Controversy abounds about the optimal amount of single-meal protein for lean tissue-building. It has been proposed that muscle protein synthesis is maximized in young adults with an intake of 20g–25g; anything above this amount is believed to be oxidized for energy or transaminated to form urea and other organic acids. However, these findings are specific to the provision of fast-digesting proteins without the addition of other macronutrients. Consumption of slower-acting protein sources, particularly when consumed in combination with other macronutrients, would delay absorption and thus conceivably enhance the utilization of the constituent amino acids.
Research indicates that total daily protein intake for the goal of maximizing resistance training-induced gains in muscle mass and strength is approximately 1.6g/kg/day, at least in non-dieting conditions. However, 1.6g/kg/day should not be viewed as a universal limit. A recent meta-analysis on protein supplementation involving resistance trainees reported an upper 95% confidence interval (CI) of 2.2 g/kg/day. Bandegan et al. also showed an upper CI of 2.2 g/kg/day in a cohort of young male bodybuilders, although the method of assessment (indicator amino acid oxidation technique) used in this study has not received universal acceptance for determining optimal protein requirements.
This reinforces the practical need to individualize dietary programming and remain open to exceeding estimated averages. Using the upper CI daily intake of 2.2 g/kg/day over the same four meals would necessitate a maximum of 0.55 g/kg/meal. This tactic would apply what is currently known to maximize acute anabolic responses as well as chronic anabolic adaptations. While research shows that consumption of higher protein doses (> 20 g) results in greater AA oxidation, evidence indicates that this is not the fate for all the additional ingested AAs as some are utilized for tissue-building purposes.
Journal of the International Society of Sports Nutrition 2018 15:10
