Collagen Protein: What It Is and Does It Work? 

Collagen is the most common structural protein 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, however types I, II, III, and IV are the most abundant in muscles, joints, and skin. ¹ 

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.² 

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. While this has not been shown in humans using anabolic steroids, tendon rupture in these individuals has been observed more frequently than others, and changes to the collagen in these tissues might be the cause.^{3, 4} 

Because of its presence in most of the body’s systems, it is an increasingly popular nutritional supplement, often billed as a sort of panacea for health and vitality. Companies and spokespeople confidently promise that it can alleviate sore joints and sagging skin. From 2018 to 2020, the global supplemental collagen market grew from an estimated 3.5 billion USD to approximately 8.4 billion USD, making it one of the fastest growing categories in nutritional supplements. ⁵ 

The question remains however, does supplementing with collagen protein actually work? 

What Is Supplemental Collagen? 

Supplemental collagen protein is usually derived from cows, pigs, or marine animals like jellyfish or sponges. ⁶ There are also other synthetic types of collagen that are used in clinical applications and as food additives. The majority of collagen protein supplements are “hydrolyzed”, which means the protein has been broken down by a chemical reaction involving water, heat, enzymes, or all of these reactants. 

While collagen supplements are generally safe if they are produced in compliance with Current Good Manufacturing Practices (CGMP) and tested by qualified third parties to ensure purity, some adverse effects have been noted. Researchers reported some immune reactions, although this was not common. ⁷ Far more worryingly, bovine spongiform encephalopathy, also known as mad cow disease, was identified in a case report and associated with gelatin and collagen consumption. ⁸ The risk of contracting this condition, whether from ingesting collagen or other from potential sources, is exceptionally rare. ⁹ 

How Much Protein Is in Collagen Powder? 

Protein content in supplemental collagen varies by manufacturer, with most being about 80% protein and the rest fat and carbohydrates. By comparison, whey protein isolate is typically greater than 90% protein by weight, whereas pea and soy proteins range between 77–81% and 61–91%, respectively. ¹⁰ 

However, protein by weight does not address how a given protein is used by the body because it omits the essential amino acid content of a protein source. Essential amino acids are a subset of protein building blocks that the body cannot synthesize through other means and must be consumed through food. The Protein Digestibility-Corrected Amino Acid Score (PDCAAS) takes the amino acid content of a protein source into account along with how readily humans can digest it. It is a widely accepted metric for protein quality.  

The Digestibility Score ranges from 0.0 (worst) to 1.0 (best) and is calculated by comparing a test protein to a reference protein, usually egg or milk. The ratio between the first essential amino acid found in the lowest amount in the test protein against the same amino acid in the reference provides the resulting number. The Digestibility Score for collagen protein is 0 because it lacks the essential amino acid tryptophan and is an incomplete protein. ¹¹  For comparison, the Digestibility Score of whey protein is 1.00. 

Branched Chain Amino Acids (BCAAs), which include leucine, isoleucine, and valine, are three of the essential amino acids that play important roles in building and preserving muscle in humans. The branched chain amino acid content of whey protein is nearly twice that of collagen. ¹²  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 likely make it less useful for supporting protein synthesis in the body. 

How Does Supplemental Collagen Protein Work? 

Supplemental collagen protein is said to work by delivering a relatively high amount of the amino acids glycine and proline, which are needed for the body to make collagen. Not surprisingly, supplemental collagen is rich in these amino acids, whereas whey, casein, egg, and beef protein are much lower. Glycine and proline are not essential amino acids and the body can synthesize them even when they are not present in food. 

Theoretically, if someone were to consume high amounts of glycine and proline by taking supplemental collagen protein, that would prompt the body to create more collagen and incorporate that collagen into the tissues where it is most needed. Presumably, this would help improve conditions associated with loss of or damage to collagen, such as tendon or ligament injuries, aging skin, and so on. While seemingly logical, the chances this would occur are low and rely more upon wishful thinking than an observed mechanism or chain of events in the body.  

Importantly, collagen protein and the amino acids glycine and proline are not just found in supplements but also found in many foods. Many types of animal protein, egg whites, and spirulina (a type of algae often used as a supplement), contain both collagen protein and the amino acids glycine and proline.  It is also rare for people to be deficient in glycine or proline due to its absence in the diet, and this is not likely a limiting factor for collagen synthesis.   

In the following sections, the science underlying how supplemental collagen protein affects muscles, connective tissue, skin, and clinical outcomes like pain will be reviewed. 

What Does Collagen Protein Do for Muscles? 

Collagen is not a particularly good protein source for building muscle because it lacks the essential amino acid tryptophan. Human bodies cannot synthesize tryptophan, so it must be obtained from the diet. Also, its digestibility is much lower than other protein sources such as meat, dairy products, eggs, and whey protein. This is supported by research showing that 30 grams of collagen protein did not stimulate muscle protein synthesis, whereas 30 grams of whey protein did. ¹³ 

A recent meta-analysis of 19 randomized controlled trials showed that supplemental collagen protein added to an individual’s habitual diet may increase strength and size compared to not consuming additional protein. However, collagen protein is not as effective as whey protein, even when the critical branched chain amino acid leucine is added to the collagen protein supplement. ¹⁴ 

Overall, it does not appear that collagen protein is a suitable replacement for whey or other supplemental proteins that are rich in essential amino acids when targeting muscle mass and strength improvements. 

