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See Latest ArticlesThe effect of genistein aglycone on cancer and cancer risk: a review of in vitro, preclinical, and clinical studies
Nutrition Reviews, 06/29/09
Taylor CK et al. - Clinical studies in osteopenic and osteoporotic, postmenopausal women support the breast and uterine safety of purified naturally derived genistein administered for up to 3 years. In this review, the authors summarize the in vitro, preclinical and clinical evidence for the safety of natural genistein.
Bruce P Burnett, 06/29/09
| Genistein aglycone from natural sources, in high concentrations (54 mg/day), has been shown to be a very bioactive molecule for both bone formation and management of vasomoter symptoms. Supplements usually contain minute quantities of this molecule and do not show the same bioactivity in clinical trials. In fact, a number of other isoflavones can antagonize genistein's activity in vivo preventing bone formation as well as vasomoter symptom management. Therefore, it is important to have a highly purified source of genistein aglycone to see biological effects. The long-term safety of this molecule is not known on women with breast cancer or a family history of reproductive cancer. In addition, animal studies have shown that genistein, at high concentrations, can result in urogenital defects in offspring. So its use should be limited to women who are unable to produce children. Finally, genistein interacts with CYP450 2C8 and 2C9 in in vitro human liver microsomal assays at a 10 micromolar concentration. It is still important to limit genistein's use to postmenopausal women who do not have a history of reproductive cancers as well as limiting genistein aglycone's use with other hormonal therapies such as estradiol or raloxifene. The interaction with other estrogen receptor binding agents is not known and caution should be practiced. It is also important to determine by pharmacokinetics if genistein in a particular product attains a concentration at which it may interact with drugs detoxified via 2C8 and 2C9. Different food, supplement, medical food and drug matrices are known to change genistein's PK profile. Only one product at present, Fosteum, a prescription medical food for the clinical dietary management of bone loss, has been shown to deliver doses below the drug interaction level (Burnett et al., submitted), while still maintaining activity. It is crucial that the proper cliniical trials be performed on all products containing high does of this promising, yet not completely characterized molecule in humans. It is also important to see a physician's input when taking products containing high doses of genistein as it may interact with other drugs. Supplements which do not test the drug toxicity profile or perform PK studies of their products should be avoided until they perform the proper safety testing. |
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