Dietary Protein Intake above the Current RDA and Bone Health: A Systematic Review and Meta-Analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials and prospective cohort studies.
PubMed 28686536 · doi:10.1080/07315724.2017.1322924
What was done
Systematic review and meta-analysis conducted following PRISMA guidelines across PubMed, Ovid Medline, and Agricola through April 2017. The review evaluated randomized controlled trials and prospective cohort studies in healthy adults aged 18 and older examining dietary protein intake at or above the current RDA (0.8 g/kg/day or 10% to 15% of total energy) from any source on fractures, bone mineral density, bone mineral content, and bone turnover markers. A total of 29 articles were included, comprising 16 randomized controlled trials and 13 prospective cohort studies.
What was found
Meta-analysis of prospective cohort studies showed that high versus low protein intake resulted in a statistically significant 16% decrease in hip fractures (standardized mean difference = 0.84, 95% CI, 0.73 to 0.95; I2 = 36.8%). Studies collectively indicated that protein intake above the RDA had a beneficial effect on bone mineral density across several sites. No differences were observed between plant and animal protein sources.
Why it matters
This synthesis provides evidence that dietary protein intake exceeding standard recommended dietary allowances supports bone maintenance and reduces hip fracture risk, addressing historical concerns regarding potential adverse skeletal effects of higher protein consumption.
Limits
The hip fracture outcome is based on observational prospective cohort studies rather than randomized trials. Numerical effect sizes and confidence intervals for bone mineral density and bone turnover markers are not detailed in the abstract. Comparative data on plant versus animal protein sources were scarce, and trials in women not using hormone replacement therapy were noted as an ongoing need.
Cited by
- supports There is no scientific evidence that high protein intakes cause kidney damage or reduce bone density in healthy individuals.