Collagen Peptides: Benefits, Forms, Dosing, and Side Effects

Collagen is the most abundant protein in the human body, forming the structural backbone of skin, bone, cartilage, tendons, blood vessels, and the cornea. It is uniquely rich in the amino acids glycine, proline, and hydroxyproline — the last being virtually exclusive to collagen and essential for its structural stability [1]. Adults lose approximately 1% of skin collagen per year, contributing to progressive thinning, wrinkling, and loss of elasticity [2].

Collagen supplements are derived from animal sources (bovine, porcine, fish, chicken, or eggshell membrane) and are available in several forms: hydrolyzed collagen (collagen peptides), gelatin, and undenatured collagen. Clinical evidence supports modest benefits for skin aging, joint pain, and bone density, though most studies are manufacturer-funded and effects are generally small.

Table of Contents

• Overview
• Forms and Bioavailability
• Evidence for Benefits
• Recommended Dosing
• Safety and Side Effects
• Drug Interactions
• Dietary Sources
• Frequently Asked Questions
• References

Overview

Collagen protein constitutes approximately 30% of total body protein. Types I and III predominate in skin, bone, and tendons, while type II is the primary collagen in cartilage [1]. There are at least 28 identified collagen types, but these three account for the vast majority of supplementation research.

The age-related loss of skin collagen may be more pronounced in women, who have lower baseline collagen density than men [2]. This decline also affects joints (contributing to cartilage thinning and osteoarthritis), bones (contributing to reduced bone mineral density), and other connective tissues. Preliminary evidence suggests that some collagen peptides may remain intact during absorption and accumulate in skin and cartilage tissue [3][4].

Collagen supplements are typically sourced from bovine (cow) hides and bones, porcine (pig) skin, chicken sternal cartilage, fish skin and scales, or eggshell membranes [1]. No plant-based organism produces collagen, although fermented amino acid alternatives (marketed as "vegan collagen") have recently been developed.

The evidence base is predominantly composed of small, manufacturer-funded studies with modest effect sizes. A 2025 systematic review found that when only high-quality, independent studies were analyzed, benefits on skin hydration and elasticity were no longer statistically significant [4]. The sections below review this evidence in detail.

Forms and Bioavailability

Collagen supplements are available in several distinct forms, each with different characteristics for absorption, application, and clinical evidence.

Hydrolyzed collagen (collagen peptides): Enzymatically broken down into small peptides, typically under 3,500 daltons for branded ingredients such as those manufactured by Gelita AG (Verisol, Tendoforte, Fortigel). Dissolves in cold or hot liquids. This is the most common and most-studied supplemental form [1]. When collagen is hydrolyzed to peptides, a molecule of water is added to each peptide, slightly increasing weight — this is why protein content on supplement labels is typically about 90% of the listed collagen peptide weight.

Gelatin: Partially hydrolyzed collagen with larger peptides. Dissolves only in hot water. A study in healthy young men found amino acid bioavailability from gelatin was not significantly different from hydrolyzed peptides at an equal 20 g dose, while gelatin was more palatable and approximately one-quarter the cost [5].

Undenatured collagen (UC-II): Raw cartilage-derived collagen, primarily type II, from chicken sternal cartilage — only about 25% of UC-II is actual collagen, with the remainder consisting of glycosaminoglycans and other cartilage components. Its proposed mechanism involves immune modulation rather than direct collagen supply, explaining why clinical doses are much smaller (40 mg per day) than hydrolyzed collagen (typically 2.5–15 g/day) [1].

Eggshell membrane (NEM, BiovaFlex): A natural matrix of type I collagen, elastin, and small amounts of glucosamine and chondroitin. Primarily studied for joint health rather than skin. Typical dose is 450–500 mg/day in capsule form [1].

Vegan collagen alternatives (e.g., VeCollal): Not actual collagen but fermented amino acids in ratios mimicking type I human collagen, combined with herbal extracts. A manufacturer-conducted study in 90 healthy adults found 5 g/day of VeCollal for 8 weeks increased skin elasticity by 5.1% and skin hydration by 4.3% versus placebo — benefits similar to 5 g of fish collagen in the same trial [6].

Source Comparison: Bovine vs. Porcine vs. Marine

A clinical study comparing single 10 g doses of fish, porcine, and bovine collagen hydrolysate found similar increases in blood hydroxyproline levels across all three sources — no particular animal source appears to have superior oral bioavailability [7]. However, blood hydroxyproline levels needed to produce clinically meaningful changes in target tissues have not been determined.

