What It Is and Does It Work? 

Collagen protein supplements do not appear to do much for muscle, tendons, pain, or skin. As a protein, collagen is missing one of the nine essential amino acids, and no trial comparing it directly with whey has found collagen ahead for building muscle. For tendons and pain, most data show little to no benefit compared to placebo. For skin, the small gains show up on measuring devices in trials mostly run or paid for by collagen companies, and no trial has shown a difference you could see in the mirror.

Collagen protein is sold as a fix for everything from sore knees to wrinkles, and global sales of collagen supplements more than doubled from 2018 to 2020, to about 8.4 billion US dollars.¹ While it is very popular, it mostly doesn’t live up to the hype for the things it’s said to do. Mechanistically, collagen protein is said to supply the building blocks your body uses to make its own collagen, so eating it should build more in your tendons, joints, and skin. The problem is what happens after you swallow it. Digestion breaks collagen into amino acids and small fragments that join the same pool as every other protein you eat, and as far as we can find, no study has shown those fragments arriving in human skin or tendon.² Where collagen has looked best, the comparison was usually a placebo with no protein in it, which shows that adding protein to the diet helps, something that any protein would do.³ Counted toward your daily protein target, collagen is fine. As a treatment for tendons, joints, or skin, the evidence doesn’t support it.

• Collagen is an incomplete protein, with no tryptophan and about a third of the leucine in whey.
• Collagen counts toward your daily protein when the rest of your diet covers what it’s missing.
• The 2026 analysis that ranked collagen above whey rested on two small trials that used a placebo with no Calories.
• Training increases connective tissue rebuilding, and collagen hasn’t been shown to add to it.
• Collagen’s average effect on joint pain is below the smallest change people typically notice.
• Skin trials show small changes in device readings, mostly in company-funded studies, and none has shown a visible difference.

What Is Collagen, and What Does It Do in the Body?

Collagen is the most common structuralprotein in the human body, making up about 25% of the body’s total protein content. Its primary role is to provide structural support to connective tissues like ligaments, tendons, bone, cartilage, and skin, though it is found in virtually every tissue, including teeth, eyes, blood vessels, and more. There are at least 27 different types of collagen in the human body, but types I, II, III, and IV are the most abundant in muscles, joints, and skin. ⁴ 

Normal collagen production and regulation are essential for health. Diseases like scurvy, osteogenesis imperfecta (also called brittle bone disease), and Ehlers-Danlos syndrome (a genetic disorder affecting connective tissues), among many others, involve problems with collagen in the body or its synthesis.⁵ 

Changes in how the body creates and maintains collagen affect the appearance and functioning of various tissues. The loss or degeneration of collagen in the skin reduces elasticity and promotes the development of wrinkles. Reduced or altered collagen content in tendons and ligaments may be associated with joint pain and other movement limitations. Anabolic steroids have been shown in some animal models to lead to tendons becoming stiffer and less flexible, thereby leading to a greater risk of failure. That hasn’t been shown directly in humans. Tendon ruptures are more common in anabolic steroid users, though, and testosterone therapy has been associated with higher odds of quadriceps tendon injury, so changes to the collagen in these tissues might be part of the cause.^{6, 7}

What is a collagen supplement?

A collagen supplement is collagen protein extracted from animal tissue, usually from cows, pigs, or marine sources such as fish skin and scales, and most products are hydrolyzed, meaning the protein has been broken into smaller pieces with water, heat, enzymes, or a combination of them.⁸ Hydrolyzed collagen and collagen peptides are two names for the same thing, while gelatin is collagen that has been only partly broken down. Other synthetic types of collagen are used in clinical applications and as food additives.

Is collagen safe to take?

Collagen supplements appear safe for most people when they are made under Current Good Manufacturing Practices (CGMP) and tested by a qualified third party for purity. Most of the published data on allergic reactions come from injected bovine collagen implants used in cosmetic dermatology rather than from oral supplements. ⁹ One case report described Creutzfeldt-Jakob disease, the human prion disease related to mad cow disease, suspected to have been acquired from gelatin capsules.¹⁰ The European Food Safety Authority’s 2020 assessment of prion risk from ruminant collagen and gelatin, which is written for animal feed, is the closest formal risk estimate available. Fortunately, it states that risk is very low for that use.¹¹ 

How much protein is in collagen powder?