What Does Collagen Protein Do for Ligaments and Tendons (Connective Tissue)? 

The evidence is not promising when it comes to supplemental collagen protein providing benefits to connective tissues like tendons and ligaments. Most studies suggest that consuming collagen protein does not increase connective tissue protein synthesis, although lifting weights appears to effectively stimulate this. ¹² A recent meta-analysis also showed no difference in tendon mechanical properties with collagen protein supplementation compared to placebo. ¹⁴ 

Is Collagen Protein Good for Joint Pain? 

Supplemental collagen protein does not seem to decrease tendon pain or improve function. For example, a recent study where young men took 15 g of collagen peptides per day or a placebo while lifting three times per week, showed no difference between groups in the size of their patellar tendon or function after 15 weeks with respect to musculoskeletal pain. ¹⁵ 

Another study compared collagen supplementation to glucosamine (another supplement of dubious efficacy) for treating knee osteoarthritis. Unfortunately, there was no control group receiving a placebo, making attribution of any improvement difficult. There were no clinically significant differences in pain or function between the groups. ¹⁶ 

In a placebo-controlled collagen supplementation trial, there was no difference in pain, function, or other outcomes in those with knee osteoarthritis at 24 weeks. ¹⁷ Finally, a larger study of 250 patients with osteoarthritis showed no clinically significant difference in knee pain in those with osteoarthritis. ¹⁸ 

Numerous studies make claims regarding statistically significant differences in pain scores. Pain can be quantified by using the Visual Analog Scale, which is a line, often 100 mm long, with the 0 mm end indicating the absence of pain and 100 mm end indicating the worst imaginable pain someone could experience. In the case of the Benito-Ruiz et al. 2009 paper, the authors found a difference between placebo and collagen of 4.7 mm between groups, with collagen protein reducing pain ratings more on a 100 mm scale. However, the minimal clinically important difference (MCID) for this test is 13.7 mm, making the reported difference unlikely to be meaningful. 

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. 

What Does Collagen Protein Do for Skin? 

Another common use case for supplemental collagen is “skin health”, which is a poorly defined concept. Definitions aside, normal skin aging is often characterized by dehydration, a loss of elasticity, and the presence of wrinkles. It is thought that as we age, specific enzymes needed to produce collagen in the skin decline, thereby leading to reduced synthesis and the increasing prevalence of these changes. 

A recent meta-analysis that involved 26 randomized control trials and over 1700 patients looked at how collagen supplementation affected skin hydration and elasticity levels. The authors reported that “Overall, the findings suggest that hydrolyzed collagen supplementation can have positive effects on skin health, but further large-scale randomized control trials are necessary to confirm these findings.” ¹⁹  Unfortunately, some methodical flaws in the meta-analysis, coupled with the heterogeneity in the quality and methods of the underlying studies, make such optimism difficult to justify. 

The claim that ingesting supplemental collagen improves skin hydration and elasticity appears to be weakly supported, at best.  

The Bottom Line: Should You Take Collagen? 

Based on the available evidence, supplementing with collagen does not appear to be beneficial. Recommending supplemental collagen protein relies upon a seemingly implausible mechanism — specific amino acids consumed in the diet will intelligently travel to specific sites in the body rather than undergo traditional protein metabolism. It seems unlikely that collagen protein is made up of “smart” amino acids that can be preferentially directed towards the desired tissues, even if primed to do so by lifting weights prior to ingestion. 

Instead, it is more likely that increasing dietary protein may improve the outcomes discussed here, with the source of that protein being relatively unimportant. Ideally, studies on supplemental collagen protein would compare a specific dose of collagen to an energy-matched, non-protein placebo, as well as to an energy-matched whey protein group or similar. As of this writing, there are no supportive studies showing that supplementing with collagen protein specifically has a unique benefit as compared to whey or other protein supplement. 

With respect to muscle mass, most data shows that supplemental collagen protein does not increase muscle protein synthesis rates or muscle mass as much as other forms of protein, particularly whey. Collagen protein is also typically more expensive than other supplemental protein and protein from whole foods. 

When it comes to the ligaments, tendons, and other connective tissue found in joints, supplementing with collagen is generally not effective. Mechanistically, supplemental collagen does not appear to reliably increase connective tissue protein synthesis, making it unlikely that tendons, ligaments, or other connective tissue undergo any significant changes. Available data on joint pain corroborates this claim, with collagen protein failing to outperform placebo in a meaningful way. 

The results of supplemental collagen on skin-related outcomes are less clear due to methodological concerns, but existing data are not promising. Overall, collagen protein is more expensive and generally less effective when compared to other supplemental proteins and protein from whole foods. Based on existing data, there is no need to take supplemental collagen protein nor is it likely provide positive results for skin. 

This article accompanies the Barbell Medicine Podcast Episode 250.

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