Comparison Table

Form	Source	Typical Daily Dose	Dissolves In	Primary Clinical Uses
Hydrolyzed collagen (peptides)	Bovine, porcine, fish	2.5–15 g	Hot and cold liquids	Skin, joints, bone, general
Gelatin	Bovine, porcine	10–20 g	Hot liquids only	Skin, general protein
Undenatured collagen (UC-II)	Chicken cartilage	40 mg (~10 mg collagen)	Capsule form	Joint pain/osteoarthritis
Eggshell membrane (NEM, BiovaFlex)	Chicken eggshell	450–500 mg	Capsule form	Joint pain/stiffness
Vegan alternative (VeCollal)	Fermented amino acids	5 g	Hot and cold liquids	Skin (preliminary)

Key Bioavailability Principles

Dipeptide content matters: A study found that collagen hydrolysate enriched in specific dipeptides (proline-hydroxyproline and hydroxyproline-glycine at >3,000 ppm vs. <100 ppm in conventional peptides) provided similar joint benefits at a dose of 2.5 g compared to 10 g of conventional collagen peptides [10]. This suggests that the composition and molecular weight of collagen peptides may be as important as the total dose.

Collagen is not a complete protein: Collagen lacks the amino acid tryptophan entirely and is low in branched-chain amino acids (leucine, isoleucine, valine) critical for muscle protein synthesis [1][11]. A study in young healthy adults found no increase in muscle or connective tissue protein synthesis rates when 30 g of hydrolyzed collagen was consumed after resistance exercise compared to a noncaloric placebo [11]. For muscle building, whey or other complete proteins are substantially more effective [1][11].

Evidence for Benefits

Skin Aging and Wrinkles

The evidence for collagen supplementation and skin health is the most extensively studied application. A 2025 systematic review and meta-analysis of 23 clinical studies found that collagen supplementation (~3 g/day for ~12 weeks) modestly improved skin hydration and elasticity compared to placebo, but did NOT reduce wrinkles when only high-quality or independent studies were considered [4]. This review has been criticized for inaccurate classification of study funding and for incorrectly citing the duration and collagen source in certain included studies [12][13][14].

The best-studied branded ingredient is Verisol (Gelita AG), a porcine-derived type I collagen peptide:

• In 114 women aged 45–65, 2.5 g/day reduced eye wrinkle volume by 20.1% versus placebo at 8 weeks. Skin biopsies showed procollagen type I increased by 65% and elastin by 18%. Four weeks after stopping supplementation, wrinkle volume remained 11.5% lower than placebo [15].
• In women averaging age 48, 2.5 g or 5 g/day improved forearm skin elasticity after 2 months, with both doses equally effective. Benefits were greatest in women over 50 [16].
• In 66 women (average age 46), 2.5 g/day of bovine-derived Verisol B decreased eye wrinkle volume by 19% versus a 6% increase with placebo, with modest improvements in facial hydration and elasticity [17].
• In women (average age 40), 2.5 g/day for 6 months reduced the appearance of thigh cellulite by 9% and skin waviness by 8% compared to placebo [18].

Fish-derived collagen (5 g/day) improved cheek skin elasticity by 9–10% versus placebo after 1 month in postmenopausal women [19]. A separate study found 2 g/day of low-molecular-weight fish collagen for 12 weeks modestly reduced eye wrinkle depth (–11.2% vs. –5.9% placebo) [20].

A study adding 1.5 g MSM (methylsulfonylmethane) to fish collagen (5 or 10 g) plus 80 mg vitamin C found MSM improved skin roughness beyond what collagen plus vitamin C alone achieved, though MSM did not add benefit for wrinkle reduction. Both collagen doses reduced wrinkle volume by 17–20% versus placebo [26].

Negative finding: In 85 East Asian women (ages 43–65), 5 g/day of porcine collagen peptides for 12 weeks did not significantly improve skin elasticity, wrinkle depth, or perceived skin beauty when participants were already using a daily moisturizer. The researchers attributed the overall null result to a strong moisturizer placebo response [27].

Hair and Nails

Evidence for collagen's effects on hair and nails is limited and mixed. A study of 86 adults found 450 mg/day of chicken eggshell membrane hydrolysate for 3 months modestly increased hair density by computer analysis but did not increase hair growth or decrease hair breakage compared to placebo [29]. A separate study found 1 g/day of fish collagen for 24 weeks modestly increased hair strand diameter versus placebo [22].

