Collagen peptides

What it is

Collagen is the main structural protein of skin, bone, tendon and cartilage; supplements are made by breaking animal collagen (usually bovine hide or bone, or fish skin) into short peptides that dissolve in water. As a dietary protein it is unusual in composition: it is rich in glycine, proline and hydroxyproline and low in the essential amino acids that drive muscle protein synthesis, which is why sports-nutrition reviewers describe it as a low-quality protein. The proposed mechanism for its effects is that these particular amino acids are taken up and used in collagen-containing tissues.

What the research says

The evidence here is unusual: several meta-analyses report statistically significant benefits, but the underlying trials are small, mostly in women, often of unclear risk of bias, and frequently supported by the companies that sell collagen. Pooled analyses find improvements in skin hydration and elasticity, and small-to-moderate reductions in osteoarthritis pain with improved joint function. In contrast, a 2024 review of collagen peptides for musculoskeletal performance found that 48 of 55 performance measures were unaffected and no significant effect on strength - and the reviewers documented manufacturer involvement in 11 of the 13 studies they examined. A second 2024 meta-analysis did find small strength and muscle-size effects but rated its own certainty of evidence as low. Reported harms are few; the clearest documented risk is allergy, since fish collagen is an IgE-binding allergen in a fifth of fish-allergic patients.

Evidence grade: Disputed.

What goes wrong

Fish collagen is an allergen: about a fifth of fish-allergic patients tested had IgE that bound to it, and it triggered functional IgE cross-linking. (Source 1)

• Survey study, Moderate certainty.
• Size: 101 fish-allergic patients.
• Who: Patients with diagnosed fish allergy.
• How long: Not applicable - laboratory immunoassay study.
• Result: 21 of 101 patients (21%) sensitised to collagen; 8 collagen-sensitised patients lacked parvalbumin-specific IgE to some fish species; functional IgE cross-linking shown in 6 sera plus 1 basophil activation test.
• Funding: not stated.

Twenty-one of 101 patients (21%) were sensitized to collagen.

What the evidence supports

A meta-analysis of collagen derivatives in osteoarthritis found small-to-moderate reductions in pain and improvement in function. (Source 2)

• Meta-analysis, Moderate certainty.
• Size: 35 RCTs with 3165 patients; main analysis 25 RCTs with 2856 patients.
• Who: Patients with osteoarthritis.
• How long: Not stated in abstract; trials searched to June 2023.
• Result: 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.
• Funding: not stated for the review; funding of included trials varied.

Collagen derivatives exerted small-to-moderate effects on pain alleviation (standardized mean difference [SMD] −0.35, 95% confidence interval [CI] −0.48 to −0.22, moderate certainty) and function improvement (SMD −0.31, 95%CI −0.41 to −0.22, high certainty) compared with the control.

In the same osteoarthritis meta-analysis, collagen did not increase withdrawals or adverse events compared with control. (Source 2)

• Meta-analysis, High certainty.
• Size: 35 RCTs, 3165 patients.
• Who: Patients with osteoarthritis.
• How long: Not stated in abstract.
• Result: No increased risk of withdrawal or adverse events versus control; trial sequential analysis judged to have sufficient power.
• Funding: not stated.

Collagen derivatives were safe; they did not increase the risk of withdrawal or adverse events compared with the control.

What the evidence does not support

A 2024 systematic review found most musculoskeletal performance measures unaffected by collagen peptides and no significant pooled effect on strength. (Source 3)

• Systematic review, Low certainty.
• Size: 13 studies reviewed, 9 in the meta-analysis; 55 performance parameters extracted.
• Who: Adults undertaking exercise training or recovering from training stimuli.
• How long: Not stated in abstract.
• Result: 48 of 55 performance parameters unaffected; strength SMD = 0.079 (95% CI -0.120 to 0.273), p = 0.445.
• Funding: not stated for the review itself.

Of the 55 performance parameters extracted, 48 were unaffected by additional CP intake. Furthermore, the meta-analysis revealed no significant effect of CP on strength-related performance parameters (SMD=0.079 [-0.120 to 0.273], p=0.445).

The reviewers of that null analysis documented collagen-industry involvement in 11 of the 13 studies they examined. (Source 4)

• Systematic review, Low certainty.
• Size: 13 studies assessed for financial ties.
• Who: Not applicable - assessment of funding and sponsorship.
• How long: Not applicable.
• Result: Financial support, contributions to study design, provision of supplements and assistance with manuscript preparation came from parties selling collagen peptides or sports nutrition supplements in 11 of 13 studies.
• Funding: industry ties documented in the included trials.

