While it is true that collagen is low in leucine and doesn’t strongly stimulate muscle protein synthesis (MPS) via mTOR, mTOR isn’t the only anabolic pathway that matters. Other signaling networks—such as PI3K/Akt and MAPK—play major roles in connective-tissue remodeling, tendon support, and muscle repair.
A 2022 randomized controlled trial in Frontiers in Physiology reported that 15 g of collagen peptides consumed after high-load resistance exercise significantly increased activation of both PI3K/Akt and MAPK versus placebo [1]. That’s notable given many whey studies use ~30 g doses. These pathways are linked not only to muscle growth but also to strengthening the extracellular matrix—the “scaffolding” that transfers force from muscle to bone.
Beyond signaling, collagen is the most abundant protein in the body, accounting for ~30% of total protein [2]. The body contains at least 16 types of collagen distributed across skin, tendons, bone, cartilage, and other connective tissues.
Collagen isn’t ideal as your only protein source, but it’s far from useless. It targets complementary adaptation pathways. When paired with higher-leucine proteins throughout the day, collagen can support joint health, connective-tissue integrity, and overall muscle health.
References:
[1] Centner et al., 2022. Frontiers in Physiology. https://doi.org/10.3389/fphys.2022.838004
[2] Deshmukh et al., 2016. Journal of Oral and Maxillofacial Pathology. https://doi.org/10.4103/0973-029X.185932