Collagen peptide powder is a popular protein supplement, heavily marketed toward women, but deserves some skepticism, especially when it comes to muscle growth.
Today’s article will look at the research and discuss:
- What are collagen peptides?
- Why collagen is inferior for muscle protein synthesis
- Where it might have a niche use (joint health and possibly skin)
- Why most marketing is misleading (and what the research says)
- Who (if anyone) should use it
- Why whey protein is superior
What Are Collagen Peptides?
Collagen peptides are small portions of collagen protein derived from animals or fish and sold as dietary protein supplements. It’s also called hydrolyzed collagen peptides to describe the breakdown of larger collagen molecules by hydrolysis into the smaller peptides (shorter chains of amino acids).
When you digest collagen peptides, stomach acid (HCl) and digestive enzymes (pepsin, pepsinogen, and pancreatic enzymes) break down the peptides into individual amino acids that are absorbed into the bloodstream and transported to the liver. You absorb the individual amino acids, not the collagen, which is an important point in our conversation.
Let’s also think about collagen in the body. There are at least 28 types of collagen protein, and collectively they make up about 25 to 30% of the body’s protein. Collagen provides structure and connection, and is found in the skin, joints, tendons, bones, and other connective tissues. (1)
Amino Acid Profile: Why Collagen Is a Low-Quality Protein
Whether you take marine collagen peptides or grass-fed collagen peptides, the amino acid profile is similar. Collagen has a high abundance of glycine (about 1/3), proline (about 10%), and hydroxyproline (about 13.5%). (1)
Unlike other animal protein sources, collagen is not considered a complete protein. Complete proteins contain all the essential amino acids, and collagen lacks tryptophan. Collagen is also very low in the amino acid leucine, which is required to stimulate muscle protein synthesis. (2)
For these reasons, collagen is considered a low-quality protein.
Collagen Vs. Whey Protein for Muscle Growth
Because of the low leucine content, collagen is a terrible protein supplement for building muscle. It’s probably the worst protein you can consume if your goal is muscle protein synthesis.
Let’s see what the gold standard human randomized controlled trials say.
In a randomized, double-blind trial, young participants received either whey protein (30 grams), collagen protein (30 grams), or a noncaloric placebo after resistance training. Over a 5-hour recovery period, researchers collected blood and muscle biopsy samples.
Those who took the whey protein had higher levels of leucine and essential amino acids in their blood, while those who took collagen had higher levels of glycine and proline, which makes sense. However, muscle protein synthesis rates were only higher in the whey protein group. There was no increase in connective tissue protein synthesis between groups. (3)
Another randomized controlled trial, this one in older women, suggested similar results. Women receiving whey protein showed greater results in short- and long-term increases in muscle protein synthesis than those receiving collagen, demonstrating that whey protein is superior for muscle growth. (4)
Does Collagen Help Joints or Skin?
Collagen isn’t helpful for muscle growth, but are they helpful for anything else? The most reported benefits of collagen peptides are for joint and skin health, but what does the research say?
The main problem with the claims for joint and skin health is that we don’t have a mechanism to explain how this works. The question is: how do we increase connective tissue synthesis?
Remember that collagen peptides are broken down into amino acids. When they are absorbed, these amino acids can be used anywhere in the body; they don’t automatically go towards collagen synthesis.
We know that ingesting enough leucine, from whey protein, drives muscle protein synthesis, but we don’t see the same thing with collagen and connective tissue synthesis.
In fact, we know from Luc Van Loon’s lab that a twice-daily 15-gram dose of collagen protein didn’t increase connective tissue synthesis more than a placebo in young adults engaging in intense resistance training. (5)
Although the mechanism is not understood, collagen peptides may benefit joint health, according to human research.
In a randomized, placebo-controlled trial, healthy, active participants received either 10 grams of collagen peptides or a placebo for 24 weeks. Those receiving the collagen had lower joint pain at rest, as assessed by a physician. They also self-reported lower joint pain at rest and with various activity. (6)
Another randomized controlled trial found similar results in a middle-aged population with joint discomfort. Participants received a collagen supplement or placebo. Those receiving collagen had reduced joint discomfort, including pain and stiffness, over 12 weeks. (7)
When it comes to collagen peptides and skin health, we must ask the same questions about mechanisms. There is no viable mechanism to explain why collagen peptide supplements would increase connective tissue synthesis or skin elasticity compared to other forms of protein.
A 2025 meta-analysis of 23 randomized controlled trials found that collagen supplements significantly improved skin hydration, elasticity, and the appearance of wrinkles. However, when researchers removed data from trials funded by pharmaceutical companies, they found that the same associations didn’t hold true. (8)
Low-quality studies, including those relying on subjective measures, suggested collagen improved skin elasticity, but the higher-quality studies suggested no effect. Based on this, it’s difficult to recommend collagen as a treatment for skin aging. (8)
What the Research Actually Shows
We’ve looked at some of the research, including the gold standard RCTs, and here’s where we stand:
- Muscle growth – collagen is the worst choice; choose whey protein instead
- Joint pain – possible benefits from collagen peptides
- Skin health – collagen probably does nothing
Who (If Anyone) Should Use Collagen?
Collagen protein is a good source of dietary glycine, proline, and hydroxyproline, so someone who needs more of these specific amino acids might benefit from collagen protein.
One example is during pregnancy, when glycine becomes conditionally essential, meaning that normally your body makes enough glycine, but with the increased demands of pregnancy, you must also get some from your diet. However, eating enough overall protein during pregnancy may also be sufficient. (9)
Overall, most people won’t benefit from collagen, but personalized nutrition comes into play for individual concerns.
