ANIMAL VERSUS PLANT PROTEIN INTAKE AND BONE HEALTH‐A SYSTEMATIC REVIEW AND META‐ANALYSIS OF RANDOMIZED CONTROLLED TRIALS
Authors: Shams‐White Marissa M. M. , Fu Zhuxuan , Karlsen Micaela , Sackey Joachim , Shi Jian , Insogna Karl , LeBoff Meryl , Shapses Sue , Weaver Connie , Wallace Taylor , Chung Mei 
Published: November 2023

ObjectiveTo conduct a systematic review and meta‐analysis evaluating the effects of animal versus plant protein intake on bone mineral density (BMD), bone mineral content (BMC) and select bone biomarkers in healthy adults. [Registered on International Prospective Register of Systematic Reviews: PROSPERO CRD42015017751].MethodsThis study is a sub‐analysis of a larger systematic review following the methodologies in the Cochrane handbook. Searches across five databases were conducted through June 21, 2016 for randomized controlled trials (RCTs) in healthy adults that examined the effects of animal versus plant protein intake on 1) total body (TB), total hip (TH), lumbar spine (LS) or femoral neck (FN) BMD or TB BMC for at least one year, or 2) select bone formation and resorption biomarkers for at least six months. Random effect meta‐analyses were performed using Stata when data are sufficient.ResultsSeven RCTs were included in qualitative and quantitative synthesis. All included studies were parallel RCTs in healthy peri‐menopausal (n=1 study) and post‐menopausal (n=6) women. All plant protein sources were soy protein; animal protein sources were from milk (n=5), egg white (n=1) or not stated (n=1). Protein interventions ranged from 18–40g. There were no significant differences in BMD or BMC outcomes across studies between soy and animal protein groups, nor when examining collagen type‐1 cross‐linked N‐telopeptide (NTX, n=4)) or deoxypyridinoline (n=1). Though one study found soy protein significantly decreased collagen type‐1 cross‐linked C‐telopeptide (CTx) and bone‐specific alkaline phosphatase (BSAP) compared to milk protein, there were no further studies examining CTx, and BSAP did not significantly differ between groups in other studies (n=4).Meta‐analysis results showed on average, the difference between groups were close to zero and not significant for BMD outcomes (LS: n=4, WMD: 0.001 g/cm2, 95% CI: CI −0.006, 0.009, I2: 2.6%; TB: n=3, WMD: 0.001 g/cm2, 95% CI: −0.005, 0.007, I2: 0.0%; FN: n=3, WMD: −0.000 g/cm2, 95% CI: −0.006, 0.005, I2: 0.0%) and NTx (N=3, WMD: 0.644 nmol BCE, 95% CI −3.004, 4.293, I2: 0.0%;), and there was a nonsignificant, small effect size for BSAP (n=3, SMD: −0.06, 95% CI −0.29, 0.18, I2=0.0%). All outcomes had wide confidence intervals and no to low statistical heterogeneity. While overall risk of bias was low, half of the studies provided inadequate randomization information and had <80% compliance.ConclusionsResults suggest there is no significant difference between plant and animal protein's effects on bone health outcomes in post‐menopausal women. However, studies were limited in number and findings among post‐menopausal women may not be generalizable to other populations. Future studies are needed examining the effects of different protein sources in different populations on BMD, BMC and biomarker outcomes.Support or Funding InformationFunding source: National Osteoporosis Foundation