What does the research show about collagen?

Collagen

Pooled trials report better skin hydration, elasticity and wrinkles, but a 2025 meta-analysis found the effect only in industry-funded and low-quality trials. Osteoarthritis symptom scores fell modestly, and two narrative reviews report less joint pain. With training, tendons grew larger and stiffer in two reviews, and strength findings disagree. A review of 25 skin trials reported few adverse events.

Add to Bio HackChecked 2026-11-09

Status: Dietary supplement or food in the US.
Also called: collagen peptides, hydrolyzed collagen, collagen hydrolysate, gelatin, marine collagen, bovine collagen, undenatured type II collagen, UC-II, Verisol, Fortigel, Peptan
Taken for: joint pain, tendons, ligaments, injury recovery, skin aging, wrinkles, skin hydration, hair and nails, muscle gain, bone density

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help5

StrongShown to improve tendon size alongside training in healthy adults, with stiffness gains at 15 to 30 g a day, though certainty was very low.
StrongShown to ease joint pain and improve joint function in recreational athletes and others, in reviews that did not pool results.
ModerateShown to lower total osteoarthritis scores by about 8 points and lower pain ratings, though the WOMAC pain subscore did not change.
LimitedLimited evidence: 15 g of vitamin C-enriched gelatin doubled a blood marker of collagen synthesis in 8 men. Injury studies were sparse and low certainty.
LimitedOne trial found 1,000 mg a day of fish collagen peptides increased hair diameter over 24 weeks in 114 women with thinning hair.

Reported risks2

ModerateIn skin trials, effects appeared only in pharmaceutical company funded and low-quality trials, not in unfunded or high-quality ones.How often is not known
LimitedLimited evidence: in 30 sports protein products sold in China, every product held at least one target metal, with mercury low in collagen samples.How often is not known

What people take it for, and what was found

Shown to help5

Strong

Tendon size and stiffness with training

Shown to improve tendon size alongside training in healthy adults, with stiffness gains at 15 to 30 g a day, though certainty was very low.

The numbers and sources

Effect: Across 19 RCTs (768 healthy adults) training for 8 weeks or more, collagen peptides improved tendon morphology (SMD 0.67) [1]. In a systematic review of 8 RCTs (257 people, 246 of them men) with resistance or plyometric training for 3 to 15 weeks, tendon cross-sectional area grew more on collagen than placebo in 3 of 4 studies. Tendon stiffness rose more on collagen in the 2 studies using 15 to 30 g a day, and the studies using about 5 g a day showed within-group changes only [2].
Population: Healthy adults over 17 in exercise programs [1]; trained adults aged 18 to 52 [2].
Sources: [1], [2]
Caveats: GRADE certainty for tendon outcomes was very low [1]. Trials were small and short, and nearly all participants were men [2]. The second review did not pool results [2].

Strong

Joint pain and function

Shown to ease joint pain and improve joint function in recreational athletes and others, in reviews that did not pool results.

The numbers and sources

Effect: A systematic review of 15 RCTs, 12 in recreational athletes, reported the most consistent benefit for joint function and joint pain [3]. A systematic review of 36 RCTs of type I collagen hydrolysate found joint studies reported less pain, better clinical scores, more mobility and better ankle function [4].
Population: Recreational athletes, older adults and premenopausal women [3]; RCTs of type I collagen alone, with varied populations and health conditions [4].
Sources: [3], [4]
Caveats: Both reviews are narrative, without pooled effect sizes, and heterogeneity among trials limits generalization [4]. In a 2026 trial in 74 healthy people with joint discomfort during activity, 40 mg a day of undenatured type II collagen for 180 days improved joint scores, but so did placebo, and between-group differences appeared only in subgroups [5].

Moderate

Osteoarthritis symptoms

Shown to lower total osteoarthritis scores by about 8 points and lower pain ratings, though the WOMAC pain subscore did not change.

The numbers and sources

Effect: In placebo-controlled trials, collagen lowered total WOMAC score by 8.00 points (95% CI -13.04 to -2.95) and VAS pain by 16.57 points (95% CI -26.24 to -6.89). Within WOMAC, stiffness fell (-0.41) but the pain (-0.22, 95% CI -1.58 to 1.13) and function subscores did not change [9].
Population: Adults with osteoarthritis [9].
Sources: [9]
Caveats: The pain subscore and the separate VAS pain score point in different directions. The abstract does not report the number of trials or their funding.

Limited

Collagen synthesis and tendon or ligament injury

Limited evidence: 15 g of vitamin C-enriched gelatin doubled a blood marker of collagen synthesis in 8 men. Injury studies were sparse and low certainty.

