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Key takeaways
● Skin: meta-analyses show small-to-moderate improvements in hydration and elasticity at 2.5–10 g/day over 8–12 weeks (1,2). A 2025 stratified analysis found the effect largely disappears in industry-independent, high-quality trials (3).
● Joints: meta-analyses report meaningful pain relief in knee osteoarthritis (standardised mean difference −0.58 across four RCTs, n=507) (4). All included trials rated high risk of bias.
● Bones: one well-conducted 12-month RCT showed bone mineral density gains at just 5 g/day in postmenopausal women (5). The evidence base is narrow — mostly one research programme.
● Muscle: collagen is an incomplete protein and lost head-to-head to whey in a leucine-matched trial (6). Useful for tendon adjunct; not a substitute for a complete protein.
● Safety: generally well tolerated. Two caveats: calcium-oxalate kidney stones (hydroxyproline metabolism raises urinary oxalate) (7) and levothyroxine / bisphosphonate spacing (protein-meal interactions).
Quick answer
Hydrolysed collagen peptides are a form of collagen protein enzymatically broken down into small peptide chains that absorb into the bloodstream. Randomised trials show modest, real improvements in skin, joint, and bone outcomes at doses of 2.5–15 g/day, with effects that build over weeks to months. The evidence is strongest for skin and knee osteoarthritis, promising for postmenopausal bone, and honest-to-modest elsewhere. Read on for the indication-by-indication evidence, the dose that matches your goal, and the safety caveats every top search result omits.
What are hydrolysed collagen peptides?
Collagen is the most abundant protein in the human body. It forms the structural scaffold of skin, tendon, ligament, cartilage, bone matrix, and blood vessels — roughly 30% of your total protein mass. In its native form, collagen exists as a triple helix of very large molecules (roughly 285–300 kilodaltons, or kDa) — far too large to be absorbed intact from the digestive tract (8).
Hydrolysed collagen peptides are what you get when you take native collagen — usually from bovine hide, marine skin and scales, or porcine tissue — and use enzymes to break the long protein chains into short peptide fragments, typically 3–6 kDa in molecular weight (8). The result is a soluble, flavour-neutral, white-to-cream powder that dissolves in hot or cold liquids. This is what supplement brands sell.
Two things about the terminology are worth clearing up early. First, "hydrolysed collagen" and "collagen peptides" refer to the same thing. The industry uses both terms interchangeably. We cover the terminology in depth in our full article on hydrolysed collagen versus collagen peptides. Second, "hydrolysed" and "hydrolyzed" are just British and American spellings of the same word.
For the full mechanistic explanation of how collagen is hydrolysed and why it matters for absorption, see our dedicated article on the process. Below, we focus on what happens once you swallow the powder.
How the body actually uses them
The intuitive story — you eat collagen, it becomes your collagen — is not quite right, and getting it right matters because it explains why the effects are modest and why doses higher than about 10 g/day rarely deliver more benefit.
Most of the collagen you swallow is digested to individual amino acids in the small intestine, joining the general amino-acid pool your body uses to build any protein it needs. This portion contributes glycine, proline, and hydroxyproline to your daily amino-acid intake. It is useful but nutritionally unremarkable.
What makes collagen peptides distinctive is a small biologically active fraction that survives intestinal digestion intact — chiefly two short peptides called Pro-Hyp (proline-hydroxyproline) and Hyp-Gly (hydroxyproline-glycine). Because hydroxyproline is rare in ordinary dietary protein, these dipeptides resist the enzymes that would normally chop them up (9). They cross into the bloodstream, where they can be measured 1–2 hours after a 5–10 g oral dose and persist for several hours (9,10).
This bioactive fraction is small — probably 1–3% of the ingested dose, meaning perhaps 100–300 milligrams of intact signalling peptides reach circulation from a 10 g scoop. But that fraction does the interesting biological work: it acts as a signal to fibroblasts (skin cells), chondrocytes (cartilage cells), and osteoblasts (bone-building cells), telling them to synthesise more of their local structural proteins.
The signalling framing predicts the trial data well. It explains why doubling the dose from 5 g to 10 g does not double the effect — the signalling fraction plateaus. It explains why a modest 5 g dose delivered measurable bone gains over 12 months in postmenopausal women (5). And it explains why collagen is a poor primary protein for muscle building — the muscle-protein signalling pathway is driven by leucine, which collagen contains in very low amounts.
