Changes in composition and content of food-derived peptide in human blood after daily ingestion of collagen hydrolysate for 4 weeks

Shigemura Y, Suzuki A, Kurokawa M, Sato Y, Sato K · Journal of the Science of Food and Agriculture

The one study of what daily dosing does to the peptides themselves. Hydroxyproline peptides peak about an hour after a dose and return to baseline within 24 hours, so nothing accumulates between doses. Over four weeks the mix shifted: the proportion of Hyp-Gly tended to rise while Pro-Hyp tended to fall, though Pro-Hyp remained the dominant species throughout. Seven other Hyp peptides were identified, including Pro-Hyp-Gly, Ile-Hyp, Leu-Hyp, Glu-Hyp and Ala-Hyp.

Population

Human volunteers taking collagen hydrolysate daily

Intervention

4.5 g/day collagen hydrolysate for 4 weeks, with blood peptide profiling

Limitations

No control group, no group size in the abstract, and no biological endpoint — this measures peptides, not effects. The proposed explanation, that daily intake alters gut protease activity, is the authors' speculation and was not tested. 4.5 g/day is well below the doses used in the joint trials.