The numbers and sources

Effect: In 8 healthy men, 15 g of vitamin C-enriched gelatin taken 1 hour before 6 minutes of rope skipping doubled a blood marker of collagen synthesis (amino-terminal propeptide of collagen I). The abstract reports this doubling for the 15 g dose, not the 5 g dose [11]. A systematic review of 15 RCTs reported collagen synthesis rates were raised with 15 g a day [3]. A 2026 review of 6 studies in tendon and ligament tears, repairs and related conditions found collagen-based treatments associated with better pain, function, analgesic use or imaging results [12].
Population: 8 healthy men, crossover [11]; 15 RCTs, mostly recreational athletes [3]; people with tendon or ligament tears, after ACL reconstruction or rotator cuff repair, and with tendinopathy or ankle instability [12].
Sources: [3], [11], [12]
Caveats: Blood markers and engineered ligaments in a lab, not injury rates [11]. In the injury review, most oral products contained several ingredients besides collagen, and its authors rated the evidence sparse and low certainty [12].

LimitedStudied in women

Hair thickness

One trial found 1,000 mg a day of fish collagen peptides increased hair diameter over 24 weeks in 114 women with thinning hair.

The numbers and sources

Effect: In 114 women aged 20 to 50 with self-reported hair thinning, 1,000 mg a day of low-molecular-weight fish collagen peptides for 24 weeks increased hair diameter against placebo at week 24 [14].
Population: 114 women [14].
Sources: [14]
Caveats: One trial of one product. No trial of nails was located.

Mixed results3

Moderate

Skin aging: hydration, elasticity and wrinkles

Mixed results: pooled trials found better skin hydration and elasticity, but the effect appeared only in industry-funded trials and not in high-quality trials.

The numbers and sources

Effect: Across 23 RCTs (1,474 participants), collagen improved skin hydration, elasticity and wrinkles overall. Trials without pharmaceutical company funding showed no effect on any of the three, while funded trials did. High-quality trials showed no effect in any category [6]. Two earlier meta-analyses, of 19 RCTs (1,125 participants, 95% women) and 26 RCTs (1,721 participants), reported improved hydration and elasticity against placebo [7][8].
Population: Adults aged 20 to 70, mostly women [7].
Sources: [6], [7], [8]
Caveats: The sources disagree. The pooled positive results [7][8] did not separate trials by funding source; when that was done, the effect was confined to funded trials [6].

Limited

Muscle mass and strength with training

Limited evidence: one review found gains in fat-free mass and strength with training, while 8 training trials found collagen added no strength gain.

The numbers and sources

Effect: Across 19 RCTs (768 healthy adults) training for 8 weeks or more, collagen peptides improved fat-free mass (SMD 0.48), muscle architecture (SMD 0.39), maximal strength (SMD 0.19) and 48-hour reactive strength recovery (SMD 0.43) [1]. A 2025 meta-analysis found muscle performance improved (SMD 0.60, 95% CI 0.05 to 1.15) [10]. In 8 training RCTs, strength rose with training in every trial, and collagen added no further gain [2].
Population: Healthy adults over 17 in exercise programs [1]; people in RCTs of collagen with or without calcium and vitamin D [10]; trained adults aged 18 to 52 [2].
Sources: [1], [10], [2]
Caveats: Sources disagree on strength. GRADE certainty was moderate for body composition and low for the other outcomes [1]. A systematic review found collagen did not raise muscle protein synthesis compared with isonitrogenous higher-quality proteins [3].

Limited

Bone density

Limited evidence: one review found higher bone density, partly with added calcium and vitamin D, while another found the bone studies too limited to conclude.

The numbers and sources

Effect: A 2025 meta-analysis found collagen peptides raised bone mineral density at the femoral neck and spine (I² 80.1%) and improved bone turnover markers (SMD 0.40 to 0.58) [10]. A systematic review of 36 RCTs found limitations in the bone studies that prevent definitive conclusions [4]. In 39 older adults after total hip replacement, 15 g a day of collagen for 14 days did not change bone turnover markers [13].
Population: People in RCTs, some given calcium and vitamin D with collagen [10]; RCTs of type I collagen alone [4]; older adults after hip surgery [13].
Sources: [10], [4], [13]
Caveats: Sources disagree. Heterogeneity for bone density was high, and the meta-analysis pooled collagen alone and with calcium and vitamin D [10]. The abstract does not report fracture results [10].

Doses studied

Collagen synthesis studies used 15 g a day [3] and 5 or 15 g of vitamin C-enriched gelatin three times a day before activity [11]. Training trials ran 8 weeks or more [1]. Tendon trials that found stiffness gains used 15 to 30 g a day, with vitamin C [2]. The hair trial used 1,000 mg a day for 24 weeks [14]. Skin trials were summarized at about 90 days of use [7].

Risks

Reported risks2

LimitedHow often is not known

Heavy metals in tested products

Limited evidence: in 30 sports protein products sold in China, every product held at least one target metal, with mercury low in collagen samples.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In 30 sports protein supplements sold in China, including collagen, mercury was under 0.01 mg/kg in nearly all samples; one collagen sample reached 0.02 mg/kg. Every product contained at least one target metal [16].
Population: Product testing [16].
Sources: [16]
Caveats: One market and few collagen samples. The abstract does not report lead or cadmium for collagen separately.