Plasma pharmacokinetics reinforce the picture. After a 5–10 g oral dose, Pro-Hyp levels in blood peak within one to two hours and remain detectable for four to six hours (9,10). The area under the plasma concentration curve scales roughly linearly up to about 10 g and plateaus thereafter — meaning very high doses do not deliver proportionally more signal. This is the reason the trial evidence base clusters around 5–15 g/day, not higher.
What the evidence actually shows
What follows is the honest state of the evidence — meta-analyses named, effect sizes stated, and — where relevant — the funding-source caveat that top-ranking consumer articles skip. For a more skeptical read that pressure-tests every claim, see our dedicated article on whether hydrolysed collagen actually works.
Skin — the best-studied indication
There are now roughly two dozen randomised trials of hydrolysed collagen for skin outcomes, and several meta-analyses. The consistent finding: modest, statistically significant improvements in skin hydration, elasticity, and wrinkle depth at doses of 2.5–10 g/day over 8–12 weeks. The 2021 de Miranda meta-analysis (19 RCTs, n=1,125) reported favourable effects across multiple skin parameters (1). The 2023 Pu meta-analysis (26 RCTs, n=1,721) corroborated this with strong statistical signals for both hydration and elasticity (2).
Here is the finding that changes the picture. In 2025, a stratified meta-analysis published in the American Journal of Medicine (23 RCTs, n=1,474) split the trials by funding source and methodological quality (3). The pooled effect was significant overall — but in the subgroup of trials not funded by the collagen industry, and in the subgroup of high-quality studies, the effect on hydration, elasticity, and wrinkles was no longer statistically significant. In other words, the headline meta-analytic estimates that everyone quotes are inflated by industry-funded, lower-quality work.
This does not mean the effect is zero. It means the effect is smaller than the marketing suggests. Reasonably typical results: a modest improvement in the skin's ability to retain moisture (measured by corneometry), a small increase in cutometer-measured elasticity, and a modest reduction in wrinkle depth on standardised photography — most trials report effect sizes in the 5–15% range on these outcomes, not the transformative changes shown in advertising imagery.
A representative recent trial: the CollaSel Pro 2024 study (112 healthy women, 10 g/day for 8 weeks, industry-funded) reported statistically significant improvements in skin elasticity, hydration, and roughness (15). A typical modern trial in the category — a small-to-moderate real effect over eight weeks, with the funding-source caveat that applies to most of the literature. The full skin article goes deeper into the individual trials and what to reasonably expect.
Joints — knee osteoarthritis pain
The Yu 2023 meta-analysis (4 RCTs, n=507) is the load-bearing evidence for joints (4). It reported a standardised mean difference of −0.58 for knee osteoarthritis pain (95% CI −0.98 to −0.18, p=0.004) — meaningfully above the −0.37 minimum clinically important difference. Adverse events were not different from placebo. The 2024 García-Coronado trial-sequential meta-analysis (35 RCTs, n=3,165) confirmed the direction of effect across a much larger evidence base (11).
Two caveats. All four trials in the Yu 2023 analysis were rated high risk of bias. Most included trials ran three to six months — long enough to demonstrate benefit but not long enough to compare against the multi-year evidence base for exercise and weight management, which remain the largest levers for knee osteoarthritis.
A useful mechanistic note: the collagen in hydrolysed collagen supplements is Type I and Type III (skin, tendon, bone matrix). Articular cartilage is Type II. The joint-pain benefit is chondrocyte signalling by peptide fragments that happen to reach the joint tissue — not direct incorporation. A different class of product — undenatured Type II collagen, or UC-II — works via oral tolerance at Peyer's patches at a much smaller ~40 mg dose. See the full joints article for the population breakdown.
Bones — the most interesting result in the literature
For postmenopausal women, the anchor trial is König 2018 (5). Design: 131 postmenopausal women with reduced bone mineral density (T-score ≤ −1); randomised to 5 g/day of specific collagen peptides or matched maltodextrin placebo; 12 months of supplementation. Result: statistically significant increases in BMD at the lumbar spine and femoral neck versus placebo, with favourable shifts in P1NP (formation marker) and CTX-1 (resorption marker). A four-year open-label follow-up reported progressive gains.
The dose is worth noting: 5 g/day was enough. Higher doses have not been shown to produce more effect for bone. This is one indication where the marketing pressure toward 10-g scoops is not evidence-aligned. The caveat: most of the bone literature funnels through the Freiburg research group and Gelita-funded work. Independent replication is limited. The full bones article covers the evidence in depth — and is clear that collagen is not a substitute for prescribed osteoporosis therapy in diagnosed disease.
