Persistent Effects of a Soy Diet in Early Development on Bone in Female Rats

Abstract

We have previously reported that feeding soy protein isolate (SPI) diet to pre‐pubertal animals had a beneficial effect on bone accretion. However, it currently remains unclear whether the positive effects of SPI diet on bone in early life will persist to adulthood. In the present study, we fed postnatal day (PND) 24 weanling female rats with SPI diet for 30 days, and on PND 55 we switched SPI diet to a control casein diet until 6 months of age. At age 6 months, rats either underwent ovariectomy (OVX) or sham operation, and thereafter continued on control or SPI‐diets for 1 or 3 weeks. Using peripheral quantitative CT scanning, we demonstrated that total bone mineral content and trabecular bone mineral density (BMD) were significantly increased in 30‐day SPI‐fed rats compared to their controls (p < 0.05). Both long‐term (continuous) SPI (LT‐SPI) and short term (early life only) SPI (ST‐SPI) diet protected against one week of OVX‐associated bone loss. On the other hand, LT‐SPI diet protected loss of total, trabecular and cortical BMD three weeks after OVX, whereas ST‐SPI diet only protected against cortical BMD loss (p < 0.05). These results suggest that ST‐SPI diet has modest protective effects against sex‐steroid deficiency‐induced bone loss in adult females. Supported in part by ARS CRIS #6251–51000‐005–03S.