About this Resource
Protein intakes are one of the primary nutritional considerations for building and maintaining lean body mass (i.e., muscle). The recommended dietary allowance (RDA) for protein is around 0.8 grams of protein per kilogram (kg) of body weight. However, for active individuals, particularly those heavily engaged in resistance training, recommended protein intakes are thought to be much higher to compensate for the damage caused to muscle fibres.
Grounded in the Research
“Current data suggest that dietary protein intake necessary to support metabolic adaptation, repair, remodeling, and for protein turnover generally ranges from 1.2 to 2.0 g/kg/d. Higher intakes may be indicated for short periods during intensified training or when reducing energy intake.”
Excerpt from: Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). Nutrition and athletic performance. Med. Sci. Sports Exerc, 48(3), 543-568.
How Muscle is Built
Skeletal muscle mass is regulated by dynamic and continuous fluctuations in muscle protein synthesis (MPS) and muscle protein breakdown (MPB). [7] Muscle growth occurs when MPS exceeds MPB, resulting in a net positive protein balance. [8]
Engaging in resistance training is the most potent MPS stimulus, followed by sufficient intake of amino acids — the constituent building blocks of dietary proteins. [5] Therefore, protein intakes are a key consideration for those wanting to maximise muscle growth.
How Much Protein Do You Need Each Day?
The recommended dietary allowance (RDA) for protein is 0.8 grams of protein per kilogram (kg) of body weight and this is thought to be sufficient to meet requirements for 97.5% of adults. [3]
On the other hand, the RDA is often misinterpreted as an optimal protein intake and some researchers have argued that it might more helpfully be called a ‘recommended minimum intake’. [8, 10]
How Much Protein is Optimal for Muscle Growth?
It is well established that individuals heavily engaged in physical activity have greater protein needs than sedentary individuals. [9] Therefore, the RDA may not be an appropriate intake range for this population.
In line with this, many professional organisations involved in the development of sports nutrition guidelines advocate a protein intake range which is around twice the RDA for active individuals. [8]
The joint position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine states that a range of 1.2–2.0 grams of protein per kilogram of body weight, per day (g/kg/d) is recommended. [11] The International Society for Sports Nutrition also recommends protein intakes between 1.4–2.0 g/kg/d for physically active individuals. [9]
In 2018, a comprehensive meta-analysis (a study of studies) conducted by Robert Morton and colleagues highlighted that a protein intake beyond 1.6 g/kg/d led to no further increases in fat-free mass (i.e., muscle) when combined with resistance training. [5]
Expressed in a another way, a protein intake of 1.6g/kg/d, on average, appeared to be the optimal intake for those wanting to maximise their muscle growth. [5] This figure of 1.6 grams of protein per kilogram of body weight per day has been supported by subsequent meta-analyses. [12] Therefore, this appears to be a reasonable target intake for individuals wanting to maximise their muscle growth.
On the other hand, the researchers Brad Schoenfeld and Alan Aragon (who were co-authors on the meta-analysis conducted by Morton and colleagues) cautioned that: “1.6 g/kg/day should not be viewed as an ironclad or universal limit beyond which protein intake will be either wasted or used for physiological demands aside from muscle growth” [6].
They highlight that the upper confidence interval in the research was 2.2 g/kg/day and therefore: “reinforces the practical need to individualize dietary programming, and remain open to exceeding estimated averages.”[6]
References
[1] Atherton, P. J., & Smith, K. (2012). Muscle protein synthesis in response to nutrition and exercise. The Journal of Physiology, 590(5), 1049-1057. https://doi.org/10.1113/jphysiol.2011.225003
[2] Pearson, A. G., Hind, K., & Macnaughton, L. S. (2023). The impact of dietary protein supplementation on recovery from resistance exercise-induced muscle damage: A systematic review with meta-analysis. European Journal of Clinical Nutrition, 77(8), 767-783. https://doi.org/10.1038/s41430-022-01250-y
[3] Rand, W. M., Pellett, P. L., & Young, V. R. (2003). Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults. The American Journal of Clinical Nutrition, 77(1), 109-127. https://doi.org/10.1093/ajcn/77.1.109
[4] Hudson, J. L., Wang, Y., Bergia III, R. E., & Campbell, W. W. (2020). Protein intake greater than the RDA differentially influences whole-body lean mass responses to purposeful catabolic and anabolic stressors: a systematic review and meta-analysis. Advances in Nutrition, 11(3), 548-558. https://doi.org/10.1093/advances/nmz106
[5] Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., … & Phillips, S. M. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6), 376-384. https://doi.org/10.1136/bjsports-2017-097608
[6] 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), 10. https://doi.org/10.1186/s12970-018-0215-1
[7] Damas, F., Libardi, C. A., & Ugrinowitsch, C. (2018). The development of skeletal muscle hypertrophy through resistance training: the role of muscle damage and muscle protein synthesis. European Journal of Applied Physiology, 118(3), 485-500. https://doi.org/10.1007/s00421-017-3792-9
[8] Carbone, J. W., & Pasiakos, S. M. (2019). Dietary protein and muscle mass: translating science to application and health benefit. Nutrients, 11(5), 1136. https://doi.org/10.3390/nu11051136
[9] Jäger, R., Kerksick, C. M., Campbell, B. I., Cribb, P. J., Wells, S. D., Skwiat, T. M., … & Antonio, J. (2017). International society of sports nutrition position stand: protein and exercise. Journal of the International Society of Sports Nutrition, 14, 1-25. https://doi.org/10.1186/s12970-017-0177-8
[10] Wolfe, R. R., Cifelli, A. M., Kostas, G., & Kim, I. Y. (2017). Optimizing protein intake in adults: interpretation and application of the recommended dietary allowance compared with the acceptable macronutrient distribution range. Advances in Nutrition, 8(2), 266-275. https://doi.org/10.3945/an.116.013821
[11] Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: nutrition and athletic performance. Journal of the Academy of Nutrition and Dietetics, 116(3), 501-528. https://doi.org/10.1016/j.jand.2015.12.006
[12] Tagawa, R., Watanabe, D., Ito, K., Otsuyama, T., Nakayama, K., Sanbongi, C., & Miyachi, M. (2022). Synergistic Effect of Increased Total Protein Intake and Strength Training on Muscle Strength: A Dose-Response Meta-analysis of Randomized Controlled Trials. Sports Medicine-Open, 8(1), 110. https://doi.org/10.1186/s40798-022-00508-w
[13] Norton, L. E., & Layman, D. K. (2006). Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. The Journal of Nutrition, 136(2), 533S-537S. https://doi.org/10.1093/jn/136.2.533s
[14] Zaromskyte, G., Prokopidis, K., Ioannidis, T., Tipton, K. D., & Witard, O. C. (2021). Evaluating the leucine trigger hypothesis to explain the post-prandial regulation of muscle protein synthesis in young and older adults: a systematic review. Frontiers in Nutrition, 8, 685165. https://doi.org/10.3389/fnut.2021.685165