Updated: Aug 10, 2021
Protein is an essential macronutrient to maintain normal physiological and structural functions in the body. There has been a lot of debate in terms of the type, amount, and timing of protein intake in trained individuals in both endurance and resistance sports. The purpose of this article is to review established guidelines for protein intake and timing based on the available literature and provide clear recommendations to be applied pre, during and after training as well as to the daily athlete’s nutrition regimen.
There are 20 amino acids including 9 essential amino acids (EAA’s) and 11 non-essential amino acids (NEAA’s). Essential Amino Acids cannot be produced by the body and must be obtained from external sources. Protein quality is determined by different m
ethods that are not going to be discussed in this article but, ultimately, protein quality is evaluated in terms of stimulation of Muscle Protein Synthesis (MPS) and promotion of muscle hypertrophy (Jager et.al. 2017).
Research has shown that protein sources containing the highest percentage of EAAs has resulted in higher MPS and muscle hypertrophy than other sources of protein sources such as vegetarian proteins. Within EAAs, the Branched Chain Amino Acids (BCAA’s) leucine, isoleucine, and valine are known to be fundamental for protein synthesis, blood glucose and insulin metabolism and neural function. After consumption, they rapidly increased amino acid blood levels exposing muscle to high available concentrations for skeletal muscle protein synthesis (Jager et. al., 2017).
Leucine itself plays an essential role in stimulation of the mammalian target rapamaycin (mTOR) signaling pathway and it has been indicated as the main stimulator of protein synthesis, therefore consumption of food sources and protein supplements with high leucine content is fundamental for muscle recovery and development. Approximately 3-4g of leucine per serving is needed to promote maximal protein synthesis stimulation (Stark, et.al., 2012).
How Much Should I Eat?
Recommendations for adequate protein intake vary in terms of individual characteristics (age, gender, and body composition), total energy intake and training status, type and volume of exercise, and the pre existence of stress factors and illnesses or injuries (Jager et. al., 2017).
It has been proposed that a minimum of 1.4-2.0g/kg of protein might be effective to maintain fat free mass while restricting caloric intake while working on making body composition changes. For athletes, it has been recommended at least 0.25 g of high biological value (HBV) protein per kg of body weight per meal is consumed to promote protein synthesis and muscle recovery or an overall intake of 20-40g per meal (40g for whole body workouts and 20g for split body workouts). In addition, it is recommended to consume protein evenly distributed during the day, every 3-4 hours to prevent negative nitrogen balance and muscle breakdown (Jager, et.al., 2017).
It is well known that, in the absence of feeding or in fasting state, muscle protein or nitrogen balance remains negative. As previously stated, a protein intake of 20-40g per meal (including 10-12g of EEA’s and 1-3g of leucine) stimulates MPS and promotes a positive nitrogen balance and muscle hypertrophy in combination with resistance exercise. Additionally, consumption of carbohydrates and protein sources during both endurance and resistance training promotes muscle hypertrophy, decreases muscle breakdown and perceived fatigue during long bouts of cycling and running (Jager et. al., 2017).
Finally, research has shown that consumption of protein in carbohydrate restricted (below 1.2/kg) and weight loss nutrition regimens, promotes glycogen repletion and prevents muscle damage. On the other hand, adequate intake of calories and total protein is essential to promote training adaptations in individuals aiming to increase muscle mass and gain weight (Jager, et. al., 2017).
Take Home Message
Athletes should aim to consume 1.6-2.0g/kg of protein daily what varies in terms of individual characteristic, volume and type of sport, and training status. As research progresses, recommendations are constantly updated and remember one size NEVER fits all.
Protein intake also varies in terms of nutritional goals
Recommendations for protein intake include 20-40g/meal or 0.25g/kg/meal of high biological value sources.
Both animal and plant based protein sources can meet your needs on a well-designed nutrition plan.
Alcock, R., Shaw, G., Tee, N. and Burke, L. (2019). Plasma amino acid concentration after the ingestion of dairy and collagen proteins, in healthy active individuals. Frontiers in Nutrition, (6), 143.
Jager, R., Kerksick, C., Campbell, B., Cribb, J., Wells, S., Skwiat, T., Purpura, M., Ziegenfuss, T., Ferrando, A., Arent, S., Smith-Ryan, A., Stout, J., Arciero, P., Ormsbee, M., Taylor, L., WIlbron, C., Kalman, D., Kreider, R., Willoughby, D., Hoffman, J., Krzykowsky, K., and Antonio, J. (2017). International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition. (14), 20.
Stark, M., Lukaszuk, J., Prawitz, A., and Salacinski, A. (2012). Protein timing and its effects on muscular hypertrophy and strength in individuals engaged in weight training. Journal of the International Society of Sports Nutrition. (9), 54. it comes to design, the Wix blog has everything you need to create beautiful posts that will grab your reader's attention. Check out our essential design features.