Collagen vs protein — which supplement is better for muscle?

These get conflated in supplement marketing, but their evidence supports different uses. Collagen's most consistent findings are for skin hydration and elasticity and reduced osteoarthritis joint pain — multiple independent meta-analyses back this specifically. Its muscle and bone benefits are real but more modest, and only show up in trials where collagen is paired with resistance training in older adults, not on its own. Protein, meanwhile, has the much stronger and more extensively replicated evidence for what's often assumed to be collagen's job: building and preserving muscle mass and strength alongside resistance training, including specifically in older adults with sarcopenia. If your goal is muscle, protein has the far deeper evidence base; collagen's real, distinct strength is skin and joints, not muscle.