Phytoestrogens as hormone replacement therapy: an evidence-based approach

Postmenopausal women have sought nonestrogen alternatives to hormone replacement in order to avoid possible risks and side effects of the therapy. Selective estrogen receptor modulators have been developed to tailor therapy to a specific risk/benefit profile that will best fit the patient. More women have looked to phytoestrogens, such as the isoflavones found in the soy plant, to tailor their menopausal therapy in a "natural" way. This review examines the evidence regarding the risks and benefits of isoflavones as hormone replacement therapy. Controlled trials have shown a reduction in postmenopausal hot flashes when subjects' diets were supplemented with soy. There is less evidence for a benefit in vaginal dryness symptoms. Furthermore, dietary supplementation also appears to lower total and low-density lipoprotein cholesterol in hypercholesterolemic subjects. A synthetic isoflavone, ipriflavone, has been shown in controlled trials to prevent postmenopausal bone loss, though there is much less evidence that soy isoflavones will accomplish this goal. Finally, although unopposed estrogen replacement may promote breast and endometrial cancer, there is no evidence that phytoestrogens will do the same. In contrast, great interest has been taken in the potential cancer-protective effects of phytoestrogens, though prospective evidence in postmenopausal women is not available. Although data regarding the use of isoflavone extracts are incomplete, dietary supplementation with soy foods appears to be a safe and possibly beneficial option for postmenopausal women.