Financial support (4, 9, 20, 21, 22, 26, 29, 36, 43, 50), contributions to study design (20, 22), provision of dietary supplements (6, 9, 26, 36, 50), and assistance with manuscript preparation (20, 22, 26, 36, 50) were provided by individuals or companies associated with the sale of CP or sports nutrition supplements in general.

Where the evidence is mixed

An umbrella review of 16 systematic reviews found collagen supplementation consistently associated with favourable skin, musculoskeletal and osteoarthritis outcomes, and mixed results elsewhere. (Source 5)

• Review of reviews, Certainty not rated.
• Size: 16 systematic reviews covering 113 RCTs and 7983 patients, from 573 papers screened.
• Who: Adults across skin, musculoskeletal, osteoarthritis, oral health and cardiometabolic outcomes.
• How long: Not stated at umbrella level.
• Result: Consistent favourable pooled effects for skin, musculoskeletal health and osteoarthritis; mixed effects for oral health and cardiometabolic parameters; methodological quality of included reviews rated with AMSTAR 2 and evidence graded with GRADE.
• Funding: not stated.

In relation to skin, musculoskeletal health, and osteoarthritis conditions, collagen supplementation was consistently associated with favorable outcomes. Regarding oral health and cardiometabolic parameters, the impact of collagen supplementation yielded mixed results.

A meta-analysis of ten skin trials found increases in skin hydration and elasticity, but reported unclear risk of bias and too few studies to test for publication bias. (Source 6)

• Meta-analysis, Low certainty.
• Size: 10 randomised controlled trials with 646 participants.
• Who: Mostly female adults; the authors state the findings are more applicable to females.
• How long: Studies published 2010-2021; duration not stated in abstract.
• Result: Skin hydration SMD 1.25 (CI 0.77-1.74); elasticity SMD 0.61 (CI 0.21-1.02); moderate heterogeneity I2 = 55.5-56.5%; most common dose 4 g/day, median 3.5 g/day.
• Funding: not stated.

The risk of bias was generally unclear, and publication bias could not be assessed due to the small number of studies.

A separate 2024 meta-analysis did find small increases in muscle size and strength with collagen peptides plus resistance training, but rated the certainty of that evidence as low. (Source 7)

• Meta-analysis, Low certainty.
• Size: 9 RCTs, 385 subjects (muscle size measured in 175 subjects across 5 studies)
• Who: Adults aged approximately 18-65, training status from untrained to resistance trained.
• How long: At least 8 weeks, resistance training three times a week; 5 g to 15 g CP daily.
• Result: Muscle size ES = 0.35, p = .002, I2 = 0%, CI [0.13, 0.57]; maximal strength ES = 0.23, p < .01 (the paper prints the same CI [0.13, 0.57] for strength, which cannot match an effect of 0.23; see caveat)
• Funding: not stated.

Limit of this finding: The source paper prints the same 95% confidence interval, 0.13 to 0.57, for both the muscle-size effect (0.35) and the strength effect (0.23). That interval is centred on 0.35, so it cannot be correct for the strength estimate; one of the two is a printing error in the original paper. Treat the strength result as reported to be statistically significant, but do not rely on its stated confidence interval. The authors themselves rate the certainty of both results as low.

Overall, certainty of evidence for both parameters was low due to wide confidence intervals and varying training status of subjects.

Where the research disagrees

Whether collagen peptides improve muscle strength and performance when added to training

• Kirmse et al., German Journal of Sports Medicine (2024), systematic review with meta-analysis of 13 studies, 9 pooled: Of the 55 performance parameters extracted, 48 were unaffected by additional CP intake. Furthermore, the meta-analysis revealed no significant effect of CP on strength-related performance parameters (SMD=0.079 [-0.120 to 0.273], p=0.445). (Source 3)
• Current Issues in Sport Science meta-analysis (2024), meta-analysis of 9 RCTs, self-rated low certainty of evidence: Nine studies including 385 subjects resulted in a significantly higher maximal strength following CP supplementation (ES = 0.23, p < .01, I² = 0.01%, CI [0.13, 0.57], Figure 1) compared to placebo. (Source 7)

