Osteoporosis Home > Phytoestrogens
Much of the evidence concerning the potential role of phytoestrogens in bone health is based on animal studies. In fact, soybean protein, soy isoflavones, genistein, daidzein, and coumestrol have all been shown to have a protective effect on bone in animals whose ovaries had been surgically removed.
In humans, however, the evidence is conflicting. Studies show that compared to Caucasian populations, those in Hong Kong, China, and Japan -- where dietary phytoestrogen intakes are high -- experience lower rates of hip fracture. Yet, according to the Surgeon General's Report on Bone Health and Osteoporosis, spine fractures are almost as common in Asian women as they are in white women. In addition, reports suggest that Japanese women have a greater risk of sustaining a vertebral fracture than Caucasian women.
Several studies have explored the effects of soy isoflavones on bone health, but these results have been mixed, ranging from a modest impact to no effect. Most of these studies have serious limitations, including their short duration and small sample size, making it difficult to fully evaluate the impact of these compounds on bone health.
Ipriflavone, a synthetic isoflavone, has shown some promise in its ability to preserve bone in postmenopausal women. Ipriflavone has also been shown to have a protective effect on bone density in premenopausal women taking the treatment called GnRH (gonadotropin-releasing hormone), which is for endometriosis. One of the side effects of this treatment is bone loss.
However, a definitive three-year study of more than 400 postmenopausal women concluded that ipriflavone did not prevent bone loss. In addition, the compound was linked to lymphocytopenia (a reduction in lymphocytes) in a significant number of study participants. Lymphocytes are a type of white blood cell that helps the body fight infection.