The protein content in collagen powder varies by manufacturer, so the label is the place to check. Whey protein isolate is typically more than 90% protein by weight, while pea and soy protein isolates range from 77% to 81% and from 61% to 91%, respectively.¹² Protein by weight doesn’t tell you how useful a protein is, though, because it ignores how much of each essential amino acid the protein supplies. Essential amino acids are the ones the body can’t make and has to get from food.

Is collagen a complete protein?

No. Collagen contains no tryptophan, one of the nine essential amino acids, so it’s classed as an incomplete protein and scores 0 on the Protein Digestibility-Corrected Amino Acid Score (PDCAAS).¹³ PDCAAS is a measurement of protein quality, running from 0 (worst) to 1.0 (best). It compares a protein’s essential amino acids with a reference pattern, takes the one in shortest supply, and adjusts for how well people digest the protein. For reference, whey protein has a PDCAAS of 1.0.¹⁴ Compared to whey, collagen also carries far less leucine, the essential amino acid most closely tied to switching on muscle protein synthesis, the rate at which the body builds new muscle protein. In one training study, 35 grams of whey supplied about 3 grams of leucine, and 35 grams of collagen supplied about 1 gram.¹⁵ Reduced amounts of branched chain amino acids, essential amino acids, or both in a protein will often require someone to consume more of it or use other protein sources to ensure normal function. In the case of collagen protein, the reduced branched chain and essential amino acid content make it less useful for supporting muscle protein synthesis in the body. 

Does collagen count toward your daily protein intake?

Yes, collagen protein counts towards your daily protein intake. Collagen protein, like all other forms of protein, supplies amino acids. When it’s consumed alongside other protein that covers what it’s missing, it adds to the pool of amino acids the body builds from. A modeling study, two of whose three authors work for a collagen manufacturer and the Collagen Research Institute, calculated that collagen could replace up to 36% of the protein in a typical American diet before essential amino acid needs fell short.¹³On its own however, collagen doesn’t raise muscle protein synthesis. ^{16, 17}

How is collagen supposed to work?

Supplemental collagen protein is said to work by delivering a relatively high amount of the amino acids glycine and proline, two amino acids the body uses to build collagen. Supplemental collagen is rich in these amino acids, whereas whey, casein, egg, and beef protein are much lower. Glycine and proline aren’t essential amino acids, though. The body makes both, deficiencies from diet alone are rare, and a shortage of either is unlikely to be what limits collagen production.

Collagen also comes from ordinary food. Meat with connective tissue, animal skin, and bone broth all contain collagen, so most people who eat animal foods already get some. Egg whites and spirulina, a type of algae sold as a supplement, supply glycine and proline but contain no collagen.

Does eating collagen turn into collagen in your body?

Eating collagen does not turn directly turn into collagen in your body. Digestion breaks collagen down into amino acids and small peptides that join the same pool as amino acids from any other protein, and as far as we can find, no human study has shown those pieces being directed to a particular tissue.

What are collagen peptides like Pro-Hyp, and do they reach your tissues?

The newer proposed mechanism for collagen protein suggests that some hydrolyzed collagen survives digestion as two-amino-acid fragments, mainly prolyl-hydroxyproline (Pro-Hyp) and hydroxyprolyl-glycine (Hyp-Gly), which show up intact in the blood an hour or two after a dose, and go on to drive greater collagen production.²In Petri dishes, Pro-Hyp attracts fibroblasts, the cells that build collagen, and makes them multiply.¹⁸ These fragments are built around hydroxyproline, a modified amino acid found mostly in collagen and a few other proteins, although meat and animal skin supply some hydroxyproline too.^19,20

The trouble is translating findings between the lab and real life. In that experiment, mouse skin cells responded to these fragments at 200 nanomoles per milliliter, but the highest blood levels measured in people after a large dose were 20 to 60.^{18, 2} In rats given labeled Pro-Hyp, only about 5% of what reached the cartilage was still intact Pro-Hyp.²¹As far as we can find, no study has measured these fragments arriving in human skin or tendon. A plausible mechanism is a reason to run trials, but mechanisms don’t settle much on their own without solid outcome data.

Does collagen help build muscle?