Muscle recovery and sarcopenia — the honest version
This is where marketing most diverges from science. Collagen is an incomplete protein: it contains no tryptophan at all, and roughly one-third the leucine of whey. Leucine is the amino acid that triggers muscle protein synthesis. So collagen is a structurally poor tool for building or preserving muscle.
The most direct test was Oikawa 2020: a 10-week head-to-head comparison of whey versus leucine-matched collagen peptides in young adults doing supervised resistance training (6). Muscle thickness gains were greater in the whey group — even though the leucine content was equalised. The likely reason: the whey serving delivered ~13.9 g of essential amino acids; collagen delivered ~7.7 g — below the threshold for maximal muscle protein synthesis stimulation.
The Zdzieblik 2015 trial in elderly sarcopenic men reported striking gains in lean mass at 15 g/day of collagen combined with resistance training (12). But the reported effect sizes were large enough that a published critique in the same journal questioned reproducibility. They have not been clearly replicated by independent groups.
The honest position: if muscle is your goal, take whey (or a complete plant blend) as your primary protein and add collagen as an adjunct for tendon and joint support. Pre-exercise timing (roughly one hour before training) with vitamin C has modest evidence for tendon collagen synthesis (13). See the full muscle-recovery article and the direct whey comparison.
Hair, nails, and gut health — the weaker claims
A small number of trials — mostly industry-funded, mostly self-reported — report improvements in hair thickness and nail strength (14). The biological story (collagen provides amino acid substrate for keratin) is plausible but indirect. Treat any visible hair or nail effect as a bonus, not the reason to buy. Our hair and nails article covers this honestly.
Gut health is a common marketing claim and the weakest link in the evidence chain. The proposed mechanisms — glycine and glutamine supporting the mucosal barrier — do not have collagen-specific human data behind them. There is a small, mostly extrapolative literature. Read our gut health article for the honest treatment.
How hydrolysed collagen compares to gelatin, bone broth, and UC-II
The category "collagen" is broader than the peptide supplements this article focuses on. Four other forms come up regularly in reader questions — and understanding the distinctions is useful because the trial evidence maps to specific forms, not to "collagen" as a general category.
Gelatin
Gelatin is collagen that has been partially denatured — the triple helix broken but the peptide chains still relatively long (typically 20–250 kDa) compared to hydrolysed collagen peptides (3–6 kDa). Gelatin gels when it cools; hydrolysed collagen does not. Trial evidence for gelatin as a supplement is thinner than for hydrolysed peptides. Shaw 2017 used gelatin plus vitamin C for the tendon-synthesis marker study (13) — an interesting exception where gelatin performed well.
Bone broth
Bone broth is dietary collagen — a whole-food source that provides collagen, gelatin, and general amino acids in a matrix with other minerals. A typical cup of well-made bone broth contains roughly 0.6–1.0 g of collagen (8). To match a 10 g supplement scoop you would need approximately 10–17 cups daily. Bone broth is a legitimate culinary food; it is not a practical substitute for supplement dosing. Our gelatin and bone broth comparison article covers the numbers in more detail.
Undenatured Type II collagen (UC-II)
UC-II is a completely different product with a completely different mechanism. It is undenatured Type II cartilage collagen taken at approximately 40 mg per day (three orders of magnitude smaller than hydrolysed collagen doses). The mechanism is not amino-acid provision or peptide signalling — it is oral tolerance induction, in which small amounts of Type II collagen presented to the immune system at Peyer's patches modulate T-cell responses against joint cartilage. UC-II has independent trial evidence for knee osteoarthritis and is a reasonable alternative for joint-specific goals.
How much to take — the indication-anchored dose
There is no single "correct" dose of collagen peptides. What you should take depends on what you are trying to achieve.
|
Indication |
Dose |
Duration |
Anchor trial |
|
Skin (hydration, elasticity) |
2.5–10 g/day |
8–12 weeks |
de Miranda 2021 meta-analysis (1); Pu 2023 meta-analysis (2) |
|
Bone (postmenopausal) |
5 g/day |
12 months |
König 2018 (5) |
|
Knee OA pain |
10 g/day |
3–6 months |
Yu 2023 meta-analysis (4) |
|
Tendon / recovery |
10–15 g/day |
8–12 weeks |
Shaw 2017 tendon-synthesis markers (13) |
|
Sarcopenia (with training) |
15 g/day |
12 weeks |
Zdzieblik 2015 — see caveats (12) |
10 g/day is not universally better than 5 g. For postmenopausal bone, 5 g is the trial-validated dose and higher doses have not been shown to add benefit. For skin, both 2.5 g and 10 g have positive trials. If bone is your goal, 5 g is enough and cheaper. If joints or muscle are your goals, 10 g or 15 g respectively is closer to trial protocols.
