Dietary_Supplements___Soy - Dietary Supplements Soy...

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Dietary Supplements - Soy Soy Protein Background In Asian countries there is a much lower incidence of of cardiovascular disease, menopausal symptoms, as well as some cancers than in the United States. Some of these reduced rates can be attributable to differences in diet. One major difference is the high consumption of soy protein in these cultures. Interesting enough, the majority of the world's soybeans are grown in the US, yet most of the crop is exported. The average American consumes about 3 mg/day of soy compounds compared to the Japanese who consume 40 - 100 mg daily(1). Phytoestrogens are the non-steroidal active compounds in soy which give it its therapeutic properties. Two main classes of phytoestrogens are lignans and isoflavones. The isoflavone compounds found in soy are primarily comprised of genistein and daidzein, which are responsible for the effects seen with consumption of soy protein. Dietary sources of lignans and isoflavones include flaxseed and soybeans and other soy products, respectively. Soybeans were first recognized to contain isoflavones about 65 years ago, and much attention has been given to isoflavones more recently because of their prevalence in soy products. Phytoestrogens primarily act as estrogen mimics. Because of this feature they can act as an estrogen agonist or antagonist, depending on the amount of endogenous (made by the body) estrogen present and type of cell they are acting on (2). However the effects of these "dietary" estrogens are 2-3 fold lower than that of endogenous estrogen, thereby lowering the body's exposure to the effects of estrogen (2). Phytoestrogens also have non hormonal properties such as regulating cell proliferation. Absorption Phytoestrogens of dietary origin are biotransformed in the intestine by the action of bacterial enzymes in the intestinal flora. The phytoestrogens are then converted to equol, which is absorbed along with unconverted genistein and daidzein (2). The response to soy can vary from person to person depending on the extent of bacterial metabolism. Purported Health Effects Relief of Menopausal Symptoms In the absence of endogenous estrogen, such as in the menopausal state, phytoestrogens can bind to the estrogen receptors and increase estrogen activity. But when estrogen levels are high (pre-menopausal state) the phytoestrogens compete with endogenous estrogens for the estrogen receptor sites and cause and overall decrease in estrogen activity. Soy may be responsible for modifying the frequency and duration of hot flashes, but it does not seem to have an effect on any
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This note was uploaded on 06/09/2010 for the course MFC 141 taught by Professor Horvath during the Summer '10 term at SUNY Buffalo.

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Dietary_Supplements___Soy - Dietary Supplements Soy...

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