Daidzein plasma concentrations

VERKASALO P K, APPLEBY P N, ALLEN N E, DAVEY G, ADLERCREUTZ H AND KEY T J (2001) Soya intake and plasma concentrations of daidzein and genistein validity of dietary assessment among eighty British women (Oxford arm of the European Prospective Investigation into Cancer and Nutrition). 7 86 (3) 415-21. 

Similar plasma concentrations were detected for daidzein, genistein and equol in adults consuming modest quantities of soy foods containing about 50 mg/d of total isoflavones [91]. 

A summary of studies where some isoflavones and their metabolites have been analyzed from blood samples of sheep and cattle fed red clover is presented in Table 9.1. The concentrations of isoflavonoids seem to be at the same level in both sheep and cattle. Conjugated or total equol concentration varied between 33 and 770 xg per 100 mL, and free or unconjugated equol concentration was between 2 and 10 xg per 100 mL. Lundh (1995) has estimated that of the total equol concentration about 5% in cows and 1% in sheep exist as free. The plasma concentrations measured for conjugated formononetin, daidzein, genistein, or biochanin A were 1-55 jig per 100 mL. Concentrations for unconjugated forms were usually very small, less than 1 jig per 100 mL. 

Mean plasma isoflavone concentrations (after deconjugation) some 5 to 6h after consumption of soya-based foods have been reported as follows daidzein 0.5 to 3.1 p.M genistein 0.3 to 4.1 pM glycitein 0.20 to 0.85 Some data for the individual conjugates of... 

Knowledge of the pharmacokinetics of isoflavones in soy foods is essential for making recommendations regarding efficacy in clinical studies. Die plasma half-life of daidzein and genistein, measured from their plasma appearance and disappearance curves, is 7.9 h in adults peak concentrations occur 6-8 h after administration of the pure compounds [93] with peak concentrations ranging from 80 to 800 ng/ml (after a single oral dose of 50 mg of pure isoflavones). 

Gooderham, M.H., Adlercreutz, H., Ojala, S.T., Wahala, K., and Holub, B.J. 1996. A soy protein isolate rich in genistein and daidzein and its effects on plasma isoflavone concentrations, platelet aggregation, blood lipids and fatty acid composition of plasma phospholipid in normal men. JNutr 126, 2000-2006. 

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