For nails, a study of women taking 2.5 g/day of Verisol for 24 weeks reported that nail growth increased by 12% and broken nail frequency decreased by 42% compared to pre-supplementation. However, this study had no placebo control, limiting the strength of its conclusions [30].

Joint Pain and Osteoarthritis

Collagen supplementation for at least 3–6 months may modestly reduce joint stiffness and pain according to multiple studies. Results have been inconsistent, and several studies have shown no benefit.

Undenatured collagen (UC-II): In people with knee osteoarthritis, 40 mg/day of UC-II for 3 months improved pain, stiffness, and physical function while glucosamine (1,500 mg) plus chondroitin (1,200 mg) did not [32]. A 6-month placebo-controlled study found UC-II reduced average pain scores by 24 points versus 17 points for placebo, with significant stiffness reduction [33]. However, a 2025 study using 20 mg UC-II combined with hydrolyzed collagen found no benefit over placebo after 12 weeks — possibly due to the lower UC-II dose, the combination formula, or shorter duration [34].

Hydrolyzed collagen for joints: 1,200 mg/day reduced pain in 51.6% of participants versus 36.5% on placebo after 6 months — results at 3 months were not yet significant, suggesting longer supplementation is needed [36]. A large study (n=167) of 10 g/day collagen peptides found no benefit for knee pain, function, or inflammatory markers [40].

Eggshell membrane supplements: 500 mg/day of NEM (Natural Eggshell Membrane) for 1 month modestly improved knee function and reduced pain and stiffness in mild-to-moderate osteoarthritis, though it did not improve joint spacing [42][43]. A combination of NEM (500 mg) with 1,500 mg fish oil for 1 week showed 29% less post-exercise joint pain versus placebo, though differences did not persist through week 2 [73].

Bone Density

A 12-month study in 131 postmenopausal women with reduced bone mineral density found 5 g/day collagen peptides (Fortibone by Gelita AG) increased spine BMD by 3.0% and femoral neck BMD by 6.7%, versus decreases of 1.3% and 1.0% with placebo. Participants in both groups were encouraged to take calcium (500–800 mg) and vitamin D (400–800 IU) daily [46].

A 4-year follow-up of 23 women from the above study showed continued ~7% BMD improvements with no fractures, though this lacked a control group [47].

Muscle Mass and Strength

In older men (average age 72) with sarcopenia doing resistance training for 3 months, 15 g/day of collagen peptides (BODYBALANCE by Gelita AG) increased lean mass and strength significantly more than placebo [51]. In recreationally active men (average age 47), 30 g/day for 12 weeks did not improve strength or muscle thickness — collagen is low in branched-chain amino acids needed for muscle protein synthesis, and whey protein is substantially more effective for muscle building [52].

Blood Sugar

Small studies suggest fish collagen peptides may lower blood sugar through dipeptidyl peptidase 4 (DPP-4) inhibition — the same mechanism as prescription DPP-4 inhibitor medications [50]. In 61 people with type 2 diabetes, 5 g/day of fish collagen peptides for 3 months lowered fasting glucose by 78 mg/dL and reduced HbA1c from 8.1% to 5.9%. A 2.5 g dose was ineffective [48]. A second study (n=100) found 13 g/day reduced fasting glucose by 26 mg/dL and HbA1c by 0.48% versus control [49].

Tendon, Ligament, and Wound Healing

In 50 competitive athletes with chronic ankle instability, 5 g/day of hydrolyzed collagen (Tendoforte) during 6 months of home-based exercises improved subjective ankle function by 5.28 points (30-point scale) versus no significant improvement with placebo [58]. In 20 people with chronic Achilles tendinopathy, 2.5 g of Tendoforte twice daily before calf-strengthening exercises for 3 months enabled 6 of 10 people to return to running versus 3 of 10 in the placebo group [59].

For wound healing, studies using 1.5–10 g/day of hydrolyzed collagen in long-term care residents with pressure ulcers showed modestly better healing scores compared to placebo [53][54][55]. In 31 men with 20–30% body surface burns, 9 g of hydrolyzed collagen 4 times daily for 4 weeks resulted in 100% complete wound healing versus 40% in the standard-care control group [56].

Fatigue

In 62 healthy adults who reported being easily fatigued, 5 g of fish collagen peptide twice daily for 8 weeks improved fatigue scores on the Profile of Mood States from above the general population average (52.2) to below it (47.0), while the placebo group remained elevated (51.5). The collagen group also improved on vigor-activity scores [61].

