Plant vs Animal Protein. Does It Actually Matter? | Educational Video | Biolayne

Norton builds this recommendation from the study's findings and his broader knowledge. He explains that when total protein is below ~1.6 g/kg, lower-quality plant proteins might underperform because the essential amino acid (especially leucine) dose is insufficient to fully stimulate muscle protein synthesis. However, once protein intake surpasses about 1.6 g/kg, even plant proteins provide enough leucine to max out the anabolic response, effectively 'capping out the anabolic system.' He concedes that in a perfect, very long-term RCT with resistance-trained people eating exactly 1.6 g/kg from predominantly plant vs. animal sources, there might be a tiny, almost undetectable difference, but in practice total protein intake is the overwhelming determinant. He also advises not to chronically under-fuel or diet on very low calories, as that hampers muscle building regardless of protein source. The message: prioritize hitting a high protein target, and the plant-animal debate largely vanishes.

Norton derives this protocol from the study’s lack of difference despite lower protein quality/quantity in vegetarians. He states that untrained people have 'such a robust response to resistance training' that the anabolic signal from the exercise alone can drive similar gains. Youth amplifies this because anabolic sensitivity is higher. He contrasts this with older or well-trained individuals, where the training stimulus is weaker, so nutrition becomes a bigger lever. The takeaway is not that beginners should eat poorly, but that they shouldn’t obsess over protein specifics if they are training hard. He notes that even at 1.0 g/kg in the vegetarian group, they built as much muscle as the 1.3 g/kg omnivore group, supporting a relaxed approach during the novice phase. This insight can reduce overwhelm and keep beginners focused on consistency.

Norton reviews a study where untrained women lifted twice a week for 16 weeks. The vegetarian group consumed about 1.0 g/kg protein, the omnivore group 1.3 g/kg. Despite the clear difference in protein quantity and likely quality (digestibility, amino acid score), DEXA scans and muscle thickness showed no differences. Norton explains that two factors likely erased any diet effect: the subjects were young and untrained. Young people are more anabolically sensitive, and untrained individuals experience a massive, generalized increase in muscle protein synthesis from resistance training—so large that dietary protein quality differences become invisible. He notes that 16 weeks is sufficient to detect diet-induced body comp changes in trained populations, but here the training stimulus drowned out the dietary variable. This, he says, is why people think studies contradict: a well-designed trial can produce a null result simply because the population’s inherent anabolic response is too strong for the dietary variable to register. His takeaway: for young, untrained beginners, nutrition quality matters far less than just training; with greater training age or older age, small differences from protein source may become apparent.