Supplementation with cod protein hydrolysate in older adults: a dose range cross-over study

A large proportion of older adults are affected by impaired glucose metabolism. Previous studies with fish protein have reported improved glucose regulation in healthy adults, but the evidence in older adults is limited. Therefore, we wanted to assess the effect of increasing doses of a cod protein hydrolysate (CPH) on postprandial glucose metabolism in older adults. The study was a double-blind cross-over trial. Participants received four different doses (10, 20, 30 or 40 mg/kg body weight (BW)) of CPH daily for 1 week with 1-week washout periods in between. The primary outcome was postprandial response in glucose metabolism, measured by samples of serum glucose and insulin in 20 min intervals for 120 min. The secondary outcome was postprandial response in plasma glucagon-like peptide 1 (GLP-1). Thirty-one subjects aged 60-78 years were included in the study. In a mixed-model statistical analysis, no differences in estimated maximum value of glucose, insulin or GLP-1 were observed when comparing the lowest dose of CPH (10 mg/kg BW) with the higher doses (20, 30 or 40 mg/kg BW). The estimated maximum value of glucose was on average 0·28 mmol/l lower when the participants were given 40 mg/kg BW CPH compared with 10 mg/kg BW (P = 0·13). The estimated maximum value of insulin was on average 5·14 mIU/l lower with 40 mg/kg BW of CPH compared with 10 mg/kg BW (P = 0·20). Our findings suggest that serum glucose and insulin levels tend to decrease with increasing amounts of CPH. Due to preliminary findings, the results require further investigation.