This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Several types of botanical products containing isoflavones are being marketed as an alternative to estrogen replacement therapy to prevent osteoporosis in postmenopausal women. Estrogen suppresses bone resorption and may increase calcium absorption. Efficacy of isoflavones on bone health has mixed results which may depend on the dose and interaction of isoflavones and the ability of individuals to produce equal. This project will determine the dose response of effect of genistein and the interaction with other soy isoflavones on calcium absorption and bone resorption in postmenopausal women who are equol vs. nonequol producers. We will use 41Ca, a long-lived isotope, to label the skeleton and an Accelerator Mass Spectrometry (AMS) to monitor perturbations by diet. This innovative approach to study bone resorption is a direct measure of bone resorption in contrast to biochemical markers of bone turnover and traditional calcium kinetics, rapid compared to studying changes in bone density, and not as invasive as bone histomorphometry. We are able to systematically determine the effect of various types and dosages of isoflavone-containing botanical products sequentially in the same postmenopausal women for their effectiveness in suppressing bone resorption by measuring changes in 41Ca excretion in the urine. As a positive control the effect of isoflavones will be compared to Actonel , a common osteoporosis treatment therapy.
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