Above 15 g/day there is no evidence advantage and the theoretical oxalate load rises proportionally. For a deeper treatment including split-dose vs single-dose, timing, and format, see our full dosage article.
How to use it — timing, mixing, and consistency
The mechanistic story — signalling by bioactive dipeptides that reach the bloodstream within hours — informs the practical answers here. Most timing questions have less consequential answers than the internet suggests.
With food or on an empty stomach
Both work. The Pro-Hyp and Hyp-Gly dipeptides survive intestinal hydrolysis whether the dose is taken fasting or with a meal.
Hot or cold
Collagen peptides are heat-stable below approximately 80°C. Mixing into hot coffee or tea does not degrade the bioactive fraction.
Split or single dose
Both work. A single 10 g serving and a split 5 g morning + 5 g evening produce broadly similar plasma peptide profiles. Consistency of daily intake matters more than within-day timing.
Vitamin C — useful if dietary intake is low
Vitamin C is a required cofactor for prolyl hydroxylase. If your diet already includes citrus, peppers, berries, or broccoli daily, supplemental vitamin C is not load-bearing. The full stacking article covers this in detail.
Post-exercise timing for tendon — a small evidence advantage
For tendon and ligament specifically, Shaw 2017 reported that collagen taken with vitamin C one hour before resistance training increased circulating markers of collagen synthesis (13). For skin or bone, timing appears irrelevant. Our timing article covers this in more depth.
How long until you notice anything
Skin and joint trials typically show measurable changes at 8–12 weeks of consistent daily supplementation. Bone benefits, based on König 2018, require the full 12 months. The honest answer to "how long?" is: give it three months at minimum before assessing whether you notice anything, and 12 months if bone is your specific goal.
Safety and who should be cautious
Hydrolysed collagen has a good general safety profile. Minor side effects — mild gastrointestinal fullness, unpleasant taste, occasional bloating — occur in some people but are typically transient. The side effects article covers the full range. Three caveats deserve explicit attention because top-ranking consumer articles routinely omit them.
Kidney stones — the oxalate consideration
Collagen is exceptionally high in hydroxyproline. In the liver, hydroxyproline is metabolised to glyoxylate and then to oxalate. In healthy kidneys this is inconsequential. But in people with a personal history of calcium-oxalate kidney stones, this is one of the few supplements where a real metabolic concern exists. Knight and colleagues reported in 2006 that a 30 g gelatin dose increased urinary oxalate excretion by approximately 43% (7).
This does not mean people with a stone history cannot take collagen — it means they should discuss it with their nephrologist and take practical steps: keep the daily dose at 5 g, take calcium-containing food or supplements with the dose (which binds dietary oxalate in the gut), and maintain generous hydration. Our kidney stones article walks through the specifics.
Pregnancy and lactation — default to caution
There are no specific clinical trials of collagen peptide supplementation in pregnancy or lactation. Collagen is a food-grade animal protein consumed routinely in cooked meat and broths, so the absolute risk is presumably low. The responsible position is to discuss with your obstetrician before adding any non-essential supplement during pregnancy or breastfeeding. See our pregnancy article.
Medications with timing-sensitive absorption
Collagen at 10 g/day is a meaningful protein load. Protein meals reduce levothyroxine absorption — take collagen and thyroid medication at different times (30–60 minute separation is enough). Oral bisphosphonates (alendronate, risedronate) must be taken on an empty stomach 30–60 minutes before any food or drink other than plain water — do not take collagen in this window. Similar timing applies to tetracycline antibiotics.
How to choose a product
The category is crowded and marketing is largely undifferentiated. Rather than recommending specific products, here are the criteria a careful buyer should apply — in decreasing order of importance.
Third-party certificate of analysis
Collagen is a category where third-party heavy-metals testing matters. Independent testing programmes (ConsumerLab, the Clean Label Project) have found measurable lead, cadmium, mercury, and arsenic in some collagen brands. A batch-specific Certificate of Analysis from an ISO/IEC 17025-accredited laboratory, published or available on request, is the single most useful signal of quality.
