Animal-based proteins are generally higher quality than plant-based proteins because they contain adequate amounts of all the essential amino acids (EAA) and are better digested and absorbed.[1] Consequently, studies typically report a greater increase in muscle protein synthesis (MPS) following the ingestion of animal-based proteins.[2]
To overcome the lesser anabolic properties of plant-based proteins, a greater amount of protein can be consumed.[3][4] In a 3-day study in older adults (average age of 66), daily MPS rates did not differ between a high-protein (1.8 grams of protein per kilogram of body mass per day) vegan diet that provided 57% of protein as mycoprotein and a high-protein omnivorous diet.[5]
An alternative (or even additional) strategy is to combine different plant-based proteins to provide a balanced EAA profile,[6] as plant-based proteins typically contain an inadequate amount of one or more EAA.
While studies looking at acute changes in MPS are informative, they do not directly reflect longer-term changes in muscle mass and strength, which is what we’re really concerned with.
Evidence suggests plant- and animal-based protein supplements have a similar effect on changes in muscle mass and strength in older adults (≥ 50 years).[7] However, consuming an omnivorous diet and obtaining 25–50 grams of protein per day from a plant-based protein supplement is very different from consuming a vegan diet.
A 12-week study in young men demonstrated that a high-protein (1.6 grams per kilogram of body mass per day) vegan diet promoted comparable increases in leg lean mass and muscle strength as a high-protein omnivorous diet.[8] Unfortunately, a similar study has yet to be conducted in older adults, so the consequences of consuming a vegan diet on muscle mass and strength in this population remains unclear.
As it stands, the source of protein doesn’t seem to matter all that much, as long as enough total protein is consumed each day.