Hormonal

Higher-quality protein sources (e.g., whey, milk) produce a significantly greater acute muscle protein synthesis (MPS) response than lower-quality sources (e.g., soy, wheat, casein) when matched for dose, both at rest and following resistance exercise.

If you are trying to maximize muscle growth, prioritize high-quality protein sources like whey, milk, eggs, or meat over lower-quality plant proteins (like wheat or soy) when possible. This is especially relevant for older adults who may experience 'anabolic resistance.' However, this is a small effect; hitting your total daily protein target is still the most important factor.