A common thought is that there is a maximum amount of protein that can be metabolized in one sitting. It has been typically stated that the anabolic window reaches a cap at 30 g of protein per meal.
There is no specific amount of protein an individual should consume but the specific number is going to be dependant on an individuals specific goals and body composition. Currently the RDA suggests that a healthy individual should be consuming .8 g/ kg of BW per day and 1.4- 1.6 g/kg of BW for a more active individual
Additionally, the training stimulus must be adequate to result in strength improvement, regardless of protein timing, total protein intake, or nutritional status. Protein supplementation by individuals participating in ineffective resistance training programs will be less impactful.
Although, there are multiple factors that contribute to quantifying the maximum amount of protein; dietary programming needs to be individualized to each person based on their goals, their level of activity, their dietary restrictions, if the protein source is fast vs slow absorbing. From our findings, a study done by Morton et al. concluded that .4g/ kg/ meal would optimally stimulate muscle protein synthesis- but this conclusion is based on the speed of digestion.
This information can be applied to what we currently know about protein and how to maximize anabolic adaptations. While research shows that consumption of higher protein doses (> 20 g) results in greater AA oxidation, there is evidence that excess protein will not go to waste; rather potentially used for tissue-building purposes.
Further research is nevertheless needed to quantify a specific upper threshold for per-meal protein intake.
Schoenfeld, B. J., & Aragon, A. A. (2018). How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition, 15(1), 1-6.