The skeletal safety of milk-derived proteins: A meta-analysis of randomized controlled trials

Purpose There has been a persistent claim that dairy products contain calcium-leaching proteins, although the soundness of such a claim has been challenged. A meta-analysis of randomized controlled trials (RCTs) on the effects of milk-derived protein supplementation on bone health indices in adults was performed to reconcile the controversy surrounding the potential skeletal safety concerns of proteins of dairy origin. Methods The PubMed and Web of Science databases were searched for relevant RCTs. A random-effects model was used to generate pooled effect sizes and 95% confidence intervals. Results Milk-derived protein supplementation did not significantly affect whole-body BMD ( n = 7 RCTs) and BMD at the lumbar spine ( n = 10), hip ( n = 8), femoral neck ( n = 9), trochanter ( n = 5), intertrochanter ( n = 2), and ultradistal radius ( n = 2). The concentrations of bone formation markers (bone-specific alkaline phosphatase [ n = 11], osteocalcin [ n = 6], procollagen type 1 amino-terminal propeptide [ n = 5]), bone resorption markers (N-terminal telopeptide of type 1 collagen [ n = 7], C-terminal telopeptide of type 1 collagen [ n = 7], deoxypyridinoline [ n = 4]), and parathyroid hormone ( n = 7) were not significantly affected. However, increased insulin-like growth factor-1 (IGF-1) concentrations ( n = 13) were observed. Reduced IGF-1 concentrations were observed when soy protein was used as a comparator, and increased IGF-1 concentrations were observed when carbohydrate was used. Conclusion Our findings do not support the claim that proteins of dairy origin are detrimental to bone health.