hydroxyproline

Amino-acid

What is it

Hydroxyproline is a non-essential amino acid found almost exclusively in collagen and elastin. It is produced in the body by the hydroxylation of proline using vitamin C and the enzyme prolyl hydroxylase.

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Collagen synthesis (as part of complete collagen peptides)

Good Evidence

Collagen peptide supplements (which contain hydroxyproline) have moderate evidence for improving skin elasticity and joint comfort. Isolated hydroxyproline has not been studied in the same way.

How it works

Hydroxyproline stabilizes the triple-helix structure of collagen by forming hydrogen bonds between adjacent strands. The body cannot incorporate dietary hydroxyproline directly into proteins; instead, it makes hydroxyproline 'on the fly' from proline residues already in collagen, using vitamin C as a cofactor. This is why severe vitamin C deficiency causes scurvy: without enough vitamin C, the body can't hydroxylate proline, collagen synthesis fails, and connective tissue breaks down. Supplemental hydroxyproline is taken up by cells and may serve as a signal for collagen synthesis through receptors such as PEPT1, though the practical benefit of isolated hydroxyproline over a complete collagen peptide is unclear.

Dosage

There is no RDA, AI, or UL specifically for hydroxyproline. Collagen peptide supplements typically deliver 2.5-15 g per day and contain naturally occurring hydroxyproline. Pure hydroxyproline supplementation is uncommon.

When and how to take it

If included in a collagen peptide product, take with or without food. Pairing with adequate vitamin C supports endogenous collagen synthesis.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Hydroxyproline within collagen peptides

The form most consumers actually encounter.

Released during digestion of collagen peptides; small di- and tripeptides containing hydroxyproline are absorbed intact.

Free L-hydroxyproline

Rare as a standalone supplement.

Absorbed via amino acid transporters.

Safety

Generally well tolerated. Few studies of isolated hydroxyproline have reported safety problems.

Who should be cautious

People with kidney disease who must restrict total protein intake should account for amino acid supplements. Pregnant and breastfeeding women should rely on dietary collagen sources rather than isolated supplements unless advised by a clinician.

Interactions

No significant interactions reported.

Food sources

Bone broth

Amount
1 cup (240 mL)
%DV
—

Gelatin

Amount
1 tbsp (~7 g)
%DV
—

Skin and connective tissue of meat and fish

Amount
3 oz (~85 g)
%DV
—

Frequently asked questions

Is hydroxyproline the same as collagen?⌄

No. Hydroxyproline is one of the amino acids that make up collagen. It is a marker of collagen content in tissue but is just a single building block, not the whole protein.

Will hydroxyproline give me younger-looking skin?⌄

On its own, probably not. Most skin studies use collagen peptides, which contain hydroxyproline along with proline, glycine, and many other amino acids. Adequate vitamin C is more important for endogenous collagen synthesis than supplemental hydroxyproline.

References

hydroxyproline on Wikidata — Wikidata link

hydroxyproline (ChEBI:18095) — ChEBI link

hydroxyproline (PubChem CID 5810) — PubChem link

hydroxyproline on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on hydroxyproline (PubMed search) — PubMed link

Track hydroxyproline with Pilora

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.