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PHYTOESTROGENS
Phytoestrogens are a
diverse group of nonsteroidal compounds found in a variety of plant foods.
They have both estrogenic and antiestrogenic effects, and whether they act
primarily as an estrogen or antiestrogen depends on the individual's amount
of circulating endogenous estrogensand the number and type of estrogen receptors.3
They
are categorized according to their chemical structures as isoflavones (the
most potent), coumestans and lignans. All pyhytoestrogens have in common a
phenolic group similar to that of estrogenic steroids. Observational data
has shown that Asian women who consume more soy in their diet have decreased
incidence of osteoporosis, breast cancer, and cardiovascular disease when
compared to their European counterparts. Soy products also reduce LDL and
triglyceride concentrations. 
There are more than 1000 types of isoflavones, but the most commonly investigated are genistein and daidzein, which are also thought to have the highest estrogenic properties. They are found in legumes such as soy, chickpeas, clover, lentils, and beans. The amount of phytoestrogen found in each soy protein depends on the processing techniques used and its relative abundance in the specific soy product of interest. The secondary soy products (milk or flour) contain lower amounts of isoflavones than the primary products.3
Use of phytoestrogens may not be without side-effects, they have been found to affect concentrations of thyroxine, insulin, and glucagon.3 Although the evidence of benefits from phytoestrogens is increasing, many questions regarding their long-term efficacy and safety as substitutes for traditional ERT remain unanswered, since no human trials are available at the present time.
Ipriflavone is a synthetic nonhormonal drug with antiresorptive properties and is currently approved for treatment of osteoporosis in European and Asian countries.4 Recent reviews summarize the efficacy and safety of ipriflavone in protecting against bone loss in early menopause, in postmenopausal women with low bone mass, and in elderly osteoporotic women.3,4
The results of the Ipriflavone Multicenter European Fracture Study Group5 were recently published, and the data unfortunately indicate that ipriflavone does not prevent bone loss or affect biochemical markers of bone metabolism in postmenopausal women. This large, randomized, placebo-controlled, three-year study also demonstrated a significant decrease in lymphocyte concentrations (27%-33%) in women receiving ipriflavone. Although, this decrease was subclinical, the authors concluded that the risk-benefit ratio of this drug is not favorable compared to other antiresorptive therapies.5
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