The leucine threshold and why it anchors the comparison
Muscle protein synthesis appears to respond most strongly once a meal delivers roughly 2.5 to 3 grams of leucine, an amount sometimes called the leucine threshold. Whey reaches about 3 grams of leucine in a typical 30 gram protein dose, which is why it is used as the high reference point.
Plotting leucine per 30 grams of protein, rather than per gram of food, isolates protein quality from how much you have to eat to get there.
Why many plant proteins fall short per equal dose
Most plant proteins contain less leucine per gram of protein than animal sources, so a 30 gram dose of many plant proteins lands below the 2.5 gram leucine mark. That can mean a smaller acute muscle-building signal from a single matched dose.
The practical workaround is straightforward: eat a somewhat larger plant-protein serving, combine complementary sources, or distribute protein across more meals to clear the threshold over the day. A lower per-dose leucine figure is a quality difference, not a barrier to building muscle on a plant-based diet. General educational information, not personalized dietary advice.