Objective: This study was undertaken to evaluate the effects of varying doses of phytoestrogens on lipid and bone metabolism in postmenopausal women.
Design: A novel red clover isoflavone preparation (Rimostil) containing genistein, daidzein, formononetin, and biochanin was administered to 46 postmenopausal women in a double-blind protocol after a single-blind placebo phase and followed by a single-blind washout phase. Patients were randomized to receive either 28.5 mg, 57 mg, or 85.5 mg of phytoestrogens daily for a 6-month period.
Results: At 6 months, the serum high-density lipoprotein cholesterol had risen significantly by 15.7-28.6% with different doses (p = 0.007, p = 0.002, p = 0.027), although the magnitude of the response was independent of the dose used. The serum apolipoprotein B fell significantly by 11.5-17.0% with different doses (p = 0.005, p = 0.043, p = 0.007) and the magnitude of the response was independent of the dose used. The bone mineral density of the proximal radius and ulna rose significantly by 4.1% over 6 months with 57 mg/day (p = 0.002) and by 3.0% with 85.5 mg/day (p = 0.023) of isoflavones. The response with 28.5 mg/day of isoflavones was not significant. There was no significant increase in endometrial thickness with any of the doses of isoflavone used.
Conclusion: These results show that the administration of an isoflavone combination extracted from red clover was associated with a significant increase in high-density lipoprotein cholesterol, a significant fall in apolipoprotein B, and a significant increase in the predominantly cortical bone of the proximal radius and ulna after 6 months of treatment. Interpretation of the results is undertaken cautiously because of the absence of a simultaneously studied control group.