Muscle Protein Synthesis (MPS) and Protein Supplementation

Protein supplements can be very confusing. Questions that are often asked include: When do I take them? How many grams of protein do I need? What kind do I take? I'll go over the basics of protein supplementation in relation to exercise and how to use protein to maximize anabolic potential.

New research is coming out each year to help us understand the dynamics of protein usage around exercise.

First let's look at daily protein requirements. The Recommended Daily Allowance (RDA) for protein is 0.8g/kg, which is set by the Institute of Medicine. This is the amount that is required to maintain good health in normal people. For example, for a 180lb (81kg) male that equates to 65 grams of protein per day. This is equivalent to ~2 cups of chicken or about 8 eggs. However, exercise elevates these requirements. In a review of the literature (1) it was suggested that athletes and weightlifters need between 1.2 and 2.0 grams of protein per kg of body weight per day. Looking at the math, that puts a 180lb male at roughly 100 to 165 grams of protein per day. As you can see, that is significantly more than the RDA. It is also important to note that this is still less than the often rumored 1 gram of protein per lb of body weight.

It was first established that consumption of protein increases muscle protein synthesis (MPS) in 2001 (2). This study suggested that 30-40 grams of protein would be sufficient to achieve maximal stimulation of the anabolic muscle processes. This was during normal conditions, without the addition of exercise. It was later discovered resistance exercise also increases muscle protein synthesis regardless of protein supplementation, which ultimately results in an increase in lean body mass (3). A combination of protein consumption plus resistance exercise results in a synergistic stimulation of MPS. Indeed, the increase in MPS is thought to be an important factor in exercise induced muscle growth (5). This research has become the main reasons for the production of protein supplements.

There are multiple theories of when to take protein supplements. As mentioned above - protein before a workout increases anabolic processes, but that holds true for any time of day. Your body doesn't know that you're about to exercise. Research shows consumption of protein (10 grams per hour) during a workout can increase protein synthesis by about 35%. It's hard to determine whether this is an optimal dose, since only one study has been done using resistance exercise (9). Intraworkout protein supplementation may extend the window of opportunity during which the anabolic response to exercise can be facilitated. We don't currently know if intraworkout protein would translate to an increase in muscle mass over an extended training period (i.e., week/months) but the evidence hints that it might.

The next step is taking protein post exercise. It appears that as little as 10 grams post exercise will elicit an increase in muscle protein synthesis (6). One research group showed a two fold increase in MPS when subjects were given a supplement consisting of 10g protein, 8g carbs, and 3g fat. Yet, a more practical approach was taken by another research group. They gave subjects 500mL of fat-free milk post exercise (~17.5g protein, 25.7g carbs, 0.4g fat). After 12 weeks with 5d/week of resistance exercise they found a significant increase (+6%) in lean body mass and muscle fiber size. These two research papers are the foundation for including protein post exercise. Other research indicates that 20-25 grams of high-quality protein is sufficient to maximize the anabolic response to resistance exercise (10). Hence, there is no need for a 50 gram protein shake after a workout.

Notice that I haven't mentioned what type of protein is the best. It appears (from the study above) that milk contains some type of protein to maximally stimulate protein synthesis. Indeed, there are two types of protein in milk: whey and micellar casein. When researchers tried to tease out which of these two proteins was better they found that whey protein was superior. It caused a greater increase in MPS compared to soy protein and a carbohydrate drink (8). This translated to an increase in lean body mass of ~8lbs compared to the control group which also exercised.

One of the other frequently discussed topics is protein supplementation before sleep. Until recently there was no research to show that it helped facilitate muscle growth. However, in 2012 a study was published showing that casein ingested immediately before sleep is effectively digested and absorbed, thereby stimulating muscle protein synthesis and improving whole-body protein balance during post exercise overnight recovery (11). Specifically, they found that there was a 22% increase in muscle protein synthesis compared to the control group. Similar to the previously mentioned study on intraworkout protein supplementation, this was a short term study so it is not known whether this results in an increase in muscle mass over time, but it seems that may be true.