Hyaluronic Acid (a Common Collagen Co-Ingredient)

Skin supplements frequently combine collagen with hyaluronic acid. A study of 40 healthy adults (average age 43) found 120 mg/day of hyaluronic acid for 12 weeks modestly reduced the visibility of crow's feet wrinkles and slightly reduced facial skin moisture loss compared to placebo [74].

Recommended Dosing

Goal	Form	Daily Dose	Duration to Benefit
Skin wrinkles/elasticity	Hydrolyzed collagen (Verisol or similar)	2.5–5 g	4–12 weeks
Cellulite reduction	Hydrolyzed collagen (Verisol)	2.5 g	3–6 months
Joint pain (osteoarthritis)	Hydrolyzed collagen peptides	5–10 g	3–6 months
Joint pain (osteoarthritis)	UC-II (undenatured type II)	40 mg (~10 mg collagen)	3–6 months
Joint pain	Eggshell membrane (NEM)	500 mg	4–12 weeks
Bone mineral density	Hydrolyzed collagen (Fortibone)	5 g	12+ months
Muscle mass (elderly with sarcopenia)	Hydrolyzed collagen peptides	15 g	3 months (with resistance training)
Tendon/ligament recovery	Hydrolyzed collagen (Tendoforte)	5 g	3–6 months
Blood sugar support (type 2 diabetes)	Fish collagen peptides	5–13 g	3 months
Wound healing (pressure ulcers)	Hydrolyzed collagen	1.5–10 g	4–16 weeks

Skin: Even doses as low as 0.5 g may provide some benefit, but the best evidence is with 2.5 g of well-characterized collagen peptides (e.g., Verisol). Doses of 5 g do not appear to provide additional benefit over 2.5 g for skin outcomes [1][16].

Joints: Hydrolyzed collagen for joint pain typically requires 5–10 g daily. UC-II uses a much smaller dose of 40 mg and works through a different mechanism — the two are not directly comparable on a weight basis. Benefits for joint pain may take 3 months to become apparent and may require up to 6 months [1][36].

Timing and mixing: Hydrolyzed collagen can be taken with or without food, mixed into hot or cold beverages. For tendon and ligament applications, some protocols recommend taking collagen 30–60 minutes before exercise [59]. UC-II is typically taken on an empty stomach at bedtime. Adding vitamin C does not appear to enhance skin benefits unless the individual is vitamin C deficient [25].

Powder vs. liquid: Liquid collagen products typically provide less collagen per serving and cost 3–6 times more per gram than collagen powders. They may also contain added sweeteners [1]. Collagen powders are generally the most cost-effective delivery method.

Safety and Side Effects

Collagen supplements are generally well tolerated [62]. Reported mild side effects include [63]:

• Gastrointestinal symptoms (bloating, mild discomfort, altered taste)
• Headache, dizziness, insomnia
• Decreased appetite
• Itchy or pustular skin rash, canker sores

Liver effects: Rarely, elevated liver enzymes have been reported with cartilage-derived type II collagen supplements [63][64]. At least one consumer report described elevated liver enzymes after starting collagen peptides (Fortibone), which normalized after discontinuation. No published case reports have established a causal link between collagen peptides and liver injury [1].

Kidney stone risk: High-dose collagen (30 g/day gelatin) increased urinary oxalate excretion by 43%, potentially raising kidney stone risk in susceptible individuals. Doses around 2 g did not significantly affect oxalate [66]. People with a history of calcium oxalate kidney stones may want to avoid very high doses (>10–15 g/day), though typical supplemental doses of 2.5–10 g have not been associated with kidney stone formation.

Allergic reactions: Fish collagen may trigger reactions in individuals sensitive to tropomyosin (shellfish allergen), even if they test negative for standard fish allergy panels [65]. People with egg allergies should avoid eggshell membrane products. Some collagen products may contain trace amounts of naturally occurring sulfite residue [1].

Tryptophan depletion: Collagen lacks tryptophan, a serotonin precursor. Typical supplement doses (2.5–15 g/day) are unlikely to affect mood, but very high doses without adequate dietary protein diversity could theoretically reduce serotonin in susceptible individuals [67][68].

BSE/Prion concern: There is a theoretical concern about bovine collagen and BSE ("mad cow disease"). This risk is considered extremely low because: (1) gelatin and collagen are derived from hides and connective tissue, not high-risk brain and spinal tissue; (2) the FDA requires collagen be sourced from cattle inspected for human consumption; and (3) processing significantly reduces any prion levels that might be present [69].

