Comparison of gelatin and low-molecular weight gelatin hydrolysate ingestion on hydroxyproline (Hyp), Pro-Hyp and Hyp-Gly concentrations in human blood

This study showed that gelatin ingestion significantly increased prolyl-hydroxyproline (Pro-Hyp) levels in plasma of 9 subjects, with maximum concentrations of 15.5 ± 3.0 nmol/mL 2 h post-ingestion. Hydroxyprolyl-glycine (Hyp-Gly) concentrations were significantly increased and reached a maximal level of 2.3 ± 0.5 nmol/mL 1 h post-ingestion of gelatin. A low molecular weight gelatin hydrolysate (LMW-GH) significantly enhanced concentrations of both peptides, while gelatin hydrolysate ingestion did not significantly enhance the maximum concentration and area under the plasma concentration-time curve (AUC) of Hyp-Gly relative to gelatin. The absorption of free Hyp following gelatin ingestion (94.4 ± 16.4 nmol/mL) was significantly lower relative to GH (150.9 ± 15.3 nmol/mL) and LMW-GH (169.1 ± 32.5 nmol/mL). The present study is the first report demonstrating that Hyp-containing peptides are elevated to μM levels in human plasma after gelatin ingestion. These results suggested that gelatin is useful as a functional food as effectively as GH.