Phytoestrogens (PEs) are naturally occurring plant polyphenols with oestrogenic activity. Soy protein-free diet excludes alfalfa and soybean meal, minimising PE content. This study evaluated long-term effects of 2056 Soy Protein-Free (SF) diet on bone turnover, mass and strength over 18 months (M) in aged OVX Mauritius monkeys. Animals fed SF diet were compared with historical data1 obtained from animals fed standard diet (SD). Compared with sham, biomarkers for OVX animals showed greater increases in those fed SF diet relative to SD. At 6 and 18M: on SF diet, osteocalcin increased 19% and 22%, serum CTx 16% and 12%, Bone-ALP 58% and 62%, relative to SD. Greater increases in biomarkers were associated with more consistent and greater decreases in bone mass. Relative to sham at 6 and 18 M, for animals fed SF diet, DXA BMD decreased 9% and 10% at lumbar spine and 8.7% and 9% at proximal femur, respectively. At 18 M, animals fed SD showed decreases of 4.8% at lumbar spine and 5.2% at proximal femur. On SF diet tibia trabecular pQCT BMD decreases were 16.5% and 24% at 6 and 18M, with decreases in cortical BMD at the tibial diaphysis of 5.4% and 5.3%. These decreases were more marked at 18 M compared with SD animals, which showed decreases of 11% for trabecular BMD and 3.7% for cortical BMD. Bone strength parameters were similar for animals on either diet. These data suggest dietary PEs may influence the OVX response in aged monkeys as evidenced by greater increases in bone turnover and loss of bone mass on SF diet allowing better discrimination when evaluating potential anti-osteoporosis drugs.
Disclosure: The authors declared no competing interests.
1. Smith SY et al, (2009) AJP.