Breast cancer concern: Concern has been raised about whether collagen supplementation could affect breast cancer recurrence, based on observations that high collagen levels are found in recurrent tumors [70]. However, no clinical research has demonstrated that consuming collagen supplements promotes cancer or cancer recurrence in humans. The concern is based on tissue-level observations and mouse studies, not supplementation studies [1].

Calcium myth: Some sources claim collagen increases blood calcium levels, but this is not supported by clinical evidence. Collagen supplements contain only about 20–30 mg of calcium per serving, well below the 1,000–1,200 mg daily requirement [1].

Interference with laboratory tests: Collagen, gelatin, or collagen-rich foods should be avoided for at least 24 hours before blood or urine tests measuring hydroxyproline (used to monitor bone resorption and Paget disease). Collagen consumption does NOT affect newer bone turnover markers (CTX, NTX, s-PINP) used to monitor osteoporosis treatment [71][72].

Drug Interactions

• Diabetes medications (insulin, metformin, sulfonylureas such as glyburide) — collagen peptides above 2.5 g/day may additively lower blood sugar via DPP-4 inhibition [48][49][50]. Blood sugar should be monitored if collagen is added to an existing diabetes medication regimen.
• Bone turnover tests — avoid collagen/gelatin for at least 24 hours before hydroxyproline-based bone resorption tests. Newer markers (CTX, NTX, s-PINP) are unaffected [72].
• Calcium-containing medications — although some sources claim collagen increases calcium absorption and could cause hypercalcemia, this has not been demonstrated in clinical studies. Collagen supplements contain minimal calcium (20–30 mg per serving), well below the daily requirement [1].

No clinically significant drug interactions with collagen have been documented in published clinical trials. As with any supplement, individuals on multiple medications should inform their healthcare provider before starting collagen supplementation.

Dietary Sources

Collagen is obtained from animal connective tissues. The collagen content of bone broth varies widely (5–15 g per cup) depending on preparation time, temperature, and source bones — making it a less reliable method than a standardized supplement for achieving specific clinical doses [1].

Food	Notes
Bone broth	5–15 g per cup (varies widely with preparation time and source)
Chicken skin, pork skin	Rich in types I and III collagen
Fish skin and scales	Source of marine (type I) collagen
Beef tendon	Dense connective tissue, high collagen
Gelatin desserts	~6–10 g per serving; partially hydrolyzed collagen
Egg whites	Contain proline for collagen synthesis

Nutrients That Support Collagen Synthesis

Several nutrients serve as essential cofactors for the body's own collagen production:

• Vitamin C: Required for hydroxylation of proline to form hydroxyproline, the amino acid that gives collagen its structural stability. Severe deficiency (scurvy) results in impaired collagen synthesis. However, a clinical study found that adding 500 mg vitamin C to collagen supplementation did not enhance skin benefits [25]. Unless vitamin C intake is truly deficient, additional supplementation is unlikely to improve collagen-specific outcomes [1].
• Glycine and proline: Abundant in collagen itself, as well as in meat, dairy, and eggs.
• Copper: Required for lysyl oxidase, the enzyme that cross-links collagen fibers.
• Zinc: Involved in collagen synthesis and wound healing.

"Collagen booster" supplements: These typically contain vitamin C, proline, lysine, and sometimes herbal extracts, but do NOT contain actual collagen [1]. The typical diet already provides adequate amounts of these nutrients. For example, one such product provides 75 mg of lysine (a normal diet provides ~1,000 mg daily) and 50 mg of proline (a normal diet provides ~5,000 mg) — making the value proposition questionable.

Frequently Asked Questions

Does collagen actually work for wrinkles?

The evidence suggests a modest benefit. Multiple placebo-controlled trials show 7–20% improvement in wrinkle volume with daily collagen peptide supplementation for 4–12 weeks. However, a systematic review of 23 studies found that when only high-quality, independent studies were analyzed, the benefits were no longer statistically significant [4]. The best-supported regimen is 2.5 g/day of Verisol-type collagen peptides for at least 8 weeks [15].

Is collagen powder better than collagen pills?

Neither form is inherently superior. The key consideration is dose: most clinical studies used 2.5–10 g of collagen daily. Collagen pills typically provide 1–5 g per serving and may require multiple capsules, while powders easily deliver 5–15 g per scoop. Powders are generally more cost-effective per gram [1].

Is marine (fish) collagen better than bovine collagen?

