Finishing a workout by downing a protein shake has become an almost mandatory ritual for avid gym goers in recent years, but do we really need to supplement with protein, and why?
First we need to look at where protein comes from and what its role is in the human diet. Dietary protein generally comes from meat, fish, dairy products and eggs, as well as some vegetable sources although this is in lower concentrations. As one of the three Macronutrients (Protein, Carbohydrates and fats), protein provides 4kcals of energy per gram. Functions of protein within the body include; growth and repair of tissue, hormone and enzyme production, formation of cell structure and as an energy source (Lemon, 1997).
Proteins are essential Nitrogen compounds made up from amino acids, these can be broadly categorised as non-essential (produced in the body) and essential (required from exogenous sources).
Since protein is turned over on a daily basis, degradation and intake must be balanced in order to maintain our current level of stored protein (muscle mass). This is known as nitrogen balance. A negative nitrogen balance leads to a catabolic environment and reduction in muscle mass, whereas a positive nitrogen balance leads to an anabolic state and increased muscle mass (Carbone, McClung, & Pasiakos, 2012). Obviously the latter is more desirable for those seeking to improve body composition and recover from bouts of strenuous exercise.
Daily recommendations for protein intake vary depending on goals and activity level, from 0.8g per kg of body mass for general populations (Institute of Medicine, 2005), up to >2g per kg for heavy strength trained athletes. Individual requirements will obviously vary, however most active people will find 1.2-1.8g per kg/d sufficient (Phillips, 2012). Whilst these levels are fairly achievable with a normal diet containing plenty of high quality protein based food, timing can also be an issue.
Due to muscle protein synthesis being up-regulated following exercise, the body is in a situation where it is able to process increased amounts of protein and use it to repair and grow muscle tissue. Whilst studies have found individual variation, this ‘anabolic window’ is thought to last for around 2-3 hours, gradually decreasing from the end of a workout (Phillips & Van Loon, 2011). As such, consuming a high quality, quickly absorbed protein source during this period is advantageous.
Whey protein is ideal for this purpose, as it is rapidly absorbed and available in the form of an easily digestible shake. Consuming a shake containing 20-25g of protein in the form of whey, has been shown to optimally stimulate muscle protein synthesis (MPS), more than this has not been shown to further increase MPS (Koopman, 2011).
In summary, protein is an essential macronutrient, which can be obtained in satisfactory amounts through a good diet. For active individuals or those seeking to increase muscle mass or recovery, supplementation with high quality whey protein in the post-workout period may be beneficial.
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References
Carbone, J. W., McClung, J. P., & Pasiakos, S. M. (2012). Skeletal muscle responses to negative energy balance: effects of dietary protein. Advances in Nutrition, 3, 119–26.
Institute of Medicine. (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). National Academy of Sciences.
Koopman, R. (2011). Dietary protein and exercise training in ageing. The Proceedings of the Nutrition Society, 70, 104–13.
Lemon, P. W. R. (1997). Dietary protein requirements in athletes. The Journal of Nutritional Biochemistry, 8, 52–60.
Phillips, S. M. (2012). Dietary protein requirements and adaptive advantages in athletes. British Journal of Nutrition, 108, 158–167.
Phillips, S. M., & Van Loon, L. J. C. (2011). Dietary protein for athletes: From requirements to optimum adaptation. Journal of Sports Sciences, 29, 29–38.