Collagen for bulking: is there any point

During a bulking phase, athletes focus on calories and protein, while collagen is usually seen as a “women’s” supplement for the skin. Yet on the label it looks like almost pure protein, and some view it as a cheaper protein substitute. The editorial team looked into whether collagen makes sense on a bulk, what the research says about hypertrophy, and where it can actually be useful.

Protein on a bulk: what matters for hypertrophy

The position of the International Society of Sports Nutrition (Jäger et al., 2017) states that for most people who do strength training, optimal protein intake is roughly 1.4–2.0 g per kilogram of body weight per day. Splitting it into several servings of 20–40 g helps sustain muscle protein synthesis throughout the day.

Protein quality matters no less than quantity. To trigger the anabolic response of muscles, a sufficient amount of essential amino acids is needed, especially leucine. ISSN guidelines cite a benchmark of about 700–3000 mg of leucine per meal, depending on body weight and protein source.

On a bulk, a caloric surplus partly “softens” the importance of protein quality: the body gets plenty of energy and varied food. However, this does not mean that any protein is equally good for muscles. Differences between sources persist.

That is exactly why the question arises: can collagen, which on the label often contains 90% protein, be a full participant in the protein allowance on a bulk?

The amino acid profile of collagen

Collagen consists mainly of glycine, proline, hydroxyproline and alanine. It has far fewer essential amino acids than whey, egg or meat protein. Collagen has virtually no tryptophan, so by protein quality classification (PDCAAS or DIAAS) it is considered incomplete.

Collagen contains several times less leucine than whey protein. To get as much leucine from collagen as from a single serving of whey, you would have to eat an impractically large amount of it, and other essential amino acids would still be lacking.

Collagen, on the other hand, has an advantage that “muscle” proteins lack: a high content of glycine and proline — the main building blocks of connective tissue. For tendons, ligaments and bones this profile can be useful.

It follows that collagen and whey do not compete but perform different functions. The only question is what exactly is the priority in a given period.

What hypertrophy studies show

Advertising most often cites the study by Zdzieblik and colleagues (2015), in which elderly men with sarcopenia who took 15 g of collagen peptides together with strength training gained more lean mass than those who took placebo. A similar design was used by Kirmse and colleagues (2019) on young trained men, who also reported a small advantage of collagen over placebo.

An important detail: in both studies the control group received no additional protein at all. That is, they compared “collagen” with “nothing.” Any additional protein under such conditions can provide an advantage, so these results do not prove any special muscle-building properties of collagen.

When collagen was compared directly with a complete protein, the results favored the latter. Oikawa and colleagues (2020) showed that whey protein stimulated muscle protein synthesis more strongly than collagen peptides — both in an acute experiment and over several days.

So as a protein source for hypertrophy, collagen is inferior to classic proteins. It does not “harm” a bulk, but it is not an effective substitute for whey or casein either.

Tendons don’t keep up with muscles

On a bulk, working weights often increase: the athlete gets stronger and loads the joints and tendons more than before. Muscles adapt fairly quickly, while tendons renew more slowly. This imbalance is considered one of the factors behind tendinopathies in strength sports.

This is exactly where collagen may find its place. A study by Shaw and colleagues (2017) showed that taking gelatin with vitamin C before exercise increases a marker of collagen synthesis in the blood. A review by Holwerda and van Loon (2022) concludes that collagen proteins may support connective tissue remodeling, although clinical evidence for injury prevention is still insufficient.

It is also interesting that training studies with collagen sometimes record changes in tendons and the extracellular matrix of muscles, not only in the contractile fibers. This is an area where collagen’s potential is greater than in “classic” hypertrophy.

For an athlete on a bulk who has problem tendons or is recovering from an injury, collagen may be a reasonable addition. For someone who simply wants “more protein,” it is better to choose a complete protein.

A practical model for the bulking period

Collagen is a dietary supplement, so practical guidelines can be formulated. The editorial team suggests the following sequence of decisions:

1. Calculate your daily protein requirement (1.6–2.2 g/kg) and cover it with meat, fish, eggs, dairy products or protein powder.
2. Do not count collagen toward this allowance if you want to control protein quality precisely.
3. If there is a need to support the tendons — add 10–15 g of collagen or gelatin with 50–100 mg of vitamin C 30–60 minutes before training.
4. Assess the subjective condition of your joints after 2–3 months, not after a few workouts.

The economic aspect matters too: if your budget is limited, on a bulk it is better to invest money in quality complete protein and food. Collagen is the second line, not the first.

Collagen’s side effects are minimal, but on a bulk additional protein increases the overall load on the digestive system. If bloating or heaviness appears, it is worth redistributing the servings.

Editorial conclusions

As a protein for building muscle mass, collagen has limited value: it is low in leucine and has no tryptophan, and direct comparisons with whey do not favor it.

Studies in which collagen “helped gain mass” compared it with a protein-free placebo, so they do not prove any special properties of the supplement.

Collagen’s real niche on a bulk is supporting the tendons and ligaments, which do not keep up in adapting to increasing working weights. Here it can be a relevant addition to a complete diet.

We also recommend reading our articles “Collagen when cutting: does it help,” “The history of collagen: how the supplement became popular” and “How to choose quality collagen: what to look for on the label.”

References

1. Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20.
2. Zdzieblik D, Oesser S, Baumstark MW, et al. Collagen peptide supplementation in combination with resistance training improves body composition and increases muscle strength in elderly sarcopenic men: a randomised controlled trial. Br J Nutr. 2015;114(8):1237–1245.
3. Kirmse M, Oertzen-Hagemann V, de Marées M, et al. Prolonged collagen peptide supplementation and resistance exercise training affects body composition in recreationally active men. Nutrients. 2019;11(5):1154.
4. Oikawa SY, Kamal MJ, Webb EK, et al. 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;111(3):708–718.
5. Shaw G, Lee-Barthel A, Ross ML, et al. Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. Am J Clin Nutr. 2017;105(1):136–143.
6. Holwerda AM, van Loon LJC. The impact of collagen protein ingestion on musculoskeletal connective tissue remodeling: a narrative review. Nutr Rev. 2022;80(6):1497–1514.