Peptide molecular weight
Peptides in the 2–3 kDa range appear to absorb somewhat better than larger 5-kDa peptides (16). Quality manufacturers publish or provide this on request. If the label is silent, that is a small red flag.
Source transparency
Bovine, marine, and porcine are all legitimate sources. The 2023 Pu meta-analysis found no significant difference between sources in skin outcomes (2). What matters is that the source is disclosed and, ideally, that welfare or sustainability standards are stated. See our marine vs bovine article for source-by-source detail.
Type I and III versus Type II
Almost all hydrolysed collagen supplements are Type I and III — the collagen of skin, tendon, bone matrix, and vasculature. Type II is the collagen of joint cartilage, and Type II supplements exist as a separate UC-II category at ~40 mg doses. For general skin, joint, and bone support, Type I and III is what you want.
Serving size and cost per gram
The relevant comparison is not price per tub but price per gram of collagen delivered at your target daily dose. Our buyer's-guide article walks through the criteria-first framework in more depth.
Who this is reasonable for — and who it is not
Reasonable candidates
● Adults aged 40 and above concerned about skin ageing — the modest but real hydration and elasticity effects can complement sun protection and topical retinoids.
● Adults with symptomatic knee osteoarthritis, particularly those with cardiovascular or gastrointestinal contraindications to chronic NSAID use.
● Postmenopausal women with osteopenia or early osteoporosis, as an adjunct to standard care. Take 5 g/day.
● Athletes in tendon-heavy sports using collagen at 10–15 g/day timed around training as a connective-tissue adjunct alongside a complete-protein diet.
Where the picture is more mixed
● People taking it primarily for hair or nail outcomes. The evidence is weak.
● People taking it primarily for gut health. The evidence is largely extrapolative.
● Young adults primarily interested in muscle building. Collagen is a poor tool for this purpose. Use a complete protein.
Where honest advice is to avoid or defer
● Anyone with a personal history of calcium-oxalate kidney stones should discuss with a nephrologist before starting.
● Pregnant and breastfeeding women should default to caution and discuss with their obstetrician.
● Vegans and vegetarians — no functionally equivalent vegan product exists; see the alternatives article for the honest treatment.
● Anyone using collagen as a substitute for prescribed osteoporosis therapy. It is an adjunct, not a replacement.
What we still don't know
● How large is the true skin effect in industry-independent, high-quality trials? The 2025 stratified meta-analysis suggests the effect may be small or absent once confounders are controlled (3).
● Does the bone effect replicate outside the Freiburg research programme? The König 2018 result is striking. It has not been broadly replicated by independent groups.
● What is the long-term efficacy signal? Most trials run 8–24 weeks. There is essentially no evidence base beyond 12 months.
● Which molecular-weight fraction is most bioactive? Whether specific dipeptide ratios matter more than average MW is not settled.
● Is the sarcopenia signal from Zdzieblik 2015 real and reproducible? The magnitude has not been clearly replicated by independent groups.
● What happens in kidney stone formers on chronic supplementation? The acute-dose oxalate data support concern; long-term data are absent.
Bottom line
Hydrolysed collagen peptides are a legitimate but modestly-effective supplement across skin, joints, and bones — with the honest caveat that the skin evidence attenuates in independent high-quality trials, the bone evidence is narrow, and collagen is a poor tool for muscle building. Take 5 g/day if bone is your goal, 10 g/day if joints or skin are your goal, and 10–15 g/day if tendon or recovery is your goal. Expect measurable but modest change over 8–12 weeks, and pair it with the larger lifestyle levers — sun protection for skin, weight management and exercise for joints, vitamin D and calcium and weight-bearing exercise for bones. Speak to a clinician if you have a history of calcium-oxalate kidney stones, are pregnant or breastfeeding, or take thyroid medication or bisphosphonates.
Frequently asked questions
Are collagen peptides the same as hydrolysed collagen?
Yes. The two terms describe the same product. See our full comparison article for the deeper explanation.
How much hydrolysed collagen should I take per day?
It depends on your goal. For postmenopausal bone, 5 g/day (König 2018). For skin, 2.5–10 g/day. For knee OA pain, 10 g/day. For tendon recovery or sarcopenia, 10–15 g/day. Above 15 g/day there is no evidence advantage. Full detail in the dosage article.
When is the best time to take it?
For skin, joints, and bones, timing does not appear to matter. For tendon recovery specifically, there is modest evidence that taking collagen with vitamin C about one hour before resistance training may be advantageous. See the timing article.
Does hydrolysed collagen actually work?
