Last verified: 17 days ago
L-Hydroxyproline
Also known as: Hydroxy-L-proline, HYP, trans-4-hydroxy-L-proline, N-acetyl-L-hydroxyproline, NAHP
Evidence under review. — Not yet rated
Amino acid found in collagen. Limited human evidence; mostly used as a lab marker for collagen and fibrosis.
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What it does
L-Hydroxyproline is an amino acid that makes up a significant portion of collagen, the structural protein in skin, cartilage, and connective tissue. In research settings, it is primarily used as a...
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Evidence quality
Evidence base hasn't been formally rated yet. See research below.
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Clinical dose
No established dose
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Found in
What the Science Says
L-Hydroxyproline is an amino acid that makes up a significant portion of collagen, the structural protein in skin, cartilage, and connective tissue. In research settings, it is primarily used as a biomarker to measure collagen content and tissue fibrosis rather than as a standalone supplement. A derivative called N-acetyl-L-hydroxyproline (NAHP) has shown in lab and tissue studies that it may inhibit the formation of advanced glycation end-products (AGEs), which are linked to skin aging and stiffening. No established oral dosing for humans exists from the provided studies.
What It Doesn't Do
Not proven to directly build collagen when taken as a supplement. No human clinical trials show it improves joint pain, skin appearance, or athletic recovery on its own. Don't confuse it with collagen peptides — they are not the same thing. No evidence it treats kidney disease or prevents kidney stones in humans.
Evidence-Based Benefits
A derivative (NAHP) reduced AGE formation in lab and skin tissue models, which may help prevent skin stiffening and yellowing.
Weak EvidenceEffective at: No established dose
Supporting studies (click to view on PubMed):
HYP analogs reduced calcium oxalate crystal formation in a fruit fly model of primary hyperoxaluria.
Weak EvidenceEffective at: No established dose
Supporting studies (click to view on PubMed):
Absorption & Bioavailability
Unknown — no human pharmacokinetic or absorption data in the provided studies
Red Flags to Watch For
- No human clinical trials support oral L-hydroxyproline supplementation for any health outcome based on the provided evidence
- Most research uses it as a laboratory measurement tool, not a therapeutic ingredient — marketing it as a supplement may be misleading
- 127 registered supplement products contain it despite a near-total absence of human efficacy data
- Animal and in vitro studies cannot be directly extrapolated to human supplement use
Products Containing L-Hydroxyproline
See how L-Hydroxyproline is used in these analyzed products:
Frequently Asked Questions
What does L-Hydroxyproline do?
Amino acid found in collagen. Limited human evidence; mostly used as a lab marker for collagen and fibrosis.
What is the effective dose of L-Hydroxyproline?
No established dose
Is L-Hydroxyproline safe?
No human clinical trials support oral L-hydroxyproline supplementation for any health outcome based on the provided evidence
What doesn't L-Hydroxyproline do?
Not proven to directly build collagen when taken as a supplement.
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-05-25