| Many postmenopausal women are looking for | | | | suggest that Japanese women have a greater |
| alternatives to hormone therapy, especially in light | | | | risk of sustaining a vertebral fracture than |
| of the recent Women's Health Initiative research | | | | Caucasian women. |
| findings concerning the risks of combined estrogen | | | | Several studies have explored the effects of soy |
| and progestin therapy. Of particular interest are | | | | isoflavones on bone health, but results have been |
| phytoestrogens, which have been gaining | | | | mixed, ranging from a modest impact to no |
| popularity due to their "natural" status, alleged | | | | effect. Most of these studies have serious |
| health claims, and availability in a wide range of | | | | limitations, including their short duration and small |
| foods and supplements. | | | | sample size, making it difficult to fully evaluate the |
| What are Phytoestrogens? | | | | impact of these compounds on bone health. |
| Phytoestrogens are naturally occurring plant | | | | Ipriflavone Supplements |
| compounds that have some similarities to | | | | Ipriflavone, a synthetic isoflavone, has shown |
| estradiol, the most potent naturally occurring | | | | some promise in its ability to conserve bone in |
| estrogen. However, phytoestrogens tend to have | | | | postmenopausal women. Ipriflavone has also been |
| weaker effects than most estrogens, are not | | | | shown to have a protective effect on bone |
| stored in the body, and can be easily broken | | | | density in pre-menopausal women taking |
| down and eliminated. | | | | gonadotropin-releasing hormone (GnRH), a |
| Observational studies have found a lower | | | | treatment for endometriosis that triggers bone |
| prevalence of breast cancer, heart disease and | | | | loss. |
| hip fracture rates among people living in places like | | | | However, a definitive three-year study of more |
| Southeast Asia, where diets are typically high in | | | | than 400 postmenopausal women concluded that |
| phytoestrogens. In North America, knowledge of | | | | ipriflavone did not prevent bone loss. Additionally, |
| these reported health effects has stimulated | | | | the compound was linked to lymphocytopenia (a |
| great interest in the health benefits of | | | | reduction in lymphocytes) in a significant number |
| phytoestrogens. According to the Food and Drug | | | | of study participants. Lymphocytes are a type of |
| Administration, the sale of soy foods, a major | | | | white blood cell that helps the body fight infection. |
| source of phytoestrogens, has increased | | | | Risks and Benefits Are Unclear |
| dramatically in the past decade. | | | | Some studies suggest that, unlike estrogen, |
| Dietary Sources of Phytoestrogens | | | | phytoestrogens do not appear to target breast |
| Phytoestrogens consist of more than 20 | | | | or uterine tissue. This suggests that they may act |
| compounds and can be found in more than 300 | | | | more like SERMS (selective estrogen receptor |
| plants, such as herbs, grains and fruits. The three | | | | modulators such as raloxifene and tamoxifen) |
| main classes of dietary phytoestrogens are | | | | than actual estrogens. However, in other studies |
| isoflavones, lignans and coumestans:o Isoflavones | | | | high isoflavone levels have been linked to an |
| (genistein, daidzein, glycitein and equol) are | | | | increased risk of breast cancer. |
| primarily found in soy beans and soy products, | | | | Clearly, additional research is needed to further |
| chickpeas and other legumes.o Lignans | | | | evaluate the effects of phytoestrogens before |
| (enterolactone and enterodiol) are found in seeds | | | | judgments regarding their safety and usefulness |
| (primarily flaxseed), cereal bran, legumes, and | | | | can be made. |
| alcohol (beer and bourbon).o Coumestans | | | | Key Points |
| (coumestrol) can be found in alfalfa and clover. | | | | Based on information available at this time, it is |
| Most food sources containing these compounds | | | | reasonable to make the following conclusions |
| typically include more than one class of | | | | concerning phytoestrogens and bone health in |
| phytoestrogens. | | | | postmenopausal women:o Moderate amounts of |
| The Skeletal Effects of Phytoestrogens | | | | foods containing phytoestrogens can be safely |
| Much of the evidence concerning the potential role | | | | included in the diet but do not expect it to help |
| of phytoestrogens in bone health is based on | | | | build bone. Keep to the basic rule - eat the least |
| animal studies. In fact, soybean protein, soy | | | | processed forms.o Due to a lack of evidence and |
| isoflavones, genistein, daidzein and coumestrol | | | | concerns about safety, supplementation with |
| have all been shown to have a protective effect | | | | synthetic isoflavones (ipriflavone) is in question.o |
| on bone in animals who had their ovaries surgically | | | | Postmenopausal women are encouraged to view |
| removed. | | | | evidence concerning phytoestrogens and bone |
| In humans, however, the evidence is conflicting. | | | | health as conflicting and incomplete. For women |
| Compared to Caucasian populations, documented | | | | who are estrogen dominant increasing their |
| hip fracture rates are lower in countries such as | | | | phytoestrogen intake may not improve their bone |
| Hong Kong, China and Japan where dietary | | | | position. |
| phytoestrogen intakes are high. Yet reports | | | | |