Better Alternatives for Performance & Recovery
Collagen is the worst protein for building muscle. While just about any other protein source is better, the best option is whey protein. Whey protein is a complete protein and provides sufficient leucine and other branched-chain amino acids to stimulate muscle protein synthesis.
Outwork Nutrition’s Build Whey Protein Isolate provides 25 grams of high-quality, bioavailable, 100% whey protein per serving to promote muscle building and recovery. With a high leucine content, it activates muscle protein synthesis and supports your overall health and fitness goals.
Final Word
When it comes to collagen peptides benefits, the facts don’t support the health claims. Collagen companies have good marketing strategies, but their products aren’t any better than whey protein.
Instead of asking about the best collagen peptides to take, we should be asking if collagen is even the best protein source in the first place. If you want to build and maintain your lean body mass (and who doesn’t), whey is the superior option.
Collagen Peptides FAQs
Co collagen peptides actually work?
Collagen peptides are broken down into individual amino acids and are digested just like any other protein. There isn’t any strong mechanistic explanation they would uniquely improve skin, joints, or connective tissue compared to other protein sources.
Are collagen peptides good for building muscle?
No. Collagen is a low-quality protein for muscle growth because it is very low in essential amino acids, especially leucine, which is critical for stimulating muscle protein synthesis.
Do collagen peptides improve skin health?
Some studies suggest small improvements in skin appearance but rely on subjective measures (like self-reported surveys) rather than objective measures. The overall evidence is limited, low-quality, and may be confounded by conflicts of interest.
Are collagen peptides better than whey protein?
No. Whey protein is superior for muscle growth, performance, and recovery because it is a complete protein and contains significantly more leucine for stimulating muscle protein synthesis.
What are collagen peptides made of?
Collagen peptides are derived from animal connective tissue and are rich in the amino acids glycine, proline, and hydroxyproline, but lack sufficient essential amino acids to support muscle growth.
References
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Holwerda AM, van Loon LJC. The impact of collagen protein ingestion on musculoskeletal connective tissue remodeling: a narrative review. Nutr Rev. 2022 May 9;80(6):1497-1514. doi: 10.1093/nutrit/nuab083. PMID: 34605901; PMCID: PMC9086765.
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Paul C, Leser S, Oesser S. Significant Amounts of Functional Collagen Peptides Can Be Incorporated in the Diet While Maintaining Indispensable Amino Acid Balance. Nutrients. 2019 May 15;11(5):1079. doi: 10.3390/nu11051079. PMID: 31096622; PMCID: PMC6566836.
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Aussieker T, Hilkens L, Holwerda AM, Fuchs CJ, Houben LHP, Senden JM, VAN Dijk JW, Snijders T, VAN Loon LJC. Collagen Protein Ingestion during Recovery from Exercise Does Not Increase Muscle Connective Protein Synthesis Rates. Med Sci Sports Exerc. 2023 Oct 1;55(10):1792-1802. doi: 10.1249/MSS.0000000000003214. Epub 2023 May 19. PMID: 37202878; PMCID: PMC10487367.
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Oikawa SY, Kamal MJ, Webb EK, McGlory C, Baker SK, Phillips SM. Whey protein but not collagen peptides stimulate acute and longer-term muscle protein synthesis with and without resistance exercise in healthy older women: a randomized controlled trial. Am J Clin Nutr. 2020 Mar 1;111(3):708-718. doi: 10.1093/ajcn/nqz332. Erratum in: Am J Clin Nutr. 2020 Dec 10;112(6):1656. doi: 10.1093/ajcn/nqaa275. PMID: 31919527; PMCID: PMC7049534.
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Kirmse, M., Lottmann, T. M., Volk, N. R., DE Marées, M., Holwerda, A. M., VAN Loon, L. J. C., & Platen, P. (2024). Collagen Peptide Supplementation during Training Does Not Further Increase Connective Tissue Protein Synthesis Rates. Medicine and science in sports and exercise, 56(12), 2296–2304. https://doi.org/10.1249/MSS.0000000000003519
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Clark KL, Sebastianelli W, Flechsenhar KR, Aukermann DF, Meza F, Millard RL, Deitch JR, Sherbondy PS, Albert A. 24-Week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain. Curr Med Res Opin. 2008 May;24(5):1485-96. doi: 10.1185/030079908x291967. Epub 2008 Apr 15. PMID: 18416885.
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Mohammed A, He S. A Double-Blind, Randomized, Placebo-Controlled Trial to Evaluate the Efficacy of a Hydrolyzed Chicken Collagen Type II Supplement in Alleviating Joint Discomfort. Nutrients. 2021 Jul 18;13(7):2454. doi: 10.3390/nu13072454. PMID: 34371963; PMCID: PMC8308696.
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Myung SK, Park Y. Effects of Collagen Supplements on Skin Aging: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Am J Med. 2025 Sep;138(9):1264-1277. doi: 10.1016/j.amjmed.2025.04.034. Epub 2025 May 3. PMID: 40324552.
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Rasmussen BF, Ennis MA, Dyer RA, Lim K, Elango R. Glycine, a Dispensable Amino Acid, Is Conditionally Indispensable in Late Stages of Human Pregnancy. J Nutr. 2021 Feb 1;151(2):361-369. doi: 10.1093/jn/nxaa263. PMID: 32939556; PMCID: PMC7850138.
