Plant-based proteins are thought to be inferior to animal-based proteins because (i) they generally contain lower amounts of essential amino acids overall; (ii) they often contain an inadequate amount of one or more specific EAAs (typically lysine, methionine, and/or leucine), and a sufficient amount of all EAA are needed to sustain muscle protein synthesis (MPS); and (iii) they are generally less digestible, meaning that a lower amount of EAA are available for muscle tissue after consuming plant-based proteins.[1]
There are ways around these issues, however. For starters, while whole food sources of plant-based proteins are generally less digestible than whole food sources of animal-based protein sources, this does not appear to be the case for protein powders.[2]
Second, it’s possible to compensate for lower amounts of EAA simply by consuming a larger amount of plant-based protein. Research indicates that when a dose of 30 grams of a plant-based protein powder is consumed — regardless of whether it’s derived from wheat, potato, corn, pea, or a combination of sources — a rise in MPS is achieved that is comparable to that of milk protein.[3][4][5][6] Similar results were also reported in a study that compared chicken breast to a lysine-enriched meat alternative composed of wheat and chickpea protein.[7]
Moreover, most of us don’t consume a single isolated protein source. From a whole diet perspective, protein intake is typically derived from a variety of foods.
Finally, it’s important to consider the elephant in the room here: acute increases in MPS aren’t necessarily predictive of longer term muscle gains,[8] and the accumulation of muscle mass occurs over a weeks-to-months timescale, rather than minutes-to-hours. So, it’s prudent to question the model used to assess differences in the “muscle-building ability” of plant- and animal-based proteins. This brings us to the central question of importance: can vegan and omnivorous diets similarly support resistance exercise-induced adaptations?
The answer seems to be yes. In two separate studies in young adults that included a resistance exercise intervention and randomized the participants to consume a high-protein diet (≥1.6 grams per kilogram of body weight per day), either mostly from animal-based proteins or exclusively from plant-based proteins, both found comparable increases in muscle size and strength between groups after a few months.[9][10]
In sum, the collective evidence suggests that as long as total daily protein intake is sufficiently high and a variety of plant-based proteins are consumed, vegan and omnivorous diets are equally effective for increasing muscle size and strength.