Soya isoflavones

Kelly GE, Nelson C, Waring MA, Joannou GE, Reeder AY. 1993. Metabolites of dietary (soya) isoflavones in human urine. Clin Chim Acta 223 9-22. 

Hallund J, Bugel S, Tholstrup T, Ferrari M, Talbot D, Hall WL, Reimann M, Williams CM, Wiinberg N. 2006. Soya isoflavone-enriched cereal bars affect markers of endothelial function in postmenopausal women. Br J Nutr 95 1120-1126. 

Although cholesterol lowering is probably the best documented cardioprotective effect of soya, vascular protection is also likely to contribute and may be mediated via a number of mechanisms. Soya isoflavones are likely to contribute to the cardioprotective benefits of soya. 

Vascular protection could also be conferred by the ability of genistein to inhibit proliferation of vascular endothelial cells and smooth muscle cells and to increase levels of TGE-j8. TGE-j8 helps maintain normal vessel wall structure and promotes smooth muscle cell differentiation while preventing their migration and proliferation. Genistein has been shown to increase TGE-j8 secretion by ceUs in culture, and increased TGE-j8 production may be a mediator of some of the cardioprotective effects of soya isoflavones. 

In a 1996 review, the Committee of Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) estimated the intake of isoflavones from soya-milk to be approximately 4 mg/kg/day over the first 4 months of life. This is greater than that associated with hormonal effects in premenopausal women, but the COT nonetheless supported the existing Department of Health s advice that... 

Isoflavones Genistein Soya bean 64.8 US Department of Agriculture 2007b... 

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... 

Diets rich in millet have been associated with endemic goiter in parts of West Africa where millet is a staple. The damage has been attributed to vitexin, a C-glycosyl flavone, that in rats has antithyroid activity and that in vitro inhibits thyroid peroxidase and the free radical iodination step in thyroid hormone biosynthesis. Isoflavones have produced similar antithyroid effects in rats, but clinical studies in adults have not. " However, this remains a possible concern in infants fed soya-based milk-replacers, especially if iodine supply is compromised. 

Hoey, L., Rowland, I.R., Lloyd, A.S., Clarke, D.B., and Wiseman, H., Influence of soya-based infant formula consumption on isoflavone and gut microflora metabolite concentrations in urine and on faecal microflora composition and metabolic activity in infants and children, Br. J. Nutr, 91, 607, 2004. 

Few studies have been carried out in infants fed on soya formula. Absorption of isoflavones by the infant was demonstrated from the appearance of daidzein and genistein in the urine of 4-month-old infants fed soy formulas. Equol was not detected in the urine [94]. A later study by Setchell et al [95] did not confirm these results because equol was not detectable or present only in traces in the serum of 4-month-old infants fed soya infant formulas. Isoflavone concentration in human breast milk increased after the consumption of a soya-rich diet, but their contribution seems trivial in comparison to that from soy infant formulas [93]. 

Halm B, Ashburn L, Franke A. 2007. Isoflavones from soya foods are more bioavailable in children than adults. Br J Nutr 98 998-1005. 

Tsangalis D, Wilcox G, Shah NP, Stojanovska L. 2005. Bioavailability of isoflavone phytoestrogens in postmenopausal women consuming soya milk fermented with probiotic bifidobacteria. Br J Nutr 93 867-877. 

Yergne S, Bennetau-Pelissero C, Lamothe V, Chantre P, Potier M, Asselineau J, Perez P, Durand M, Moore N, Sauvant P. 2008. Higher bioavailability of isoflavones after a single ingestion of a soya-based supplement than a soya-based food in young healthy males. Br J Nutr 99 333-344. 

Isoflavones are derivatives of the parent compound isoflavone (3-phenylc,hromone 3-phenylbenzopyran-4-one). The dietary isoflavone phytoestrogens (notably from soya bean) that bind to the oestrogen receptor are the best known, namely daidzein (7,4 -dihydroxy-isoflavone), genistein (5,7,4 -trihydroxyisoflavone) and glycitein (7-hydroxy-6-methoxy-isoflavone) and their respective pro-phytoestrogen 7-0-glucoside precursors daidzin,... 

Duffy, R. Wiseman, H. File, S.E. Improved cognitive function in postmenopausal women after 12 weeks of consumption of a soya extract containing isoflavones. Pharmacol. Biochem. Behav. 2003, 75 (3), 721-729. 

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