Effects of a casein hydrolysate versus intact casein on gastric emptying and amino acid responses

PurposeMilk proteins and/or their hydrolysates have been reported to have beneficial effects for improving postprandial glycaemia. Gastric emptying is a major determinant of postprandial glycaemia, yet limited studies have examined the effects of intact milk proteins compared to hydrolysates on gastric emptying. We investigated gastric emptying of a casein hydrolysate compared to intact casein.MethodsNine overweight and obese adults (meanSD age: 59.56.5years and BMI 28.4 +/- 2.6kg/m(2)) were studied in a randomised crossover design. Gastric emptying was assessed by paracetamol absorption test, with HPLC-MS being used for determining paracetamol and its primary metabolites in plasma. Glucose, insulin and amino acid responses were also assessed.ResultsLinear mixed model analysis showed no effect of treatment [F-(1,F- 55)=2.1, P=0.16] or treatmentxtime interactions [F-(6,F- 54)=1.5, P=0.21] for paracetamol concentrations. In addition, there were no significant differences between the intact casein and hydrolysate for any of the gastric emptying outcome measures (Cmax, AUC(0-30min), AUC(0-60min); AUC(0-240min)). However, insulin was increased in the early postprandial period (iAUC(0-15min,) iAUC(0-30min;)P<0.05) and there was a treatment effect for glucose [F-(1,F- 53)=5.3, P=0.03] following the casein hydrolysate compared to intact casein. No significant differences in amino acids were found between the two conditions.ConclusionsGastric emptying of a casein hydrolysate compared to intact casein does not differ. Mechanisms other than gastric emptying, for example the presence of a bioactive peptide sequence, may contribute to the glycaemic management effects of certain milk protein hydrolysates and warrant further investigation.