Hydroxyproline is a non-standard amino acid produced in the body when the enzyme prolyl hydroxylase converts proline to hydroxyproline inside collagen fibers — a process that requires vitamin C as a cofactor. It makes up roughly 13–14% of all the amino acids in collagen, making it one of the most abundant amino acids in the human body overall. Because it is so uniquely concentrated in collagen, measuring hydroxyproline in urine or tissue is actually used clinically as a marker of collagen turnover.

Hydroxyproline stabilizes the triple-helix structure of collagen by forming hydrogen bonds between the collagen chains, giving connective tissue its tensile strength. When you consume collagen-rich foods or supplements, hydroxyproline-containing peptides are absorbed from the gut and travel to tissues like skin, cartilage, and bone, where they signal fibroblasts and chondrocytes to ramp up their own collagen production. This dual role — as a building block and as a signaling molecule — is what makes it especially useful for supporting tissue repair.

Hydroxyproline is not commonly sold as an isolated amino acid supplement. Most people get it through collagen hydrolysate powders, collagen peptide capsules, gelatin, or bone broth concentrates. Some clinical research uses purified collagen tripeptides or standardized collagen hydrolysates with a known hydroxyproline content. Isolated hydroxyproline powder exists for research use but is rarely seen in consumer products.

• Joint pain and stiffness
• Osteoarthritis
• Skin aging and loss of elasticity
• Wound healing and tissue repair
• Bone density and osteoporosis
• Muscle recovery after exercise
• Tendon and ligament injuries
• Gut lining support (leaky gut)

• Progressive cartilage degradation in early joint disease
• Age-related bone loss (when combined with calcium and vitamin D)

• Bone broth — Made by slow-simmering animal bones and connective tissue, bone broth is one of the richest dietary sources of hydroxyproline-containing collagen peptides available in a whole-food form.
• Pork skin / pork rinds — Pork skin is extremely high in collagen and delivers a concentrated dose of hydroxyproline; it has one of the highest collagen contents of any commonly eaten food.
• Chicken skin and cartilage — Chicken collagen, especially from the skin and cartilage around joints, provides a meaningful amount of hydroxyproline and is the basis of several clinical collagen supplements.
• Gelatin (collagen cooked form) — Gelatin is denatured collagen and contains roughly the same amino acid profile as collagen, including 13–14% hydroxyproline by mass — making it one of the simplest ways to get this amino acid from food.
• Sardines and salmon with skin — Fish skin and the soft bones of small fish like sardines are good marine sources of collagen and hydroxyproline, and marine collagen peptides are increasingly used in clinical studies.

• Mild bloating or digestive discomfort (especially at doses above 15g/day)
• Nausea if taken on an empty stomach at high doses
• Unpleasant taste or texture (specific to some collagen powder products)
• Rare allergic reactions in people with fish or shellfish allergies when using marine collagen sources

• Recommended daily: 10–15g of collagen hydrolysate daily (providing approximately 1.3–2g of hydroxyproline); isolated hydroxyproline studies have used 2–5g per day
• Best time of day: Morning or 30–60 minutes before exercise; some evidence suggests pre-workout timing enhances collagen synthesis in tendons and ligaments
• With or without food: Can be taken with or without food; taking with a vitamin C source (such as a small glass of orange juice or a citrus-based drink) significantly enhances collagen synthesis
• Time to effect: 4–8 weeks for skin benefits; 8–12 weeks for joint and bone outcomes
• How long to take it: Daily use for a minimum of 3 months is recommended to assess full benefit; long-term daily use appears safe based on available data. No cycling protocol is required.