Supplements

Collagen Peptides

Updated · 24 sources · Editorial policy

Collagen peptides, also sold as hydrolyzed collagen or collagen hydrolysate, are collagen from animal skin, bone, cartilage or fish scales that has been broken down into short protein fragments. Gelatin is the same protein in a less broken-down form. The powder dissolves in cold liquids and is marketed for joints, tendons, skin and, more recently, body composition.

The single most important fact: collagen is an incomplete protein. It contains no tryptophan and very little leucine, and in head-to-head trials it stimulates muscle protein synthesis far less than whey. Its claimed benefits rest instead on specific collagen-derived peptides, such as prolyl-hydroxyproline (Pro-Hyp), that reach the blood intact. Trials on joint pain, tendons and skin report small positive effects, but many are small, industry-supported or at high risk of bias.

This page summarizes what the clinical trials and meta-analyses report. It is for education only and is not medical advice.

Property Detail
Type Food protein / dietary supplement; enzymatically hydrolyzed collagen (gelatin is the less-hydrolyzed form)
Sources studied Pig skin, chicken feet, cartilage, fish skin and scales, jellyfish
Route Oral (powder, capsules, drinks)
Doses used in trials 2.5–15 g/day in most trials of functional outcomes (per a 2019 review); 5 g/day in tendon trials; 15 g/day in most body-composition trials; 30–35 g servings in whey comparisons
Blood kinetics Hydroxyproline-containing peptides (mainly Pro-Hyp) peak 1–2 h after a dose and fall to half of peak by ≈4 h
Protein quality Lacks tryptophan, so it scores as an incomplete protein (PDCAAS)
Leucine ≈1.0 g per 35 g of collagen peptides vs ≈3.0 g per 35 g of whey in one trial
WADA status Not named on the WADA 2026 Prohibited List

What it is

Collagen is the main structural protein of tendons, ligaments, skin, cartilage and bone. Its chains are rich in glycine, proline and hydroxyproline. Gelatin is a food derivative of collagen (Shaw et al., AJCN 2017), and collagen peptides are gelatin broken down further into shorter fragments. A product used in one body-composition trial, for example, was derived from type I collagen and had a mean molecular weight of about 3 kDa (Zdzieblik et al., Br J Nutr 2015).

The amino acid profile is very different from that of a typical “complete” protein. One trial in older women published the per-serving composition of the two supplements it compared (Oikawa et al., AJCN 2020):

Amino acid (g per ≈30 g serving) Whey protein Collagen peptides
Glycine 0.5 8.0
Proline 1.4 4.5
Leucine 4.3 0.9
Lysine 3.4 1.3
Tryptophan 0.7 0
Total essential amino acids 15.4 5.6

Collagen therefore supplies mostly non-essential amino acids, and almost none of the leucine that acts as the main trigger for muscle protein synthesis. Whey is covered on its own page: see whey protein.

How it works in the body

Absorption of di- and tripeptides

Most dietary protein is absorbed as free amino acids, but collagen hydrolysate is a partial exception. Its hydroxyproline-containing peptides resist breakdown and appear intact in human blood:

  • In healthy volunteers who took 9.4–23 g of gelatin hydrolysate from pig skin, chicken feet or cartilage after a fast, the peptide form of hydroxyproline rose from almost nothing to 20–60 nmol/mL of plasma. It peaked after 1–2 h and fell to half of the peak by 4 h. Pro-Hyp was the main peptide, with smaller amounts of Ala-Hyp, Leu-Hyp, Pro-Hyp-Gly and others (Iwai et al., J Agric Food Chem 2005).
  • In a single-blind crossover study of 5 healthy men, peptides made up about 30% of all hydroxyproline detected in blood. Fish-scale hydrolysate produced a larger total blood exposure than pig-skin hydrolysate, and the mix of peptides differed by source (Ohara et al., J Agric Food Chem 2007).

Proposed mechanisms

Two mechanisms are proposed, and neither is proven in human tissue:

  1. Signaling peptides. In cell culture, Pro-Hyp increased the migration and growth of fibroblasts (the cells that make collagen) taken from mouse skin (Shigemura et al., J Agric Food Chem 2009). This finding is often cited for the claim that collagen peptides “signal” skin and tendon cells; it has not been shown directly in people.
  2. Building blocks. Collagen raises blood glycine, proline and hydroxyproline, which tissues need to make new collagen. Whether supply of these amino acids limits collagen synthesis in healthy people is unclear.

