Soy isoflavonoids

Further to the possible contribution that soy isoflavonoids may make to adult human health, the possible health consequences of early life soy exposure are also attracting atten-... 

Coenzyme QIO Melatonin DHEA Acetylcarnitine SAMe n-3-Fatty acids Carotenoids, e.g., lutein/lycopene Carotenoids, e.g., lutein/lycopene n-3-Fatty acids Soy isoflavonoids/protein Green tea extracts Octacosanol/policosanol Resveratrol Pycnogenol Glucosamine Chondroitin MSM... 

Figure 38.2 Possible sites of inhibitory actions of soy isoflavones on iodine utilization and thyroid hormone biosynthesis and actions. Soy isoflavonoids, genistein and daidzein, inhibit oxidation of iodide by thyroid peroxidase at the apical membrane of thyroid follicular cells, followed by iodination of tyrosine residues in thyroglobulin and their coupling in colloid. In addition, they may affect deiodination of iodothyronines and interfere with thyroid hormone binding to transthyretin. Full arrows indicate the sites of inhibition. So far, only few reports concern the effect of thyroid hormone actions in target cells.

Clinical Trials Potential benefits and risks of high soy food consumption, the use of soy isoflavonoids in food supplements, as well as previous observations of the influence of soy-based formulas on hormonal balance and... 

Barnes, S. et al.. Soy isoflavonoids and cancer prevention Underlying biochemical and pharmacological issues, in Dietary Phytochemicals and Cancer Prevention, Butrum, R., Ed., Plenum Press, New York, 1996, 87. 

HEDLUND, T.E., JOHANNES, W.U., MILLER, G.J., Soy isoflavonoid equol modulates the growth of benign and malignant prostatic epithelial cells in vitro. Prostate, 2003, 54, 68-78. 

McCue, P. and Shetty, K. 2004. Health benefits of soy isoflavonoids and strategies for enhancement a review. Crit Rev. Food Sci. Nutr., 44. 361 367. 

Chua, R., Anderson, K., Chen, J., and Hu, M. 2004. Quality, labeling accuracy, and cost comparison of purified soy isoflavonoid products. J Ahern Complement Med 10, 1053-1060. 

HUTCHINS A M, SLAVIN J L and LAMPE I w (1995) Urinary isoflavonoid phytoestrogen and lignan excretion after consumption of fermented and imfermented soy products. JAm Diet Assoc 95, 545-51. 

SLAVIN J L, KARR s c, HUTCHINS A M and LAMPE J w (1998) Influence of soybean processing, habitual diet, and soy dose on urinary isoflavonoid excretion. Am J Clin Nutr 68, 1492S-5S. 

CHEN z, ZHENG w, CUSTER L J, DAI Q, SHU X o, JIN F and FRANKE A A (1999) Usual dietary consumption of soy foods and its correlation with the excretion rate of isoflavonoids in overnight urine samples among Chinese women in Shanghai. Nutr Cancer. 33 (1) 82-7. 

NAKAMURA Y, TSUJi s and TONOGAi Y (2000) Determination of the levels of isoflavonoids in soybeans and soy-derived foods and estimation of isoflavonoids in the Japanese daily intake. JAOAC Int. 83 (3) 635-50. 

SEOW A, SHI c Y, FRANKE A A, HANKIN J H, LEE H P and YU M c (1998) Isoflavonoid levels in spot urine are associated with frequency of dietary soy intake in a population-based sample of middle-aged and older Chinese in Singapore. Cancer Epidem Biomarkers Prev. 1 (2) 135-40. 

Before 1990 the composition of isoflavones in soy foods was thought to be largely determined by whether the food had been fermented. Fermented foods (e.g., miso and tempeh) contain the unconjugated isoflavones agycones, while non-fermented food (e.g., tofu, soy flower, and soy milk) contain the conjugated glucoside. Subsequent experiments have demonstrated that fermentation of soy decreased the isoflavone content of the food product, but increased the urinary isoflavonoid recovery, suggesting that fermentation increases availability of isoflavones in soy (Slavin et al., 1998). 

Three cohort studies have been performed, one in European women, and two in oriental women eating a traditional soy-based diet. The study in European women, performed by Kardinaal et al. (1998), failed to show a correlation between change in forearm bone mineral density and urinary excretion of isoflavonoids. Excretion of enterolactone, a marker of intake of grain and berries, was found to correlate positively with bone mineral density. This may be explained with the difficulty of correlating bone mineral density -a multifactorial variable, influenced by diet only on long-term basis - with excretion of phytoestrogens that only quantify the last 24 to 48 hours of phytoestrogen intake. 

Isoflavonoids include the isoflavones genistein and daidzein, which occur mainly as the glycosides genistin and daidzin (see Figure 7.2), respectively, in soybeans and consequently in a wide range of soy-derived foods and to a lesser extent in other legumes. Traditional... 

FIGURE 7.2 Chemical structures of the main soy (genistein and daidzein) and red clover (biochanin A and formononetin) isoflavonoids (aglycones and glucosides). 

The possible role of isoflavonoids in the prevention of cancer and in particular hormone-dependent cancers such as breast and prostate cancer is currently extensively investi-gated. " " In addition, consumption of soy foods rich in isoflavones has been weakly associated with reduced colon cancer. Colon cancer risk is influenced by estrogen exposure although the mechanism of action has not been fully elucidated, studies with estrogen receptor a (see Section 7.3.3) knockout mice indicate that it may be independent of estrogen receptor... 

Lower incidence of heart disease has also been reported in populations consuming large amounts of soy products. Lowering of cholesterol is probably the best-documented cardioprotective effect of soy. ° Soy protein incorporated into a low-fat diet can reduce cholesterol and LDL-cholesterol concentrations and the soy isoflavones are likely to contribute to these effects. Soy isoflavones have been reported to improve cardiovascular risk factors in peripubertal rhesus monkeys, and inflammatory markers in atherosclerotic, ovariecto-mized monkeys. The potential role of phytoestrogens, including isoflavonoids, as cardioprotective agents has been extensively reviewed." ... 

Wiseman H, Casey K, Bowey EA et al. Influence of 10 wk of soy consumption on plasma concentrations and excretion of isoflavonoids and on gut microfiora metabolism in healthy adults. Am. J. Clin. Nutr. 80, 692-699, 2004. 

Halm BM, Franke AA, Ashbum LA, Hebshi SM, Wilkens LR. 2008. Oral antibiotics decrease urinary isoflavonoid excretion in children after soy consumption. Nutrition... 

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. 

Jaceldo-Siegl K, Fraser GE, Chan J, Franke AA, Sabate J. 2008. Validation of soy protein estimates from a food-frequency questionnaire with repeated 24-h recalls and isoflavonoid excretion in overnight urine in a western population with a wide range of soy intakes. Am J Clin Nutr 87 1422-1427. 

Although isoflavones are present in several species of legumes, most of the research has been on soybean and soybean foods, due to the widespread use of soybean in traditional and modem foods (Liu, 1997 Messina, 1997). Recently, the Food and Drug Administration (FDA) approved a health claim for the relationship between the consumption of soy protein and heart disease (Federal Register, 1999). This approval further encourages soy isoflavone research. There may be health claims that could be made in the future to associate the intake of the isoflavonoids and the lowering of the risk of certain chronic diseases. 

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