Dietary protein and bone health across the life-course: an updated systematic review and meta-analysis over 40 years.

We undertook a systematic review and meta-analysis of published papers assessing dietary protein and bone health. We found little benefit of increasing protein intake for bone health in healthy adults but no indication of any detrimental effect, at least within the protein intakes of the populations studied. This systematic review and meta-analysis analysed the relationship between dietary protein and bone health across the life-course. The PubMed database was searched for all relevant human studies from the 1st January 1976 to 22nd January 2016, including all bone outcomes except calcium metabolism. The searches identified 127 papers for inclusion, including 74 correlational studies, 23 fracture or osteoporosis risk studies and 30 supplementation trials. Protein intake accounted for 0-4% of areal BMC and areal BMD variance in adults and 0-14% of areal BMC variance in children and adolescents. However, when confounder adjusted (5 studies) adult lumbar spine and femoral neck BMD associations were not statistically significant. There was no association between protein intake and relative risk (RR) of osteoporotic fractures for total (RR(random) = 0.94; 0.72 to 1.23, I2 = 32%), animal (RR (random) = 0.98; 0.76 to 1.27, I2 = 46%) or vegetable protein (RR (fixed) = 0.97 (0.89 to 1.09, I2 = 15%). In total protein supplementation studies, pooled effect sizes were not statistically significant for LSBMD (total n = 255, MD(fixed) = 0.04 g/cm2 (0.00 to 0.08, P = 0.07), I2 = 0%) or FNBMD (total n = 435, MD(random) = 0.01 g/cm2 (-0.03 to 0.05, P = 0.59), I2 = 68%). There appears to be little benefit of increasing protein intake for bone health in healthy adults but there is also clearly no indication of any detrimental effect, at least within the protein intakes of the populations studied (around 0.8-1.3 g/Kg/day). More studies are urgently required on the association between protein intake and bone health in children and adolescents.

Protein hydrolysate co-ingestion does not modulate 24 h glycemic control in long-standing type 2 diabetes patients.

OBJECTIVE: Evaluate the efficacy of protein hydrolysate co-ingestion as a dietary strategy to improve blood glucose homeostasis under free-living conditions in long-standing type 2 diabetes patients. METHODS: A total of 13 type 2 diabetes patients were enrolled in a randomized, double-blind cross-over design and studied on two occasions for 40 h under strict dietary standardization but otherwise normal, free-living conditions. In one trial, subjects ingested a protein hydrolysate (0.4 g kg(-1) bw casein hydrolysate, PRO) with every main meal. In the other trial, a placebo was ingested (PLA). Blood glucose concentrations were assessed by continuous glucose monitoring. RESULTS: Average 24 h glucose concentrations were similar between the PLA and the PRO trials (8.9 +/- 0.8 vs 9.2 +/- 0.7 mmol l(-1), respectively). Hyperglycemia (glucose concentrations >10 mmol l(-1)) was experienced 34 +/- 9% of the time (8 +/- 2 h per 24 h) in the PLA trial. Protein hydrolysate co-ingestion with each main meal (PRO) did not reduce the prevalence of hyperglycemia (39 +/- 10%, 9 +/- 2 h per 24 h; P=0.2). CONCLUSION: Co-ingestion of a protein hydrolysate with each main meal does not improve glucose homeostasis over a 24 h period in long-standing type 2 diabetes patients.