Objective This study was conducted to assess the effect of hydrolysis level of collagen on its absorption.
Methods An open-label, three-treatment cross over study was conducted in 7 healthy adult volunteers. All subjects received the following 3 types of porcine skin collagen test meals at the same dose（1.3 g）of hydroxyproline（Hyp）：drink containing collagen hydrolysates（average molecular weight of 2500）, gelatin powder, and porcine skin snack. Sequential plasma samples were collected up to 3 hours after ingestion, and measured plasma concentration of total, free, and peptide form Hyp.
Results The plasma concentrations of Hyp were elevated in all groups. However, the significant differences were observed in the plasma concentrations and the area under the plasma concentration curves（AUCs）among the groups. The plasma concentration of total Hyp was elevated and reached the maximum concentration the fastest after the collagen hydrolysates ingestion. The AUC_0-3h of total, free, and peptide form Hyp of the collagen hydrolysate and gelatin group were significantly higher than that of the porcine skin snack group, and AUC_0-1h of total and free Hyp of the collagen hydrolysate group was significantly higher than that of the other groups. Furthermore, the ratio of peptide form Hyp to total Hyp tended to be high in order of the collagen hydrolysate, gelatin, porcine skin snack.
Conclusion We concluded that collagen absorption depends on the hydrolysis level of it and that collagen hydrolysates are absorbed more rapidly than gelatin and conventional foods.