How much weight to put on the positive skin and joint pooled results

• Umbrella review, Aesthetic Surgery Journal Open Forum (2026), umbrella review of 16 systematic reviews, 113 RCTs, 7983 patients: Collagen supplementation demonstrates consistent and clinically meaningful benefits for dermal, bone, and muscular health. (Source 5)
• Indian Journal of Dermatology, Venereology and Leprology meta-analysis (2025), meta-analysis of 10 RCTs, 646 participants: The risk of bias was generally unclear, and publication bias could not be assessed due to the small number of studies. (Source 6)

How much

• Reference intake: No reference intake, RDA or adequate intake exists for collagen or collagen peptides: collagen is a dietary protein that the body also makes, not an essential nutrient, and no authority has set an intake for it. Reviewers characterise it as a low-quality protein because of its amino acid profile. (Source 8)
• Upper limit: No tolerable upper intake level or acceptable daily intake has been set by EFSA or any other body for collagen peptides. The closest thing to a safety statement in the pooled literature is the osteoarthritis meta-analysis finding no increase in adverse events or withdrawals versus control. (Source 2)
• Studied: Skin trials most commonly used 4 g/day, with a median of 3.5 g/day and a range of 1-10 g/day. (Source 6)
• Studied: Resistance-training trials gave 5 g/day (2 studies) to 15 g/day (7 studies) for at least 8 weeks. (Source 7)

A common belief, and what the research shows

The belief: Collagen supplements are proven to rebuild your skin and joints, and the science is settled.

What the research shows: Pooled results are positive but the trials behind them are small and often conflicted. A 2024 review of the exercise literature found that Of the 55 performance parameters extracted, 48 were unaffected by additional CP intake, and its authors recorded that Financial support (4, 9, 20, 21, 22, 26, 29, 36, 43, 50), contributions to study design (20, 22), provision of dietary supplements (6, 9, 26, 36, 50), and assistance with manuscript preparation (20, 22, 26, 36, 50) were provided by individuals or companies associated with the sale of CP or sports nutrition supplements in general. Even the positive skin meta-analysis states that The risk of bias was generally unclear, and publication bias could not be assessed due to the small number of studies, and the positive strength meta-analysis concedes that Overall, certainty of evidence for both parameters was low due to wide confidence intervals and varying training status of subjects. The osteoarthritis evidence is the strongest of the set, with pain SMD −0.35, 95% confidence interval [CI] −0.48 to −0.22, moderate certainty.

Questions and answers

What is it?

Collagen is a structural protein found in animal skin, bone and connective tissue. Collagen peptide supplements are collagen broken into short pieces (a hydrolysate). Its building blocks are unusual: it is very high in glycine and proline, and it is one of the few animal proteins that contains hydroxyproline. (Source 9)

What does it do in the body?

Earlier studies, summarised by the authors, found that free amino acids and small collagen fragments (di- and tripeptides) turn up in the blood after someone swallows collagen hydrolysate. In this small crossover study (6 volunteers, funded and partly run by a collagen manufacturer), total hydroxyproline in blood exceeded free hydroxyproline, pointing to uptake of hydroxyproline-containing fragments. What those fragments then do in skin or joints has not been shown: the authors state that a simple cause-and-effect relationship to explain the benefits cannot be established. (Source 9)

Is it good or bad for you?

For skin, the answer depends on which studies you count. A 2025 meta-analysis of 23 randomised trials (1,474 participants) found benefits overall. When the authors looked only at trials not funded by companies, or only at high-quality trials, those benefits disappeared. The authors concluded that there is currently no clinical evidence that collagen supplements prevent or treat skin ageing. Reported harms are few (see getRidOf). (Source 10)

How do you get more of it?

The body makes its own collagen. Making it requires enzymes that form hydroxyproline and hydroxylysine, and those enzymes depend on vitamin C (ascorbic acid). In studies, extra collagen protein comes from eating collagen-rich animal tissue, gelatin or hydrolysate supplements. (Source 11)

If it is harmful, what reduces it?

Does not apply. Collagen is a normal body protein and a normal part of the diet, not something to reduce. A 2019 systematic review of 11 studies (805 patients) on oral collagen for skin described supplementation as generally safe, with no reported adverse events. (Source 12)

Why might someone be low in it or missing it?

Collagen production falls with age. In a laboratory study, skin cells taken from people aged 80 and over produced less type I procollagen than cells from people aged 18 to 29 (56 versus 82 ng/ml). The authors link this to ageing of the cells and to less mechanical stimulation in aged skin. Low vitamin C (scurvy) also blocks the final steps of making collagen (see ifAbsent). (Source 13)

Which whole foods contain it or feed it?

