Abstract
Abstract Background and Objective There has been a resurgence of interest in the controversial relationship between dietary protein and bone health. This paper reports the first systematic review and meta-analysis of the relationship between protein and bone health in healthy human adults. Data sources/Methods The MEDLINE® (January 1966 to September 2007) and EMBASE (1974- July 2008) databases were electronically searched for all relevant studies of healthy adults, excluding studies examining calcium excretion or calcium balance. Results In cross sectional surveys, all pooled r values for the relationship between protein intake and BMD/BMC at the main clinically relevant sites were significant and positive, with protein intake explaining 1-2% of BMD. A meta-analysis of randomised, placebo controlled trials indicated a significant positive influence of all protein supplementation on lumbar spine BMD, but showed no association with relative risk (RR) of hip fractures. No significant effects were identified for soy protein or milk basic protein (MBP) on lumbar spine BMD. Conclusion A small positive effect of protein supplementation on lumbar spine BMD in randomised placebo controlled trials supports the positive association between protein intake and bone health found in cross sectional surveys. However, these results were not supported by cohort study findings for hip fracture risk. Any effects found were very small and had 95% confidence intervals which were close to zero. Therefore there is a small benefit of protein on bone health found here but any benefit may not necessarily translate into reduced fracture risk in the long term.