OBJECTIVES: The isoflavones present in red clover and soy are used as an alternative treatment for menopausal complaints and are commercially available as high-dose food supplements. These preparations contain varying amounts of active ingredients, often without detailed specifications. Thus, it is difficult to derive a recommended daily dose, and the reliability of these products is rather low. METHODS: We quantified the isoflavone content of 19 different isoflavone-containing preparations and compared their binding and transactivational activities with regard to estrogen receptor alpha, estrogen receptor beta, androgen receptor, progesterone receptor, peroxisome-proliferator-activated receptor, and aryl hydrocarbon receptor. RESULTS: The food supplements that we tested bound to and transactivated both the estrogen receptors and the other receptors. After comparing the isoflavone content quantified by us with the isoflavone content specified on the package labels, we found that at least the specified isoflavone content or more could be detected in only 5 of the 19 food supplements that we tested. CONCLUSIONS: Preparations containing isoflavones should be standardized for the isoflavone aglycone content to facilitate the prediction of theoretical hormonal activity, facilitate the intake of a controlled amount of isoflavones, and ensure greater product reliability.
OBJECTIVES: The isoflavones present in red clover and soy are used as an alternative treatment for menopausal complaints and are commercially available as high-dose food supplements. These preparations contain varying amounts of active ingredients, often without detailed specifications. Thus, it is difficult to derive a recommended daily dose, and the reliability of these products is rather low. METHODS: We quantified the isoflavone content of 19 different isoflavone-containing preparations and compared their binding and transactivational activities with regard to estrogen receptor alpha, estrogen receptor beta, androgen receptor, progesterone receptor, peroxisome-proliferator-activated receptor, and aryl hydrocarbon receptor. RESULTS: The food supplements that we tested bound to and transactivated both the estrogen receptors and the other receptors. After comparing the isoflavone content quantified by us with the isoflavone content specified on the package labels, we found that at least the specified isoflavone content or more could be detected in only 5 of the 19 food supplements that we tested. CONCLUSIONS: Preparations containing isoflavones should be standardized for the isoflavoneaglycone content to facilitate the prediction of theoretical hormonal activity, facilitate the intake of a controlled amount of isoflavones, and ensure greater product reliability.