For those research geeks among you, here are the references:
Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am J Clin Nutr. 2009.
A moderate serving of high-quality protein maximally stimulates skeletal muscle protein synthesis in young and elderly subjects. Journal of the American Dietetic Association, 2009.
So, what did these landmark studies show?
Well, the first study showed that when college-aged weight-trainers drink 0g, 5g, 10g, 20g, or 40g of protein after a weight training session, muscle protein synthesis is stimulated maximally at the 20g dose. Interestingly, there were no further increases in muscle protein synthesis at the 40g dose.
Similarly, in the second study, when young and elderly volunteers were given 30 or 90g of dietary protein in a single meal, the 30g dose maximally stimulated muscle protein synthesis. Again, there were no further increases in muscle protein synthesis at the 90g dose.
https://www.precisionnutrition.com/protein-limit