ModerateHow often is not known

Funding bias in the evidence base

In skin trials, effects appeared only in pharmaceutical company funded and low-quality trials, not in unfunded or high-quality ones.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In the skin literature, effects appeared in pharmaceutical company funded trials and low-quality trials, and not in unfunded or high-quality trials [6].
Population: 23 skin RCTs [6].
Sources: [6]
Caveats: Funding analysis has not been published for the joint or tendon trials located here.

Checked, no increase found1

Limited

Adverse effects

Limited evidence: a review of 25 skin trials found adverse events infrequent, though most trials were at high risk of bias.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: A systematic review of 25 RCTs of oral hydrolyzed collagen for skin found it generally well tolerated, with a low incidence of adverse events [15]. No pooled analysis of adverse event rates was located.
Population: Adults in RCTs of 13 to 236 participants, mostly healthy volunteers [15].
Sources: [15]
Caveats: The abstract does not give event counts, and most included trials were at high risk of bias [15].

Claims tested and not found

That collagen reverses skin aging in independent trials. Trials without industry funding showed no effect on hydration, elasticity or wrinkles [6].
That collagen builds muscle like other protein. It did not raise muscle protein synthesis compared with higher-quality protein [3].

Sources

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 Medicine. 2024. https://doi.org/10.1007/s40279-024-02079-0
Buchalski A, Jeanfavre M, Altorelli C, et al. Collagen Supplementation on Tendon-Related Structural and Performance Outcomes: A Systematic Review. Journal of Functional Morphology and Kinesiology. 2026. https://doi.org/10.3390/jfmk11010130
Khatri M, Naughton RJ, Clifford T, et al. The effects of collagen peptide supplementation on body composition, collagen synthesis, and recovery from joint injury and exercise: a systematic review. Amino Acids. 2021. https://doi.org/10.1007/s00726-021-03072-x
Brueckheimer PJ, Costa Silva T, Rodrigues L, et al. The Effects of Type I Collagen Hydrolysate Supplementation on Bones, Muscles, and Joints: A Systematic Review. Orthopedic Reviews. 2025. https://doi.org/10.52965/001c.129086
Möller I, Martínez K, Terradillos-Guillén A, et al. Efficacy and tolerability of native (undenatured) type II collagen supplementation for joint health in healthy volunteers: a randomized double-blind placebo-controlled study. Nutrition Journal. 2026. https://doi.org/10.1186/s12937-026-01302-0
Myung SK, Park Y. Effects of Collagen Supplements on Skin Aging: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. American Journal of Medicine. 2025. https://doi.org/10.1016/j.amjmed.2025.04.034
de Miranda RB, Weimer P, Rossi RC. Effects of hydrolyzed collagen supplementation on skin aging: a systematic review and meta-analysis. International Journal of Dermatology. 2021. https://doi.org/10.1111/ijd.15518
Pu SY, Huang YL, Pu CM, et al. Effects of Oral Collagen for Skin Anti-Aging: A Systematic Review and Meta-Analysis. Nutrients. 2023. https://doi.org/10.3390/nu15092080
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. International Orthopaedics. 2018. https://doi.org/10.1007/s00264-018-4211-5
Sun C, Yang A, Teng F, et al. Efficacy of collagen peptide supplementation on bone and muscle health: a meta-analysis. Frontiers in Nutrition. 2025. https://doi.org/10.3389/fnut.2025.1646090
Shaw G, Lee-Barthel A, Ross ML, et al. Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. American Journal of Clinical Nutrition. 2017. https://doi.org/10.3945/ajcn.116.138594
Latini L, Porta F, Vitale N, et al. Clinical evidence for low-molecular-weight collagen peptides in tendon and ligament tears: a systematic review with narrative synthesis. Frontiers in Medicine. 2026. https://doi.org/10.3389/fmed.2026.1891011
Monsegue AP, Thudium CS, Wilms EJC, et al. Collagen protein supplementation does not modulate biomarkers of bone metabolism following total hip arthroplasty: a randomized, double-blind, placebo-controlled trial. Clinical Nutrition ESPEN. 2026. https://doi.org/10.1016/j.clnesp.2026.103253
Hwang S, Won J, Kim S, et al. Low-Molecular-Weight Collagen Peptide Supplementation Improves Cellulite Severity, Skin Elasticity, and Hair Shaft Diameter: A Clinical Study with Pharmacokinetic Evaluation. Journal of Medicinal Food. 2026. https://doi.org/10.1177/1096620x261428336
Bassila C, Bassila JC, Slim M. Efficacy and safety of hydrolyzed collagen supplementation on skin health outcomes: a systematic literature review of randomized controlled trials. European Journal of Clinical Nutrition. 2026. https://doi.org/10.1038/s41430-026-01778-3
Chen M, Dong R, Lai W. Heavy metal and Microplastic exposure from sports protein Supplements: Integrated health risk modeling and scenario analysis. Environmental Research. 2026. https://doi.org/10.1016/j.envres.2026.123988

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