What the research shows

Joint pain and osteoarthritis

Most joint trials are in knee osteoarthritis (OA). Several meta-analyses have pooled them:

Meta-analysis Trials (participants) Main result vs control
García-Coronado et al., Int Orthop 2019 Placebo-controlled RCTs of oral collagen in OA Total WOMAC score −8.00 (95% CI −13.04 to −2.95); VAS pain −16.57 (95% CI −26.24 to −6.89). WOMAC pain and function subscores not significant; stiffness subscore significant
Liang et al., Osteoarthritis Cartilage 2024 35 RCTs (3,165); main analysis 25 RCTs (2,856) Pain SMD −0.35 (95% CI −0.48 to −0.22, moderate certainty); function SMD −0.31 (95% CI −0.41 to −0.22, high certainty)
Simental-Mendía et al., Clin Exp Rheumatol 2025 11 RCTs (870), knee OA Pain MD −13.63 (95% CI −20.67 to −6.58; I² = 88%); function MD −6.46 (95% CI −9.52 to −3.40; I² = 75%)

WOMAC is a standard OA questionnaire covering pain, stiffness and function; VAS is a visual analog pain scale. The 2024 authors described their standardized mean differences (SMDs) of about −0.3 as small-to-moderate effects. A few points matter when reading these results:

  • “Collagen” covers different products. The 2024 analysis pooled “collagen derivatives,” not only hydrolyzed collagen, so its result does not apply to any single product.
  • Heterogeneity is high. In the 2025 analysis, I² values of 75–88% mean the trials disagreed considerably.
  • Not everyone agrees. A published critique of the 2019 meta-analysis argued that its pooled results “do not support strong conclusions” (von Hippel, Int Orthop 2021).

Other joint supplements have their own pages: glucosamine and chondroitin and MSM.

Tendons and connective tissue

The best-known study is a small mechanistic trial (Shaw et al., AJCN 2017). Design: randomized, double-blind crossover; n = 8 healthy, recreationally active young men. Each man took 0 (placebo), 5 or 15 g of gelatin in a drink containing 48 mg vitamin C, 1 h before 6 min of rope-skipping, three times a day for 3 days.

  • Blood glycine, proline, hydroxyproline and hydroxylysine rose with the gelatin dose and peaked 1 h after the drink.
  • With 15 g of gelatin, the blood marker of type I collagen synthesis (PINP, the N-terminal propeptide of type I collagen) doubled: the area under the PINP curve over 72 h was twice that of placebo or 5 g.
  • Serum taken after gelatin increased collagen content and improved the mechanics of engineered ligaments grown in the lab.

The study did not measure collagen synthesis inside a real tendon. PINP reflects type I collagen production across the whole body, including bone and skin.

A later biopsy study tested the idea directly in muscle (Aussieker et al., Med Sci Sports Exerc 2023). Design: randomized, double-blind, parallel; n = 45 recreational athletes (30 men, 15 women) received 30 g whey, 30 g collagen or a noncaloric placebo after one resistance exercise session. Over 5 h of recovery:

Outcome (%/h) Whey Collagen Placebo
Myofibrillar (muscle fiber) protein synthesis 0.041 0.036 0.032
Muscle connective protein synthesis 0.072 0.068 0.058

Only whey raised myofibrillar synthesis above placebo. Neither protein significantly increased connective protein synthesis (p = 0.09).

Longer training trials have measured tendon size by ultrasound or MRI:

Trial Design and n Dose and duration Result
Jerger et al., Scand J Med Sci Sports 2022 Randomized, placebo-controlled; 40 healthy young men, high-load resistance training 5 g/day, 14 weeks Achilles tendon cross-sectional area +11.0% vs +4.7% with placebo (p = 0.002); muscle thickness +7.3% vs +2.7%. Tendon stiffness and strength rose equally in both groups
Jerger et al., Eur J Sport Sci 2023 Randomized, placebo-controlled; 50 moderately active men, knee-extensor training 5 g/day, 14 weeks Greater patellar tendon cross-sectional area at 60% and 70% of tendon length. Tendon stiffness, muscle size and strength did not differ between groups
Praet et al., Nutrients 2019 Pilot randomized crossover; 20 patients with chronic Achilles tendinopathy, plus calf-strengthening exercise 6 months (3 months each arm) After 3 months, VISA-A symptom score rose 12.6 points with collagen first vs 5.3 points with placebo first

A 2024 meta-analysis found a larger tendon size with collagen (SMD 0.67) but rated the certainty of evidence for tendon outcomes as very low (Bischof et al., Sports Med 2024). In short, collagen raises blood levels of collagen building blocks and may add to training-induced tendon growth, but whether it makes tendons stronger or prevents injury has not been shown.

Research peptides promoted online for tendon healing, such as BPC-157, are a different category: they are not food proteins and lack controlled human trials.