Collagen protein does not appear to be beneficial for building muscle on its own because of its amino acid profile, which lacks tryptophan and is low in leucine. When compared to whey protein in this context, whey raises muscle protein synthesis compared to placebo whereas supplemental collagen does not.16,17 Humans typically eat a variety of proteins however, and in that context, collagen helps build muscle about the same as any extra protein does when compared to a non-protein placebo.

For example, a 2024 meta-analysis of 19 trials found that adding collagen produced small-to-moderate gains in fat-free mass and a small gain in strength compared with placebo.³ The placebo groups in those trials got no protein, so what the trials show is that adding protein to the diet helps if people are lifting weights, especially when total intake is below about 1.6 grams per kilogram a day.²²

Is collagen better than whey for building muscle?

Collagen protein isn’t better than whey protein for building muscle based on available evidence. In one direct comparison of the two in 22 untrained young adults lifting for 10 weeks, whey grew more muscle in the thighs and arms than collagen did, even though the researchers added 2 grams of leucine to the collagen so the two supplements were matched for this key amino acid.⁴In 97 untrained middle-aged men lifting for 12 weeks, the fat-free mass gains with collagen, whey, and placebo weren’t statistically different from one another in an exploratory comparison, with collagen numerically ahead; that trial was co-authored by the Collagen Research Institute.²³

Recently, a network meta-analysis ranked collagen first, above whey for building muscle. It credited collagen with about 7 pounds more fat-free mass than placebo, compared with just over a pound for whey, the most-studied supplement in the analysis.²⁴While this seems impressive, only five of its 78 trials tested collagen at all, none of them gave anyone whey as a comparison, and only two of them contributed to the fat-free mass ranking. In those two trials, the researchers gave their placebo group silicon dioxide, a powder with no Calories or protein. ^{25, 26} Most of the other trials on whey protein used a carbohydrate placebo, which has no protein but does supply Calories, and extra Calories lower the body’s protein needs.^{24, 27} So the collagen groups had an easier placebo group to beat, which artificially inflates its results when compared to whey protein.

Additionally, those two collagen trials come from one lab in Germany and likely share some of the same men. One paper reports a trial that ran in two phases with the results merged, and its first phase had 25 men. The other paper reports 25 men with the same average age, height, and weight as that first phase, so the ranking probably counted them twice.^{25, 26} Both trials measured fat-free mass with bioelectrical impedance, which estimates body composition from how an electrical current moves through the body and doesn’t reliably track changes in muscle. Muscle biopsies from the first phase showed fibers growing about the same amount with collagen as with placebo, which made the paper’s authors conclude that the extra fat-free mass was from connective tissue, not muscle.²⁵

A different pair of collagen trials that investigated strength data further support the idea that collagen protein is not uniquely beneficial for muscle. One found the same strength gains with collagen as with a carbohydrate placebo after 15 weeks of leg training. In that same study, there appears to be a hypertrophy advantage, as quadriceps volume on MRI grew more with collagen, about 15% versus 10%.28 However, the protein intake in the collagen group was higher (1.85 g/kg/d) compared to the placebo group (1.44 g/kg/d), and we know that intakes below around 1.6 g/kg/d can reduce muscle mass gain. Plus, the statistical differences weren’t different between the groups over time. The other measured leg strength two days after a single session of up to 200 bodyweight squats, which tests recovery from soreness more than strength.²⁹ All 4 collagen trials in the analysis used product supplied by the companies that make it.^{25, 26, 28, 29}

Taken together, collagen protein does contribute to the total daily protein intake, which is important for supporting muscle mass in the context of a mixed diet. Compared to other types of protein however, particularly whey, collagen protein does not appear to be superior for building muscle or strength.

Does collagen help tendons and ligaments?

Collagen protein does not appear to uniquely build or repair tendons, ligaments, or connective tissue in general. Training increases connective tissue protein synthesis, the rate at which the body rebuilds that tissue, and studies measuring that rate show collagen doesn’t raise it at rest or add to the increase from training.^{30, 16, 31, 32}

Does collagen make tendons stronger or stiffer?

