques et Micronutriments, INRA Clermont-Theix, St-Genès Champanelle, France
- 3Laboratory of Human Nutrition, CRNH d'Auvergne, Clermont-Ferrand, France
Correspondence: Dr C Manach, Unité des Maladies Métaboliques et Micronutriments, INRA Clermont-Theix, St-Genès Champanelle 63122, France. E-mail: manach@clermont.inra.fr
Received 19 September 2005; Revised 16 December 2005; Accepted 5 January 2006; Published online 15 February 2006.
Abstract
Objective:
As more and more postmenopausal women are taking soy isoflavone supplementation for relieving menopausal symptoms, we investigated the impact of chronic exposure on their bioavailability, with focus on achievable plasma concentrations and potential stimulation of the capacity to produce equol.
Subjects:
A total of 12 Caucasian postmenopausal women.
Intervention:
Volunteers ingested 100 mg isoflavones/day (aglycone equivalents, in cereal bars and yoghurts) for 1 month. Plasma concentrations of metabolites at 2, 4, 6, 8, 10, 12 and 24 h postdose, as well as urinary excretion in fractions over 36 h were compared between days 1 and 30.
Results:
Similar plasma kinetic curves were obtained at day 1 and day 30 for genistein and daidzein. Maximum plasma concentrations were 1.68
0.68 
mol/l on day 1 compared to 2.270.76 mol/l on day 30 for daidzein (P=0.056), and 3.881.50 mol/l on day 1 compared to 5.302.38 mol/l on day 30 for genistein (P=0.091). Urinary excretion of daidzein and genistein did not differ significantly between days 1 and 30. Maximum plasma concentration of equol increased significantly from 0.310.27 to 0.990.51 mol/l for equol-producer volunteers (P=0.046). However, the seven volunteers who were classified as non-equol producers on day 1 did not acquire the ability to produce equol after 1-month exposure.
Conclusions:
Chronic exposure to isoflavones in postmenopausal women resulted in plasma concentrations as high as 2.5–5 mol/l of each isoflavone, but did not induce the ability to produce equol.
Sponsorship:
French Ministry of Research (AQS program A01347) and Beghin-Meiji (doctoral fellowship).
Keywords:
isoflavones, genistein, equol, pharmacokinetics, chronic exposure, dietary supplements
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