Proline is a non-essential amino acid — meaning your body can produce it, but many people don't make or get enough to meet demands during injury, aging, or high physical stress. It is uniquely structured compared to other amino acids, forming a ring shape that gives collagen its tight, coiled stability. Without adequate proline, collagen production slows and connective tissue integrity suffers.

Proline is one of the two key amino acids (alongside hydroxyproline) that make up roughly 25% of all collagen. Your body incorporates proline directly into collagen strands, and then converts some of it to hydroxyproline — a step that requires vitamin C. This gives collagen its triple-helix structure, the tight coil that makes tendons, skin, and cartilage strong and elastic. Proline also plays a supporting role in wound healing by stimulating fibroblasts, the cells that lay down new tissue.

Available as standalone L-Proline powder or capsules, or obtained indirectly through hydrolyzed collagen peptide supplements. Powder form allows flexible dosing and is often combined with vitamin C for enhanced collagen synthesis. Collagen peptides (types I, II, III) provide proline alongside hydroxyproline and glycine in a pre-digested, highly absorbable form.

• Skin aging and loss of firmness
• Joint pain and cartilage wear
• Wound healing and tissue repair
• Leaky gut and intestinal lining
• Tendon and ligament injuries
• Post-surgical recovery
• Stretch marks and skin damage
• Exercise-related connective tissue stress
• Bone density support

• Age-related collagen loss (when supplemented consistently alongside vitamin C and glycine)
• Exercise-induced tendon and ligament breakdown with strategic pre-exercise dosing
• Delayed or impaired wound healing in nutritionally depleted individuals

• Bone broth — Slow-simmering bones releases collagen that breaks down into proline, hydroxyproline, and glycine — one of the richest natural sources available.
• Egg whites — A concentrated source of free L-proline and other amino acids important for collagen synthesis.
• Meat (especially tough cuts with connective tissue — shanks, oxtail, brisket) — Connective tissue-rich cuts deliver proline and hydroxyproline directly; the more collagen in the cut, the higher the proline content.
• Fish (especially skin-on and whole fish) — Fish skin and scales are rich in marine collagen, which is high in proline and hydroxyproline and is well absorbed by humans.
• Dairy (particularly hard aged cheeses and cottage cheese) — Casein and whey proteins contain meaningful amounts of proline; aged cheeses have higher concentrations due to protein breakdown during aging.

• Mild nausea or stomach upset at very high doses (above 5g at once)
• Loose stools if taken in large amounts on an empty stomach
• Theoretical concern at very high long-term doses in people with kidney disease (as with any amino acid supplement)
• Contraindicated in the rare genetic condition hyperprolinemia

• Recommended daily: 500–2,000 mg of L-Proline daily for general collagen support; up to 5,000 mg used in clinical/sports contexts, typically split across doses
• Best time of day: 30–60 minutes before exercise for tendon/joint support (to capitalize on the post-exercise collagen synthesis window); morning or before meals for skin and general collagen health
• With or without food: Can be taken with or without food; pairing with a vitamin C source (or a vitamin C supplement) is strongly recommended to enable full conversion to hydroxyproline
• Time to effect: 4–8 weeks for early changes; 12 weeks for meaningful skin, joint, or tendon improvements
• How long to take it: No cycling required — can be taken continuously. Most clinical benefits are measured at 8–12 weeks, with ongoing maintenance thereafter. Reassess need every 3–6 months.