Skin

Skin is the most heavily marketed use, and the meta-analyses diverge mainly on how they handle trial quality and funding:

Review Trials (participants) Finding
de Miranda et al., Int J Dermatol 2021 19 RCTs (1,125; 95% women, aged 20–70) Pooled results favored hydrolyzed collagen for hydration, elasticity and wrinkles, typically after ≈90 days
Pu et al., Nutrients 2023 26 RCTs (1,721) Improved skin hydration and elasticity; the authors noted several biases and called for larger trials
Myung and Park, Am J Med 2025 23 RCTs (1,474) All trials pooled: benefit. Trials without pharmaceutical-company funding, and high-quality trials, showed no effect on hydration, elasticity or wrinkles
Bassila et al., Eur J Clin Nutr 2026 25 RCTs (13–236 participants each) Most trials favored collagen, but the majority were rated at high risk of bias

The split by funding source in the 2025 analysis is the key caveat: the positive pooled result appears to depend largely on industry-funded trials.

Body composition with resistance training

Several trials, mostly with 15 g/day, report slightly larger fat-free mass gains when collagen is added to training. The most cited is in older men with sarcopenia (age-related loss of muscle) (Zdzieblik et al., Br J Nutr 2015). Design: randomized, double-blind, placebo-controlled; n = 53 men (mean age 72); 12 weeks of resistance training three times a week plus 15 g/day collagen peptides or a silica placebo.

Change over 12 weeks Collagen (n = 26) Placebo (n = 27)
Fat-free mass +4.2 kg +2.9 kg
Fat mass −5.4 kg −3.5 kg
Quadriceps strength +16.5 Nm +7.3 Nm

All differences were significant (p under 0.05). Two limits apply. The placebo contained no protein, so the collagen group simply ate 15 g/day more protein. And a 2025 correction states that the supplement maker provided the product and paid for participant compensation and sample analysis (corrigendum).

The 2024 meta-analysis pooled 19 studies with 768 participants and found effects in favor of collagen on fat-free mass (SMD 0.48, moderate certainty of evidence) and maximal strength (SMD 0.19, low certainty) (Bischof et al., Sports Med 2024). Its inclusion criteria allowed either calorie-matched or non-calorie placebos, so much of the comparison is collagen versus no extra protein.

Protein quality: collagen vs whey

When collagen is compared with an equal amount of a high-quality protein, it does less for muscle:

  • Older women. In a double-blind trial in 22 women (mean age 69), 30 g of whey or collagen twice daily for 6 days was compared. Whey raised both short-term and longer-term muscle protein synthesis; collagen did not raise longer-term synthesis above baseline, and blood leucine did not rise after collagen (Oikawa et al., AJCN 2020).
  • Young adults, leucine-matched. In 22 untrained young adults on a 10-week resistance program, 35 g of whey (3.0 g leucine) was compared with 35 g of collagen peptides (1.0 g leucine) plus 2.0 g of added free leucine. Whey still produced larger gains in vastus lateralis thickness (+8.4% vs +5.6%) and biceps thickness (+10.1% vs +6.0%). Strength and power gains were similar (Jacinto et al., IJSNEM 2022).
  • After exercise. In the 45-person biopsy study above, only whey increased muscle fiber protein synthesis above placebo (Aussieker et al., 2023).

Under the PDCAAS method (Protein Digestibility-Corrected Amino Acid Score), collagen lacks tryptophan and counts as an incomplete protein. One modeling study calculated that collagen could replace up to 36% of protein in a typical Western diet without falling short on essential amino acids; one of its authors provides research services to a collagen supplement maker (Paul et al., Nutrients 2019). In the trials above, collagen protein was therefore not equivalent to whey for building muscle, gram for gram.

Side effects and risks

Tolerability

Collagen peptides are a food protein and are generally well tolerated in trials:

  • In the 2024 OA meta-analysis, collagen derivatives did not increase withdrawals or adverse events compared with control (Liang et al., 2024).
  • The 2026 skin review reported a low incidence of adverse events (Bassila et al., 2026).
  • The Achilles tendinopathy pilot reported no adverse events (Praet et al., 2019).

Most trials lasted weeks to months, so long-term safety data are limited.

Quality and contamination

Because collagen is made from animal skin, bone and scales, contamination with toxic elements has been studied:

  • Marine collagen. An Italian government-funded analysis of fish and jellyfish collagen supplements found arsenic as the most abundant element (mean 0.59 mg/kg) followed by lead (0.13 mg/kg), with significant differences between brands. Mercury was detectable in 12% of samples. No sample exceeded EU limits, and estimated daily intakes stayed below tolerable levels (Cammilleri et al., Open Med 2025).
  • Sports protein powders, including collagen. A study of 30 protein supplements sold in China found at least one toxic metal in every sample; one collagen sample had the highest mercury value (0.02 mg/kg). Microplastics were found in all samples, at 2–19 particles per 30 g serving (Chen et al., Environ Res 2026).