Collagen protein does not appear to make tendons stronger or stiffer. In the largest tendon trial on collagen, 39 young men lifted for 15 weeks while taking 15 grams of collagen or a placebo daily, and there were no differences in their patellar tendons, as both groups got about 20% stiffer from the training alone.³³ Two much smaller trials in female soccer players did find stiffer tendons with collagen than with a placebo matched for Calories.^{34, 35} Many collagen supporters hold these studies up as proof of benefit, both trials had fewer than 10 players per group, the lead researcher in both knew who was getting collagen, the placebo contained no protein, tendon size didn’t differ between groups, and in the larger trial the stiffness difference only just reached statistical significance. When four trials with 111 people in total were pooled, collagen made no difference to tendon stiffness, and the larger tendon size it showed on scans was rated very low certainty by the authors of that analysis.²³

Clinically, some with hypermobility disorders like Ehlers-Danlos may be interested in a unique tendon-stiffening effect of supplemental collagen. To this author’s knowledge, no such study has been performed. Others concerned with tendinopathy may also be interested in tendon changes related to collagen supplementation, though the relationship between tendon structure and pain is more complicated. We discuss that in more detail here.

Does collagen help joint pain?

Supplemental collagen protein doesn’t seem to reliably decrease pain or improve function enough for most people to notice. The joint pain trials show small average improvements that mostly fall below the change people can notice. Most of them measure pain with a visual analog scale, a 100-millimeter line where 0 means no pain and 100 means the worst pain imaginable. In one of the larger studies, 180 active young adults with knee pain during exercise took 5 grams of collagen or a placebo daily for 12 weeks, and pain fell by about 22 points with collagen and about 16 points with placebo, a difference of about 6 points.37 The minimal clinically important difference (MCID) for this test is ~12-20 mm, the smallest change patients are likely to notice.^{37, 38, 39}

Overall, the data do not appear to support a reliable, clinically significant benefit of collagen supplementation on either mechanisms or outcomes relating to joint pain. 

Does collagen help knee osteoarthritis?

Collagen protein hasn’t been shown to reduce pain or improve function in individuals with knee osteoarthritis. One study compared collagen with glucosamine, another supplement of dubious efficacy, for knee osteoarthritis. It had no placebo group, which makes any improvement hard to attribute, and it found no clinically significant differences in pain or function between the groups.⁴⁰ A placebo-controlled pilot trial of type II collagen found no difference in pain, function, or other outcomes at 24 weeks. ⁴¹ A larger study of 250 patients with osteoarthritis found that collagen reduced knee pain by 4.7 points more than placebo, well under the threshold people notice.⁴²

The 2026 umbrella review pooled the osteoarthritis meta-analyses and found a small average reduction in self-reported pain and about a 10-point drop on the 100-point pain line across 7 trials, while the pain and physical function scores of a standard osteoarthritis questionnaire (WOMAC) didn’t change significantly._⁴³ Again, the 10-point average sits below the 12 to 20 points usually cited as noticeable, and well below the roughly 20 points estimated for knee osteoarthritis specifically.³⁹

Does collagen improve skin?

Collagen protein may produce a small improvement in skin hydration and elasticity readings in the lab, mostly in trials run or paid for by collagen companies. As of this publishing, no trial has demonstrated a difference people can see.

How do studies measure skin hydration and elasticity?

Hydration is usually measured with a corneometer, a probe that reads the electrical properties of the top ~10 to 20 micrometers of skin.⁴⁴ That layer is the stratum corneum, a layer of dead cells sitting well above the dermis, where collagen actually lives.⁴⁵ One problem here is that the corneometer’s readings shift with room humidity, temperature, and season, which is why one of the trials in these analyses adjusted for local weather after noting that earlier positive studies hadn’t.⁴⁶

Elasticity comes from suctioning a small patch of skin and recording how it snaps back, and earlier meta-analyses pooled several different indices from that test as if they measured the same property.⁴⁷ None of these readings tells you whether anyone can see a difference, and as far as we can find, nobody has established how large a change in either device reading a person would notice.

The bigger problem is that neither of these tests tells you whether anyone looked different. In the phase 3 trials for Daxxify (daxibotulinumtoxinA), a botulinum toxin approved for frown lines, success meant at least a two-grade improvement on a wrinkle scale, judged by both the investigator and the patient.⁴⁸ Validated photo scales graded by blinded raters already exist, and they’re what a skin trial should use if the claim is that people will look different.

What do the collagen skinstudies show?

Most of the available studies on collagen disagree, and much of the disagreement traces to data errors and industry funding.

Does Collagen Improve Skin Elasticity and Hydration?

