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SECOND INTERNATIONAL SYMPOSIUM
ON THE ROLE OF SOY
IN PREVENTING AND TREATING CHRONIC DISEASE
September 15-18, 1996
Metabolism of Isoflavononoids in Japanese Men
H. Adlercreutz, K. Wähälä*, S. Rasku*, A. Salakka* and S. Watanabe**
Department of Clinical Chemistry and *Chemistry, University of Helsinki, Helsinki, Finland
** Department of Nutrition and Epidemiology, Faculty of Nutritional Science, Tokyo University of Agriculture, Tokyo, Japan.
Due to the intake of various soy products Japanese men have high urinary and plasma concentrations of isoflavonoids. However, without knowing the fecal excretion of these compounds it is not possible to obtain a picture of the overall metabolism of these compounds. Utilizing new isotope dilution GC-MS methods for phytoestrogens we measured plasma, urinary and fecal isoflavonoids in 30 Japanese men consuming a normal Japanese diet. The following fecal values were found: Daidzein (Da) (22-14300; mean 13279 nmol/24h), O-desmethylangolensin (O-Dma) (0-10200; mean 1845), equol (Eq) (0-21900; mean 5752) and genistein (Gen) (4.3-8860; mean 7409). The fecal proportion of total excretion in urine + feces of Da, O-Dma, Eq and Gen was 12.4% for Da, 27.9% for O-Dma, 32.3 % for Eq and 10.1% for Gen. Urinary and plasma Eq was found in all 30 subjects and fecal Eq in 28 subjects. Low Eq values in urine (<100 nmol/24h) were found in 8 (26.7 %), and in feces (<50 nmol/24h) in 9 (30%) subjects. Eq was detected in all plasma samples. The total urinary + fecal excretion of isoflavonoids was 28.3 mol/24h (about 7.2 mg/24h of isoflavonoids) (range 5.55-69.1 mol/24h). Of this 20.8 mol/24h was Da and its metabolites and 7.41 mol/24h was genistein. Plasma mean Da, O-Dma, Eq and Gen values were 257, 25.9, 38.4 and 418 nmol/l. Fecal and urinary individual isoflavonoids correlated very well (p<0.001), but only plasma O-Dma and Eq and not Da and Gen correlated significantly with the corresponding urinary (p<0.001) and fecal values (p<0.001), indicating extensive metabolism of Da and Gen. There was a slight negative correlation between urinary (r=-0.22 and fecal Eq (r=-0.20) and urinary O-Dma, but these were not significant (p>0.1). Fecal Eq and O-Dma did not show any correlation. However, there was a significant negative correlation between fecal Da and urinary Eq (r=0.48; p<0.01).
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