By Isaac Mourier
Protein is a key macronutrient used as a building block within several processes in the body including immunity, restoration and rebuilding of tissue, hormone production, growth, and oxygen transport. Despite the importance of adequate protein intake, a lot of ambiguity remains around appropriate recommendations, which often leaves athletes questioning: How much protein is enough? How much is too much? When should I be eating protein? I follow a vegan diet; what are my options?
Understanding protein needs and meeting requirements are essential in assisting adaptations to both endurance (1) and strength training (2). Much like carbohydrate, protein recommendations are dependent on many factors including the type, duration and intensity of exercise. Protein requirements may vary at different junctures in the season and during different phases of training. Understanding individualized requirements is crucial when fueling for performance. Furthermore, recognizing the importance of protein quality for athletes following both animal-based and plant-based diets is a necessity.
Initial literature supported providing protein recommendations based on an athlete’s chosen sport/activity. However, research now shows that protein recommendations should be given as a range and be based around optimal adaptation to specific sessions or periods of training. The vast majority of athletes will fall into the range of 1.2 – 2.0g/kg/bw (around 98 – 165g protein for a 180lb athlete, as there are 2.2 lbs per kg). The lower end of the range should be used for activities with a lower musculoskeletal load or during periods of lower intensity training, while the higher end of the range is applied to muscle-damaging exercise, high-intensity sessions, and during periods of a calorie deficit (2). Daily protein intake should be split into multiple meals and snacks (e.g. 25% daily protein in each meal and 10-15% of daily protein per snack) and should be consumed every 3-4 hours throughout the day. This allows there to be a consistent supply of amino acids to the muscle, maximizing muscle protein synthesis and keeping muscle protein breakdown to a minimum.
Timing of ingestion:
It is well documented that exercise and macronutrient ingestion interact synergistically to provide better results than either exercise or nutrition alone. This is namely due to the increased amino acid sensitivity following exercise, resulting in an enhanced protein uptake and subsequent improvements on recovery and adaptation (3). Following exercise, protein synthesis rates peak within 3 hours and remain elevated for 24-72hrs post-exercise (4). Therefore, paying attention to the timing of protein intake throughout the day and in relation to exercise can play a critical role in recovery and subsequent performance. When an athlete has less than 24hrs to recover, it is recommended to consume 0.25 – 0.3g/kg/bw (15-40g) of high-quality protein in the acute recovery phase (0-2hrs) following exercise (5), with some studies showing that a maximum dose of up to 40g may provide further benefits (6). However, if there is not a subsequent training session within 24hrs, new research shows that meeting daily protein requirements should be adequate to support recovery and adaptation, and utilizing the acute recovery phase is less important (7). Proteins are made up of organic compounds called amino acids, some of which can be synthesized by the body (termed non-essential), and others which cannot be synthesized (termed essential amino acids or EAA’s). The amount of protein consumed post-exercise should contain at least 10g of EAA’s, which translates to roughly 15g of high-quality protein e.g. 8oz chocolate milk plus 1oz beef jerky (5). Furthermore, as mentioned previously, consuming 0.25 – 0.3g/kg/bw (15-40g) of high-quality protein every 3 – 4 hours throughout the day will help to maintain a plentiful ‘pool’ of amino acids and create an ideal environment for recovery and adaptation to occur.
Protein quality is often distinguished by a food’s essential amino acid composition and the bioavailability of the contained protein (how much of the consumed protein can be absorbed). A food product containing all of the EAA’s is known as a complete protein, whereas a food product that is missing one or more EAA is considered an incomplete protein. When talking about high-quality protein sources, this generally refers to complete proteins. The best sources of EAAs are animal proteins, like eggs, meat, and milk, while most plant proteins lack one or more EAA, decreasing their protein quality. The superiority of many animal proteins when compared to plant-based proteins can be attributed to higher delivery of EAA’s and branched-chain amino acids (BCAA’s) to the muscle (8). High-quality protein sources e.g. whey protein derived from dairy products, have been shown to be superior in stimulating muscle protein synthesis when compared with equal amounts of lower quality protein sources e.g. soy protein. Think of protein like a jigsaw puzzle that requires all of its pieces in order to be completed. Having said this, athletes following a plant-based diet can consume adequate levels of EAA by meeting their daily protein requirements through a variety of plant-based protein sources e.g. beans, lentils, nuts, and soy, which each contain different quantities of EAAs. This will ensure that all nine EAA’s are present in the body to support recovery and adaptation.