Collagen may improve skin elasticity and hydration by a small amount on device readings, though the two largest analyses disagree about whether even that holds up. A 2023 meta-analysis of 26 trials and more than 1,700 people concluded that “hydrolyzed collagen supplementation can have positive effects on skin health, but further large-scale randomized control trials are necessary to confirm these findings.”⁴⁹ A 2025 meta-analysis of 23 trials found benefits for hydration, elasticity, and wrinkles overall, but not in trials without company funding or in the highest-quality trials, and concluded there’s no clinical evidence supporting collagen for skin aging.⁵⁰ 

The counterargument is that those independent and high-quality results still lean positive, so there may be small to moderate benefits. I think that’s a reasonable conclusion, though when you look at the data more closely, these effects get even smaller, if not outright disappearing. For example, a recent review went back to the trials behind the 2021 and 2023 meta-analyses and found data errors that make collagen look better than it is. The most common was entering a study’s standard error, which describes how precise an average is, where its standard deviation belonged. A standard deviation describes how spread out individual results are. This error makes the study look several times more precise than it was and inflates its effect. They also found misclassified instruments and a trial with no placebo group, and showed that the positive results came almost entirely from industry-sponsored trials.⁴⁷ 

The problem here is that nearly all collagen-skin studies are funded by industry. Five of the seven trials coded as independent in the 2025 meta-analysis had authors employed by collagen manufacturers, four companies in all, and got the independent label only because their funding statements didn’t name an outside sponsor.^{51, 52, 46, 53} The two trials with no industry ties we could find disagree. One, in 36 postmenopausal women, found better cheek elasticity after four weeks,⁵⁴ while the other followed 56 older women for six months and found no difference in the skin. ⁵⁵

How Big Is the Effect of Collagen On Skin?

Collagen’s potential effects on skin are small, if present at all. The 2025 analysis’s high-quality hydration estimate, the one that looks compatible with a moderate benefit, leans heavily on one small 2018 trial entered with an effect about six and a half times the size researchers usually call large. That trial reported standard errors, and treating them as standard deviations reproduces the published entry exactly, the same mistake the 2026 audit found in both earlier meta-analyses.⁵⁶, ^50, 47 Three of the trial’s six authors worked for the company that made the product and co-funded the study, yet the paper declares no conflicts of interest.⁵⁶

When we re-ran the published data with that entry corrected, the trial still favored collagen, but the high-quality hydration effect shrank to about a quarter of its published size, with a range running from slightly worse than placebo to a moderate benefit.^50, 56 Across all the trials, collagen still comes out modestly ahead on hydration and elasticity readings. The benefit shrinks as the trials get more rigorous, which could be from bias, though there are too few good studies to prove it.

Does Collagen Reduce Wrinkles?

Collagen does not appear to reduce wrinkles in any way that has been shown to be visible. The 2025 meta-analysis found fewer wrinkles with collagen overall, but not in trials without company funding or in the highest-quality trials, and no trial has shown a difference in wrinkles that people can see.⁵⁰ A trial that could show it would come from a group with no stake in the product, run at least six months, compare collagen against both a placebo and a taste-matched protein, and grade results with blinded photo ratings alongside patients’ own ratings. Until that trial exists, collagen may nudge device readings, but it’s not clear how those translate to what you see in the mirror.

Should you take collagen?

Based on the available evidence, supplementing with collagen does not appear to be uniquely beneficial. For most people, collagen isn’t worth taking for muscle, tendons, joints, or skin, because the outcome data don’t show it beating ordinary protein for muscle or producing changes people can notice elsewhere.

If building muscle is the goal, hit your daily protein target from whatever foods and supplements you like and will keep eating. As a muscle-building protein, collagen is a worse version of the protein you’re probably already eating, though it does count towards your daily intake anyway.

If tendon or joint pain is the goal, training does the work collagen gets credit for, and the larger trials haven’t found collagen adding to it. Our article on collagen and tendinopathy covers tendon pain in more detail.

If skin changes are the goal, there may be a small effect on device readings in company-run trials, but nobody has shown an effect you could see in the mirror, and nobody without industry ties has tested it properly.
This article accompanies theBarbell Medicine Podcast Episode 250.

Continue the discussion

Want to dig deeper? Jordan also discussed a collagen study on the BBM Forum, including a follow-up question about total protein intake and how to interpret the results. Read the collagen research discussion on the BBM Forum. Browse without an account, or create a free account to join the conversation.

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