For skin, joints, and postmenopausal bone: yes, at modest effect sizes. For muscle building: not really. For hair, nails, and gut health: the evidence is weaker. Our full evidence review is the deep treatment.
Is it safe during pregnancy?
There are no specific pregnancy trials. The responsible answer is to discuss with your obstetrician. See the pregnancy article.
What are the side effects?
Generally well tolerated. Common: mild gastrointestinal fullness, occasional bloating. Specific caveat: in people with calcium-oxalate kidney stones, hydroxyproline metabolism raises urinary oxalate. See the side effects article and the kidney stones article.
Marine, bovine, or porcine — which is best?
The 2023 Pu meta-analysis found no significant difference for skin outcomes. Choose based on ethical, allergen, or preference reasons. Detail in the source comparison article.
Is collagen as good as whey for muscle?
No. Collagen is an incomplete protein. In a 10-week leucine-matched trial, whey still produced greater muscle thickness gains. See the full whey comparison article.
Can I take it with coffee?
Yes. Collagen peptides are heat-stable at typical drinking temperatures.
References
1. de Miranda RB, Weimer P, Rossi RC. Effects of hydrolyzed collagen supplementation on skin aging: a systematic review and meta-analysis. Int J Dermatol 2021. https://pubmed.ncbi.nlm.nih.gov/34553487/
2. 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
3. Lee SH, Kim Y, Han SH, et al.. Effects of collagen supplements on skin aging: a systematic review and meta-analysis of RCTs. Am J Med 2025. https://doi.org/10.1016/j.amjmed.2025.03.018
4. Yu Y, Cheng K, Zhao W, et al.. Analgesic efficacy of collagen peptide in knee osteoarthritis: a meta-analysis of RCTs. J Orthop Surg Res 2023. https://pubmed.ncbi.nlm.nih.gov/37715244/
5. König D, Oesser S, Scharla S, Zdzieblik D, Gollhofer A. Specific collagen peptides improve bone mineral density and bone markers in postmenopausal women — a randomized controlled study. Nutrients 2018. https://pubmed.ncbi.nlm.nih.gov/29337906/
6. Oikawa SY, Holloway TM, Phillips SM, 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 2020. https://doi.org/10.1123/ijsnem.2019-0319
7. Knight J, Jiang J, Assimos DG, Holmes RP. Hydroxyproline ingestion and urinary oxalate and glycolate excretion. Kidney Int 2006. https://pubmed.ncbi.nlm.nih.gov/16988700/
8. León-López A, Morales-Peñaloza A, Martínez-Juárez VM, et al.. Hydrolyzed collagen — sources and applications. Molecules 2019. https://pmc.ncbi.nlm.nih.gov/articles/PMC6891674/
9. Iwai K, Hasegawa T, Taguchi Y, et al.. Identification of food-derived collagen peptides in human blood after oral ingestion of gelatin hydrolysates. J Agric Food Chem 2005. https://pubmed.ncbi.nlm.nih.gov/16076145/
10. Shigemura Y, Kubomura D, Sato Y, Sato K. Dose-dependent changes in the levels of free and peptide forms of hydroxyproline in human plasma after collagen hydrolysate ingestion. Food Chem 2014. https://pubmed.ncbi.nlm.nih.gov/24054241/
11. García-Coronado JM, et al.. Effect of collagen supplementation on osteoarthritis symptoms: a meta-analysis. Osteoarthr Cartil 2024. https://doi.org/10.1016/j.joca.2024.01.005
12. Zdzieblik D, Oesser S, Baumstark MW, Gollhofer A, König D. Collagen peptide supplementation in combination with resistance training improves body composition and increases muscle strength in elderly sarcopenic men. Br J Nutr 2015. https://pubmed.ncbi.nlm.nih.gov/26353786/
13. Shaw G, Lee-Barthel A, Ross ML, Wang B, Baar K. Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. Am J Clin Nutr 2017. https://pubmed.ncbi.nlm.nih.gov/27852613/
14. Hexsel D, Zague V, Schunck M, et al.. Oral supplementation with specific bioactive collagen peptides improves nail growth. J Cosmet Dermatol 2017. https://pubmed.ncbi.nlm.nih.gov/28786550/
15. Various authors. CollaSel Pro RCT — safety and efficacy of hydrolyzed collagen peptide supplementation in adult females. J Clin Med 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC11432272/
16. Multiple authors. Effects of collagen peptides as a dietary supplement on muscle damage recovery and fatigue responses. Nutrients 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC11478671/