In the second study, the modeled hazard index was 0.45 at 30 g/day and 0.90 at 90 g/day, mainly from arsenic and cadmium; the 95th percentile reached 1.28 under high-use conditions. Both studies found wide variation between products.

Key takeaways

  • Partly absorbed as peptides. Hydroxyproline-containing peptides, mainly Pro-Hyp, reach the blood intact and peak 1–2 h after a dose; their effects on human tissue are not proven.
  • Small effect on OA symptoms. Meta-analyses show small improvements in pain and function, with high heterogeneity and mixed products.
  • Tendon data are early. Gelatin plus vitamin C doubled a blood marker of collagen synthesis in 8 men, and two 14-week trials found larger tendon size, but tendon strength and injury outcomes are unproven.
  • Skin benefit depends on who funded the trial. Pooled results are positive, but independent and high-quality trials showed no effect in a 2025 meta-analysis.
  • A poor muscle-building protein. Collagen lacks tryptophan and has little leucine; whey beat it for muscle protein synthesis and muscle growth even when leucine was matched.
  • Product quality varies. Studies of marine collagen and sports protein powders found arsenic, lead, mercury and microplastics at levels that varied widely by brand; marine collagen samples stayed within EU limits.

Sources

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  3. Shigemura Y, Iwai K, Morimatsu F, et al. Effect of prolyl-hydroxyproline (Pro-Hyp), a food-derived collagen peptide in human blood, on growth of fibroblasts from mouse skin. J Agric Food Chem. 2009;57(2):444–449. PubMed.
  4. García-Coronado JM, Martínez-Olvera L, Elizondo-Omaña RE, et al. Effect of collagen supplementation on osteoarthritis symptoms: a meta-analysis of randomized placebo-controlled trials. Int Orthop. 2019;43(3):531–538. PubMed.
  5. von Hippel PT. Do collagen supplements reduce symptoms of osteoarthritis? Meta-analytic results do not support strong conclusions. Int Orthop. 2021;45(12):3283–3284. PubMed.
  6. Liang CW, Cheng HY, Lee YH, et al. Efficacy and safety of collagen derivatives for osteoarthritis: a trial sequential meta-analysis. Osteoarthritis Cartilage. 2024;32(5):574–584. PubMed.
  7. Simental-Mendía M, Ortega-Mata D, Acosta-Olivo CA, et al. Effect of collagen supplementation on knee osteoarthritis: an updated systematic review and meta-analysis of randomised controlled trials. Clin Exp Rheumatol. 2025;43(1):126–134. PubMed.
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  9. Aussieker T, Hilkens L, Holwerda AM, et al. Collagen protein ingestion during recovery from exercise does not increase muscle connective protein synthesis rates. Med Sci Sports Exerc. 2023;55(10):1792–1802. PubMed.
  10. Jerger S, Centner C, Lauber B, et al. Effects of specific collagen peptide supplementation combined with resistance training on Achilles tendon properties. Scand J Med Sci Sports. 2022;32(7):1131–1141. PubMed.
  11. Jerger S, Centner C, Lauber B, et al. Specific collagen peptides increase adaptions of patellar tendon morphology following 14-weeks of high-load resistance training: a randomized-controlled trial. Eur J Sport Sci. 2023;23(12):2329–2339. PubMed.
  12. Praet SFE, Purdam CR, Welvaert M, et al. Oral supplementation of specific collagen peptides combined with calf-strengthening exercises enhances function and reduces pain in Achilles tendinopathy patients. Nutrients. 2019;11(1):76. PubMed.
  13. Bischof K, Moitzi AM, Stafilidis S, et al. Impact of collagen peptide supplementation in combination with long-term physical training on strength, musculotendinous remodeling, functional recovery, and body composition in healthy adults: a systematic review with meta-analysis. Sports Med. 2024;54(11):2865–2888. PubMed.
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  19. Oikawa SY, Kamal MJ, Webb EK, et al. Whey protein but not collagen peptides stimulate acute and longer-term muscle protein synthesis with and without resistance exercise in healthy older women: a randomized controlled trial. Am J Clin Nutr. 2020;111(3):708–718. PubMed.
  20. Jacinto JL, Nunes JP, Gorissen SHM, et al. Whey protein supplementation is superior to leucine-matched collagen peptides to increase muscle thickness during a 10-week resistance training program in untrained young adults. Int J Sport Nutr Exerc Metab. 2022;32(3):133–143. PubMed.
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  24. World Anti-Doping Agency. The 2026 Prohibited List. WADA 2026 Prohibited List.