The BCAA leucine is also an important aspect of protein quality as 2 – 3g of leucine has been shown to directly activate the mechanistic target of rapamycin complex 1 (mTORC1), turning on the primary pathway for muscle recovery and growth in the body. While adequate post-exercise leucine consumption will result in stimulation of muscle protein synthesis, without an ample pool of EAA’s, muscle protein synthesis can be ‘switched on’ but not ‘sustained’. To achieve muscle recovery and adaptation, adequate quantities of both leucine and the other 8 EAA’s is necessary (2).
Although meeting recommendations through whole food sources is always the preferred choice, supplements can be a quick and easy way to assist an athlete with meeting their needs. When it comes to post-workout supplements, whey protein contains the highest amount of leucine per volume (10.9%), and soy (whey’s plant-based brother and a vegan option) contains around 8%. Both of these sources are highly digestible and have comparative qualities when amino acid content is matched. However, to do this it is required to adjust the dose of soy e.g. 40g of soy protein contains around the same amount of leucine and essential amino acids as 25g whey (9). In supplement form, both whey and soy protein are commercially available in a number of ways. Most commonly, these products are sold as a powder, but they are also integrated within shakes, smoothies, yogurts and bars.
In summary, the key to enhancing recovery is to maximally stimulate and sustain muscle protein synthesis, while limiting periods of muscle protein breakdown. This can be achieved by paying attention to the timing, quantity and quality of protein sources. Athletes are recommended to consume between 1.2 – 2.0g/kg/bw per day with the amount dependent on their daily physical requirements. When training will take place again within 24hrs, it is suggested to consume between 20 – 30g (up to 40g) of high-quality leucine-rich protein within 2 hours of exercise. Furthermore, daily protein intake should be spread out at regular intervals throughout the day (every 3-4 hours). These recommendations can be met regardless of an athlete’s dietary preferences, and there are many good options for athletes to choose from e.g. both plant-based and animal sources. Athletes should always aim to meet protein recommendations through a variety of nutrient-rich food sources, however, protein supplements may be a valuable addition to their diet due to convenience. Whey protein is the highest quality and most easily digested, but soy protein seems to be the most comparable plant-based protein.
- Moore, D., Camera, D., Areta, J. and Hawley, J., 2014. Beyond muscle hypertrophy: why dietary protein is important for endurance athletes. Applied Physiology, Nutrition, and Metabolism, 39(9), pp.987-997.
- Jager, R., Kersick, C.M., Campbell, B.I., Cribb, P.J., Wells, S.D., Skwiat, T.M., Purpura, M., Ziegenfuss, T.N., Ferrando, A.A., Arent, S.M., Smith-Ryan, A.E., Stout, J.R., Arciero, P.J., Ormsbee, M.J., Taylor, L.W., Wilborn, C.D., Kalman, D.S., Kreider, R.B., Willoughby, D.S., Hoffman, J.R., Krzykowski, J.L., and Antonio, J. (2017) International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition, 14 (20), https://doi.org/10.1186/s12970-017-0177-8.
- ACSM (2016) Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise, 48 (3), pp. 543 – 568.
- Biolo, G., Gastaldelli, A., Zhang, X.J., and Wolfe, R.R. (1994) Protein synthesis and breakdown in skin and muscle: a leg model of amino acid kinetics. American Journal of Physiology, 3 (267), pp. 467 – 474.
- Burd, N., West, D., Moore, D., Atherton, P., Staples, A., Prior, T., Tang, J., Rennie, M., Baker, S. and Phillips, S. (2011). Enhanced Amino Acid Sensitivity of Myofibrillar Protein Synthesis Persists for up to 24 h after Resistance Exercise in Young Men. The Journal of Nutrition, 141(4), pp.568-573.
- Phillips, S. (2012). Dietary protein requirements and adaptive advantages in athletes. British Journal of Nutrition, 108(2), pp.158-167.
- Schoenfeld, B., Aragon, A. and Krieger, J., 2013. The effect of protein timing on muscle strength and hypertrophy: a meta-analysis. Journal of the International Society of Sports Nutrition, 10(1).
- Rindom, E., Nielsen, M., Kececi, K., Jensen, M., Vissing, K. and Farup, J., 2016. Effect of protein quality on recovery after intense resistance training. European Journal of Applied Physiology, 116(11-12), pp.2225-2236.
- Gorissen, S., Crombag, J., Senden, J., Waterval, W., Bierau, J., Verdijk, L. and van Loon, L., 2018. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids, 50(12), pp.1685-1695.