Daidzein metabolism

Frankenfeld CL, Atkinson C, Thomas WK, Gonzalez A, Jokela T, Wahala K, Schwartz SM, Li SS, Lampe JW. 2005. High concordance of daidzein-metabolizing phenotypes in individuals measured 1 to 3 years apart. Br J Nutr 94 873-876. 

Frankenfeld CL, McTiernan A, Aiello EJ, Thomas WK, LaCroix K, Schramm J, Schwartz SM, Holt VL, Lampe JW. 2004. Mammographic density in relation to daidzein-metabolizing phenotypes in overweight, postmenopausal women. Cancer Epidemiol Biomark Prev 13 1156-1162. 

Atkinson, C., Newton, K.M., Bowles, E.J.A., Yong, M., and Lampe, J.W. 2008. Demographic, anthropometric, and lifestyle factors and dietary intakes in relation to daidzein-metabolizing phenotypes among premenopausal women in the United States. Am J Clin Nutr 87, 679-687. 

Song, K.B., Atkinson, C., Frankenfeld, C.L., Jokela, T., Wahala, K., Thomas, W.K., and Lampe, J.W. 2006. Prevalenee of Daidzein-Metabolizing Phenotypes Differs between Caucasian and Korean American Women and Girls. J. Nutr. 136, 1347-1351. 

Recently, some of the specific faecal bacteria involved in the metabolism of dietary isoflavonoids were isolated (Hur et al., 2000). They have been shown to selectively convert genistin and daidzin to their respective aglycones. One of the isolated bacteria, under anoxic conditions, was further shown to metabolise genistein and daidzein to their respective dihydroxy-genistein and dihydroxy-daidzein. In the case of lignans, enterodiol and enterolactone were shown to be excreted in vivo only in rats harbouring a gut microflora (Rowland et al, 1999). 

The metabolism and bioavailability of isoflavonoids is likely to be of crucial importance to their ability to help protect human health against disease. Many studies have been published on the metabolism and bioavailability of isoflavones in adults. The metabolism of isoflavones is of particular interest because the potency of isoflavone metabolites differs from that of the parent compounds. The daidzein metabolite equol is three times as potent as is daidzein in an endometrial tumor line. Equol is also a more potent antioxidant in vitro (see Sections 7.3.5 and 7.4.2) ° and the clinical significance of the ability to form equol has been considered in depth. ... 

Interindividual variation in ability to metabolize daidzein to equol (more estrogenic and a more potent antioxidant than daidzein) could thus influence the potential health protective effects of soy isoflavones. The extent of gut microflora metabolism in humans is variable, approximately 35% of a Western population can produce equol. ... 

A variable metabolic response to isoflavones has been shown for subjects following consumption of soy flour urinary excretion concentrations of genistein, daidzein, equol, and O-DMA were increased 8-, 4-, 45-, and 66-fold, respectively, compared to baseline. Considerable interindividual variation in metabolic response was reported with the peak levels of equol showing the most variation. ... 

Intestinal microflora plays a key role in the metabolism and bioavailibility of isoflavones [86]. After ingestion, soybean isoflavones are hydrolyzed by intestinal glucosidases, which release the aglycones, daidzein and genistein, Fig. (16). 

Furthermore, the metabolism of isoflavones is influenced by different components of the diet. A high fiber diet may increase the growth and/or activity of bacteria responsible for equol production in the colon [90]. This is relevant since equol has an oestrogenic potency higher than the precursor daidzein [91]. 

Atkinson C, Frankenfeld CL, Lampe JW. 2005. Gut bacterial metabolism of the soy isoflavone daidzein Exploring the relevance to human health. Exp Biol Med (May-wood) 230 155-170. 

Fanti P, Sawaya PB, Custer LJ, Franke AA. 1999. Serum levels and metabolic clearance of the isoflavones genistein and daidzein in hemodialysis patients. J Am Soc Nephrol... 

Heinonen SM, Hoikkala A, Wahala K, Adlercreutz H. 2003. Metabolism of the soy isoflavones daidzein, genistein and glycitein in human subjects. Identification of new metabolites having an intact isoflavonoid skeleton. J Steroid Biochem Mol Biol 87 285-299. 

Kulling SE, Honig DM, Metzler M. 2001. Oxidative metabolism of the soy isoflavones daidzein and genistein in humans in vitro and in vivo. J Agric Food Chem 49 3024-3033. 

Genistein and daidzein directly affect testosterone metabolism, reducing the toxic metabolites of testosterone. Genistein, an isoflavone, also seems to slow or prevent the metastasis of invasive cancer cells. It is believed to work by preventing the formation of new blood vessels to cancerous tumors. Histoculture studies of genistein have shown that this phytochemical reduces the growth of prostatic cancer tissue. 

---