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.European Journal of Clinical Nutrition advance online publication, 22 August 2007; doi:10.1038/sj.ejcn.1602891.