L-Hydroxyproline
Also known as: Hydroxy-L-proline, HYP, trans-4-hydroxy-L-proline, N-acetyl-L-hydroxyproline, NAHP
Effective Dosage
No established dose
What the Science Says
L-Hydroxyproline is an amino acid that makes up a significant portion of collagen, the structural protein found in skin, cartilage, and connective tissue. In research settings, it is primarily used as a biomarker to measure collagen content in tissues — elevated levels often signal fibrosis or tissue damage, while its presence in supplements is marketed for skin and joint support. A derivative form, N-acetyl-L-hydroxyproline (NAHP), has shown in lab and tissue studies that it may reduce the formation of advanced glycation end-products (AGEs), which are compounds linked to skin aging and stiffening. No human clinical trials from the provided studies establish an effective dose or confirm benefits when taken orally as a supplement.
What It Doesn't Do
Not proven to rebuild cartilage or joints in humans. No clinical evidence it reduces wrinkles or reverses skin aging when taken as a pill. The AGE-blocking effects were shown in lab dishes and skin biopsies, not in people taking it orally. Don't confuse it with collagen peptides — they are not the same thing. No evidence it treats kidney stones or viral infections in humans.
Evidence-Based Benefits
L-Hydroxyproline is an amino acid that is a major component of collagen. Some studies suggest it may support joint health and tissue repair, but the evidence is limited and not robust.
Weak EvidenceEffective at: No established dose
Source: auto-research
Absorption & Bioavailability
Unknown — no human pharmacokinetic or absorption data in the provided studies. Oral bioavailability of free amino acids like hydroxyproline is generally considered moderate, but this is not confirmed by the provided research.
Red Flags to Watch For
- No human clinical trials in the provided evidence base support supplementation benefits
- Often used as a tissue damage marker in animal studies — elevated L-hydroxyproline in organs signals fibrosis, not health
- 127 registered supplement products exist despite a near-complete absence of human efficacy data
- Derivative forms (e.g., NAHP) tested in labs are not the same as plain L-hydroxyproline sold in supplements — marketing may conflate them
- Animal and in vitro findings (Drosophila, rat models, cell cultures) cannot be directly applied to human supplementation
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: 2026-04-06