A head-to-head comparison found no significant difference in absorption between fish, porcine, and bovine collagen hydrolysates [7]. The best-studied branded ingredient for skin (Verisol) was originally porcine-derived. Marine collagen is preferred by some for religious, dietary, or allergen reasons, but there is no strong evidence that one source is clinically superior.

Does bone broth provide enough collagen?

Bone broth contains collagen, but the amount varies widely (5–15 g per cup) depending on preparation time, temperature, and source bones. A well-prepared bone broth may provide a meaningful dose but is difficult to standardize. Bone broth is a reasonable food source but less reliable than a standardized supplement for achieving specific clinical doses [1].

Can collagen and whey protein be taken together?

Yes. They serve complementary purposes: whey provides branched-chain amino acids (especially leucine) for muscle protein synthesis, while collagen provides the specific amino acids (glycine, proline, hydroxyproline) used in connective tissue maintenance. Collagen is not an effective substitute for whey or other complete proteins for muscle building [1][11].

Does vitamin C improve collagen supplement effectiveness?

Vitamin C is essential for the body's own collagen synthesis, but clinical evidence does not support taking additional vitamin C with collagen supplements. A study found that adding 500 mg of vitamin C to collagen peptides did not enhance skin benefits [25]. Unless genuinely deficient in vitamin C, additional supplementation is unlikely to improve collagen outcomes [1].

How long do the benefits last after stopping collagen?

Limited data exists on this question. One study found that skin wrinkle improvements persisted for at least 4 weeks after stopping supplementation [15]. For bone density, a 4-year study showed continued benefits with ongoing supplementation, but no data exists on what happens after stopping [47].

Is collagen safe during pregnancy?

There are no clinical studies evaluating collagen supplementation specifically during pregnancy. While collagen is a naturally occurring protein found in food, pregnant individuals should consult their healthcare provider before starting any supplement.

References

1. ConsumerLab. Collagen Supplements Review. https://www.consumerlab.com/reviews/collagen-supplements-review-peptides-hydrolysate/collagen/

2. Proksch E et al. Oral supplementation of specific collagen peptides has beneficial effects on human skin physiology. Skin Pharmacol Physiol, 2014;27(1):47-55. https://doi.org/10.1159/000351376

3. Iwai K et al. Identification of food-derived collagen peptides in human blood after oral ingestion. J Agric Food Chem, 2005;53(16):6531-6. https://doi.org/10.1021/jf050206p

4. Myung SK et al. Efficacy of collagen supplementation on skin aging: A systematic review and meta-analysis. Am J Med, 2025. https://doi.org/10.1016/j.amjmed.2024.12.022

5. Alcock RD et al. Plasma amino acid concentrations after the ingestion of dairy and collagen proteins, in healthy active males. Front Nutr, 2019;6:67. https://doi.org/10.3389/fnut.2019.00067

6. Lin P et al. Plant-based collagen biomimetic for skin health: A randomized placebo-controlled trial. J Funct Food, 2024. https://doi.org/10.1016/j.jff.2024.106067

7. Virgilio N et al. Comparative bioavailability of collagen hydrolysates from bovine, porcine, and fish sources. Front Nutr, 2024. https://doi.org/10.3389/fnut.2024.1307596

8. Oesser S et al. Oral administration of 14C labeled gelatin hydrolysate leads to an accumulation of radioactivity in cartilage. J Nutr, 1999;129(10):1891-5. https://doi.org/10.1093/jn/129.10.1891

10. Devasia S et al. Double-Blind, Randomized, Controlled Study on the Effect of Oral Collagen Peptide Supplementation on Knee Joint Comfort. Cartilage, 2024. https://doi.org/10.1177/19476035231222251

11. Aussieker T et al. Collagen Protein Ingestion Does Not Stimulate Myofibrillar or Connective Tissue Protein Synthesis Rates Following Exercise. Med Sci Sports Exerc, 2025. https://doi.org/10.1249/MSS.0000000000003492

12. Rajan S. Response to Myung et al. regarding oral collagen supplementation. Am J Med, 2025. https://doi.org/10.1016/j.amjmed.2025.01.018

13. Collagen Stewardship Alliance (CSA). Response to Myung et al. systematic review. 2025.

14. GROW Coalition. Response to Myung et al. systematic review. 2025.

15. Proksch E et al. Oral supplementation of specific collagen peptides has beneficial effects on human skin physiology: a double-blind, placebo-controlled study. Skin Pharmacol Physiol, 2014;27(1):47-55. https://doi.org/10.1159/000351376

