Differences of digestive kinetics of whey and casein are not linked to satiety and gastrointestinal hormone secretions in humans

Abstract

To verify whether digestion kinetics influence the satiating effect of proteins, we measured digestive kinetics, hormonal secretions and satiety in humans after the ingestion of caseins or whey proteins. Satiety was studied in 37 overweight subjects. On the 1st day, they received a control liquid snack containing 60 g of carbohydrates. Satiety scores and the delay between the snack and the spontaneous demand for lunch were recorded. Subjects were then adapted to consume daily a protein liquid snack containing 30 g of carbohydrates and 30 g of caseins (n=18) or whey proteins (n=19) for 7 days. A 2nd satiety test was realized after the ingestion of the protein snack. Two days later, 15 of the subjects were equipped with a jejunal tube and a venous catheter. Digestive kinetics and plasma hormone concentrations were studied after the ingestion of their snack meal. Compared to the control snack, proteins tended to increase the delay between the snack and the lunch (+ 13±13min, p=0.06), without any difference between groups. The protein snack did not elicit significant secretion of PYY, GLP1 and glucagon from the baseline. Whey proteins were totally delivered to the intestine within 2 h after the meal whereas 5 h were required for caseins. Important modulations in digestive kinetics of dietary protein do not translate into satiety signals or intestinal hormone production in overweight subjects adapted to their protein snack.