The impact of plant-based diets on female bone mineral density Evidence based on seventeen studies

Background: An increase in awareness of plant-based diets has brought forth numerous studies on bone mineral density (BMD). The present systematic review and meta-analysis was designed to compare the effect between plant-based diets and omnivores on female BMD. Methods: We searched the Cochrane Library, PubMed, EMBASE, and Web of Science and up to July 1, 2020. Mean difference (MD) with its 95% confidence interval (CI) was estimated to compare the outcomes of the groups. We compared BMD at the lumbar spine, femoral neck and whole body respectively between plant-based diets and omnivores. In addition, we performed subgroup analyses according to different clinical characteristics for further exploration. Two reviewers assessed trial quality and extracted data independently. All statistical analyses were performed using standard statistical procedures provided in Review Manager 5.2. Results: A total of 17 cross-sectional studies including 13,888 patients were identified for the present meta-analysis. Our pooled result indicated that population with plant-based diets had lower BMD than omnivores at the lumbar spine (MD -0.03; 95% CI -0.04 to -0.02; P < .0001), femoral neck (MD -0.04; 95% CI -0.05 to -0.03; P < .00001) and whole body (MD -0.04; 95% CI -0.06 to -0.01; P = .01), respectively. Further exploration indicated that especially females with plant-based diets experienced significantly lower BMD at lumbar spine (MD -0.03; 95% CI -0.04 to -0.02; 3173 pts), femoral neck (MD -0.04; 95% CI -0.05 to -0.03; 10,656 pts) and whole body (MD -0.05; 95% CI -0.10 to -0.00; P = .04). In addition, we performed subgroup analyses and found lower BMD at lumbar spine and femoral neck in both vegetarians and vegans. Conclusions: The present meta-analysis indicated that plant-based diets may be correlated with lower BMD of women when compared with omnivore population. However, this does not diminish the fact that a plant-based diet can be a harmful option to the overall bone health of population and more prospective researches are needed to clear the impact of plant-based diets on bone health.