16. Proksch E, Segger D et al. Oral intake of specific bioactive collagen peptides reduces skin wrinkles and increases dermal matrix synthesis. Skin Pharmacol Physiol, 2014;27(3):113-9. https://doi.org/10.1159/000355523

17. Proksch E et al. Oral Supplementation of Specific Bioactive Collagen Peptides Improves Skin Hydration and Reduces Wrinkles. Cosmetics, 2025. https://doi.org/10.3390/cosmetics12010023

18. Schunck M et al. Dietary supplementation with specific collagen peptides has a body mass index-dependent beneficial effect on cellulite morphology. J Med Food, 2015;18(12):1340-8. https://doi.org/10.1089/jmf.2015.0022

19. Sangsuwan W et al. Effect of oral collagen hydrolysate on skin elasticity in postmenopausal women. J Dermatolog Treat, 2020. https://doi.org/10.1080/09546634.2020.1764906

20. Kim DU et al. Oral Intake of Low-Molecular-Weight Collagen Peptide Improves Hydration, Elasticity, and Wrinkling in Human Skin. J Med Food, 2022. https://doi.org/10.1089/jmf.2022.0039

22. Hwang SB et al. Oral Intake of Low-Molecular-Weight Collagen Peptide Improves Cellulite and Hair Thickness in Women. J Med Food, 2026.

25. Choi SY et al. Effects of collagen tripeptide supplement on skin properties. J Cosmet Laser Ther, 2014. https://doi.org/10.3109/14764172.2013.854119

26. Pogacnik T et al. Fish collagen supplementation with methylsulfonylmethane and vitamin C: randomized double-blind placebo-controlled study. J Funct Foods, 2023. https://doi.org/10.1016/j.jff.2023.105756

27. Vleminckx H et al. Effects of Oral Collagen Supplementation on Skin Properties: A Randomized, Double-Blind, Placebo-Controlled Study. J Cosmet Dermatol, 2024. https://doi.org/10.1111/jocd.16313

29. Kalman DS et al. A Randomized Double-Blind Placebo-Controlled Study of Eggshell Membrane Hydrolysate on Skin, Hair, and Nail Quality. J Cosmet Dermatol, 2020. https://doi.org/10.1111/jocd.13154

30. Hexsel D et al. Oral supplementation with specific bioactive collagen peptides improves nail growth and reduces symptoms of brittle nails. J Cosmet Dermatol, 2017. https://doi.org/10.1111/jocd.12393

32. Crowley DC et al. Safety and efficacy of undenatured type II collagen in the treatment of osteoarthritis of the knee: a clinical trial. Int J Med Sci, 2009;6(6):312-21. https://doi.org/10.7150/ijms.6.312

33. Lugo JP et al. Undenatured type II collagen (UC-II) for joint support. Nutr J, 2016;15:14. https://doi.org/10.1186/s12937-016-0130-8

34. Yuenyongviwat V et al. Efficacy and Safety of Undenatured Type II Collagen Combined with Hydrolyzed Collagen for Knee Osteoarthritis. Sci Rep, 2025. https://doi.org/10.1038/s41598-025-87521-3

36. Bruyere O et al. Effect of collagen hydrolysate in articular pain. Comp Ther Med, 2012;20(3):124-30. https://doi.org/10.1016/j.ctim.2011.12.007

40. Bongers C et al. Collagen peptide supplementation does not reduce knee pain or improve knee function. Appl Physiol Nutr Metab, 2020. https://doi.org/10.1139/apnm-2019-0730

42. Eskiyurt N et al. Efficacy and Safety of Natural Eggshell Membrane (NEM) in Patients with Grade I/II Knee Osteoarthritis. J Arthritis, 2019.

43. Park SJ et al. Eggshell membrane supplementation for knee osteoarthritis: A randomized, double-blind, placebo-controlled study. J Funct Food, 2024. https://doi.org/10.1016/j.jff.2024.106176

46. König D et al. Specific Collagen Peptides Improve Bone Mineral Density and Bone Markers in Postmenopausal Women. Nutrients, 2018;10(1):97. https://doi.org/10.3390/nu10010097

47. Zdzieblik D et al. Long-term collagen peptide supplementation and bone mineral density. J Bone Metab, 2021. https://doi.org/10.11005/jbm.2021.28.2.101

48. Devasia S et al. Fish-derived collagen peptides for type 2 diabetes: A randomized controlled trial. J Diabetes Metab, 2020. https://doi.org/10.35248/2155-6156.20.11.853