Collagen comes only from animal foods, which is why hydroxyproline is a tell-tale marker of it: skin, bone, cartilage and connective tissue, and foods made from them such as gelatin. Plant foods contain no collagen. We could not reach the laboratory analysis of bone broth's collagen content (see notes), so we make no claim about how much broth provides. (Source 9)

What happens if you do not have it?

Eating collagen is not essential, because the body builds it from other protein. What causes disease is the body failing to make collagen properly. The classic example is vitamin C deficiency (scurvy), which leads to skin changes, poor wound healing, gum and dental disease, brittle bones and bleeding. (Source 11)

How can you test for it?

There is no validated consumer or clinical test of 'collagen level' or of whether someone would benefit from collagen supplements. Collagen breakdown products such as urinary hydroxyproline (OHP) have been used as markers of bone resorption in bone disease, not as a measure of collagen status. (Source 14)

We searched: WebSearch for urinary hydroxyproline as a marker of collagen breakdown and for collagen status testing; the closest source is a 1993 study comparing urinary collagen crosslinks with hydroxyproline in Paget's disease of bone. PubMed was CAPTCHA-blocked.

References

1. The Journal of Allergy and Clinical Immunology: In Practice. Collagen - An Important Fish Allergen for Improved Diagnosis. 2020. DOI 10.1016/j.jaip.2020.04.063. Read the source
2. Osteoarthritis and Cartilage. Efficacy and safety of collagen derivatives for osteoarthritis: A trial sequential meta-analysis. 2024. DOI 10.1016/j.joca.2023.12.010. Read the source
3. Deutsche Zeitschrift für Sportmedizin (German Journal of Sports Medicine). Collagen Peptide Supplementation and Musculoskeletal Performance: A Systematic Review and Meta-Analysis. 2024. DOI 10.5960/dzsm.2024.605. Read the source
4. Deutsche Zeitschrift für Sportmedizin (German Journal of Sports Medicine). Collagen Peptide Supplementation and Musculoskeletal Performance: A Systematic Review and Meta-Analysis (passage on industry involvement in the included studies). 2024. DOI 10.5960/dzsm.2024.605. Read the source
5. Aesthetic Surgery Journal Open Forum (Oxford Academic). Collagen Supplementation for Skin and Musculoskeletal Health: An Umbrella Review of Meta-Analyses on Elasticity, Hydration, and Structural Outcomes. 2026. DOI 10.1093/asjof/ojag018. Read the source
6. Indian Journal of Dermatology, Venereology and Leprology. Effects of collagen-based supplements on skin's hydration and elasticity: A systematic review and meta-analysis. 2025. DOI 10.25259/IJDVL_1165_2023. Read the source
7. Current Issues in Sport Science (CISS). Impact of collagen peptide supplementation together with long-term resistance training on maximal strength and muscle size in healthy adults - A systematic review and meta-analysis. 2024. Read the source
8. Current Issues in Sport Science (CISS). Impact of collagen peptide supplementation together with long-term resistance training on maximal strength and muscle size in healthy adults - A systematic review and meta-analysis (introduction). 2024. Read the source
9. Frontiers in Nutrition. Absorption of bioactive peptides following collagen hydrolysate intake: a randomized, double-blind crossover study in healthy individuals. 2024. DOI 10.3389/fnut.2024.1416643. Read the source
10. The American Journal of Medicine. Effects of Collagen Supplements on Skin Aging: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. 2025. DOI 10.1016/j.amjmed.2025.04.034. Read the source
11. Diseases (MDPI). Scurvy: Rediscovering a Forgotten Disease. 2023. DOI 10.3390/diseases11020078. Read the source
12. Journal of Drugs in Dermatology. Oral Collagen Supplementation: A Systematic Review of Dermatological Applications. 2019. PMID 30681787. Read the source
13. The American Journal of Pathology. Decreased Collagen Production in Chronologically Aged Skin: Roles of Age-Dependent Alteration in Fibroblast Function and Defective Mechanical Stimulation. 2006. DOI 10.2353/ajpath.2006.051302. Read the source
14. Bone and Mineral. Urinary collagen crosslink excretion: a better index of bone resorption than hydroxyproline in Paget's disease of bone?. 1993. DOI 10.1016/S0169-6009(08)80076-1. Read the source