Effects of Dietary Intake of Isoflavone Aglycone-rich Fermented Soybeans on Bone Metabolism in Ovariectomized Rats

We compared the effect of dietary intake of isoflavone aglycone-rich fermented soybeans (FS) with that of glucoside-rich non-fermented soybeans (NFS) on bone metabolism, using ovariectomized (OVX) rats. Female Sprague-Dawley rats were given OVX or a sham operation at 8 weeks of age. After a 2-week recovery, shamoperated rats were given a NFS diet for 57 days, while OVX rats were given the NFS or FS diet (Sham-NFS, OVX-NFS, and OVX-FS group, n = 10). The two diets had the same level of total isoflavone (228µmol/100 g). The percentage of isoflavone aglycone to total isoflavone was 100% in the FS diet, and approximately 5% in the NF Sd iet. Tibial bone calcium and phosphorus contents were significantly lower in the OVX-NFS group than in the Sham-NFS group. This reduction was significantly prevented in the OVX-FS group. Tibial trabecular bone density was also significantly reduced by OVX, but the reduction tended to be prevented in the OVX-FS group (p =0 .1). The level of urinary deoxypyridinoline (DPD), a bone resorption marker, was significantly increased by OVX; this increase was significantly prevented in the OVX-FS group. Moreover, urinary total isoflavone levels tended to be higher in the OVX-FS group than in the OVX-NFS group (p =0 .1). In conclusion, this study suggested that intake of FS prevented excessive bone resorption and bone loss following OVX in rats. It was also suggested that these beneficial effects on bone resulted from higher absorption of isoflavone aglycone.