49. Zhu CF et al. Treatment with Marine Collagen Peptides Modulates Glucose and Lipid Metabolism in Chinese Patients with Type 2 Diabetes Mellitus. Am J Med Sci, 2010;340(5):360-6. https://doi.org/10.1097/MAJ.0b013e3181eaaf4e

50. Hatanaka T et al. Identification of DPP-IV inhibitory activity in collagen hydrolysates. J Enzyme Inhib Med Chem, 2014;29(6):823-8. https://doi.org/10.3109/14756366.2013.855207

51. Zdzieblik D et al. Collagen peptide supplementation improves body composition and increases muscle strength in elderly sarcopenic men. Br J Nutr, 2015;114(8):1237-45. https://doi.org/10.1017/S0007114515002810

52. Nulty C et al. Effects of Hydrolyzed Collagen Supplementation on Muscle Strength and Tendon Properties in Recreationally Active Men. Eur J Sport Sci, 2025. https://doi.org/10.1002/ejsc.12237

53. Lee SK et al. Pressure ulcer healing with a concentrated, fortified, collagen protein hydrolysate supplement. Adv Skin Wound Care, 2006. https://doi.org/10.1097/00129334-200603000-00011

54. Sugihara F et al. Clinical Effects of Ingesting Collagen Hydrolysate on Facial Skin Properties. Sci Rep, 2018.

55. Yamanaka H et al. Effects of collagen peptide supplementation on the healing of pressure ulcers. J Nutr Intermed Metab, 2017.

56. Miyab MF et al. Effect of a Nutritional Supplement Containing Collagen Peptides on Burn Wound Healing. Burns, 2020. https://doi.org/10.1016/j.burns.2020.04.026

58. Dressler P et al. Improvement of Functional Ankle Properties Following Supplementation with Specific Collagen Peptides in Athletes with Chronic Ankle Instability. J Sports Sci Med, 2018. https://pubmed.ncbi.nlm.nih.gov/29769831/

59. Praet SF 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. https://doi.org/10.3390/nu11010076

61. Kuwaba K et al. Fish-Derived Collagen Peptides Improve Fatigue and Mood States. J Diet Suppl, 2024. https://doi.org/10.1080/19390211.2024.2306488

62. Vijven JPJ et al. Symptomatic and chondroprotective treatment with collagen derivatives in osteoarthritis: a systematic review. Osteoarthritis Cartilage, 2012. https://doi.org/10.1016/j.joca.2012.04.008

63. Zhang Y et al. Oral administration of type II collagen suppresses inflammatory arthritis in mice and rheumatoid arthritis in humans. Arthritis Rheum, 2008. https://pubmed.ncbi.nlm.nih.gov/18240258/

64. Barnett ML et al. Treatment of rheumatoid arthritis with oral type II collagen. Arthritis Rheum, 1998;41(2):290-7.

65. Kalic T et al. Collagen — An Important Fish Allergen for Improved Diagnosis. J Allergy Clin Immunol, 2020. https://doi.org/10.1016/j.jaip.2020.04.063

66. Knight J et al. Hydroxyproline ingestion and urinary oxalate excretion. Kidney Int, 2008;70(11):1929-34. https://doi.org/10.1038/sj.ki.5001906

67. Delgado PL et al. Serotonin function and the mechanism of antidepressant action. Arch Gen Psychiatry, 1990;47(5):411-8.

68. Paul C et al. Significant Amounts of Functional Collagen Peptides Can Be Incorporated in the Diet While Maintaining Indispensable Amino Acid Balance. Nutrients, 2019;11(5):1079. https://doi.org/10.3390/nu11051079

69. FDA. 21 CFR Parts 189 and 700. Bovine-derived materials; safety requirements.

70. Lu P et al. Extracellular Matrix Degradation and Remodeling in Development and Disease. J Cell Biol, 2012;196(4):395-406. https://doi.org/10.1083/jcb.201109110

71. Eastell R. Treatment of Postmenopausal Osteoporosis. 2007.

72. Seibel MJ. Biochemical markers of bone turnover. Clin Biochem Rev, 2005;26(4):97-122. https://pubmed.ncbi.nlm.nih.gov/16648882/

73. Ruff KJ et al. Eggshell membrane and fish oil for exercise-induced joint pain. Int J Phys Med Rehabil, 2020.

74. Hsu TF et al. Oral Hyaluronan Relieves Wrinkles and Improves Dry Skin. Nutrients, 2021;13(7):2220. https://doi.org/10.3390/nu13072220