Phytoestrogens are candidate drugs for the treatment of
osteoporosis. Many experiments have been designed to investigate the preventive effects of
phytoestrogens for
osteoporosis; however, it is easy for a single dissenting result from animal experiments to mislead clinical investigations. Herein, we use meta-analysis to assess the evidence for a protective effect of
phytoestrogens on ovariectomized rat models of
osteopenia. With respect to
osteoporosis, PubMed and Web of Science were searched from January 2000 to March 2013 for relevant studies of
phytoestrogens in ovariectomized rats. Two reviewers independently selected and assessed the studies. Data were aggregated using a random effects model. Meta-analysis revealed that the
phytoestrogen treatment group demonstrated a significantly higher femur bone mineral density and trabecular bone and lower bone turnover
markers (serum alkaline phosphatase and serum
osteocalcin) compared with the control ovariectomized group, thus showing a bone protective effect of
phytoestrogens in ovariectomized rats. Subsequent sensitivity analyses indicated that the effect of
phytoestrogens on serum
alkaline phosphatase and serum
osteocalcin are not robust. Despite the high heterogeneity in the systematic review of animal experiments, the present results indicated that
phytoestrogens may offer the most potential for the prevention of bone loss by reducing the expected loss of trabecular bone and bone mineral density. Their effects are likely due to inhibition of
bone resorption, but their benefits on bone formation are still unclear. Further studies are needed to assess the effect of
phytoestrogens on bone formation and the efficacy and safety of individual
phytoestrogens.