References

1. Wilson, Jacob, and Gabriel J. Wilson. “Contemporary Issues in Protein Requirements and Consumption for Resistance Trained Athletes.” Journal of the International Society of Sports Nutrition 3, no. 1 (June 5, 2006): 7. doi:10.1186/1550-2783-3-1-7.

2. Bohé, Julien, Aili Low, Robert R Wolfe, and Michael J Rennie. “Human Muscle Protein Synthesis Is Modulated by Extracellular, Not Intramuscular Amino Acid Availability: A Dose-Response Study.” The Journal of Physiology 552, no. Pt 1 (October 1, 2003): 315–24. doi:10.1113/jphysiol.2003.050674.

3. Phillips, S. M., K. D. Tipton, A. Aarsland, S. E. Wolf, and R. R. Wolfe. “Mixed Muscle Protein Synthesis and Breakdown after Resistance Exercise in Humans.” The American Journal of Physiology 273, no. 1 Pt 1 (July 1997): E99–107.

4. Biolo, G., S. P. Maggi, B. D. Williams, K. D. Tipton, and R. R. Wolfe. “Increased Rates of Muscle Protein Turnover and Amino Acid Transport after Resistance Exercise in Humans.” American Journal of Physiology - Endocrinology and Metabolism 268, no. 3 (March 1, 1995): E514–20.

5. Breen, L., and S. M. Phillips (2012). Nutrient interaction for optimal protein anabolism in resistance exercise. Curr. Opin. Clin. Nutr. Metab. Care 15: 226-232.

6. Levenhagen, Deanna K., Jennifer D. Gresham, Michael G. Carlson, David J. Maron, Myfanwy J. Borel, and Paul J. Flakoll. “Postexercise Nutrient Intake Timing in Humans Is Critical to Recovery of Leg Glucose and Protein Homeostasis.” American Journal of Physiology - Endocrinology and Metabolism 280, no. 6 (June 1, 2001): E982–93.

7. Moore, Daniel R., Meghann J. Robinson, Jessica L. Fry, Jason E. Tang, Elisa I. Glover, Sarah B. Wilkinson, Todd Prior, Mark A. Tarnopolsky, and Stuart M. Phillips. “Ingested Protein Dose Response of Muscle and Albumin Protein Synthesis after Resistance Exercise in Young Men.” The American Journal of Clinical Nutrition 89, no. 1 (January 1, 2009): 161–68. doi:10.3945/ajcn.2008.26401.

8. Tang, Jason E., Daniel R. Moore, Gregory W. Kujbida, Mark A. Tarnopolsky, and Stuart M. Phillips. “Ingestion of Whey Hydrolysate, Casein, or Soy Protein Isolate: Effects on Mixed Muscle Protein Synthesis at Rest and Following Resistance Exercise in Young Men.” Journal of Applied Physiology 107, no. 3 (September 1, 2009): 987–92. doi:10.1152/japplphysiol.00076.2009.

9. Beelen, Milou, René Koopman, Annemie P. Gijsen, Hanne Vandereyt, Arie K. Kies, Harm Kuipers, Wim H. M. Saris, and Luc J. C. van Loon. “Protein Coingestion Stimulates Muscle Protein Synthesis during Resistance-Type Exercise.” American Journal of Physiology. Endocrinology and Metabolism 295, no. 1 (July 2008): E70–77. doi:10.1152/ajpendo.00774.2007.

10. Beleen M, Burke LM, Gibala MJ, and Van Loon LJC. Nutritional strategies to promote postexercise recovery. J. Phys. Act. & Health 2010 20(6): 515-532.

11. Res, Peter T., Bart Groen, Bart Pennings, Milou Beelen, Gareth A. Wallis, Annemie P. Gijsen, Joan M. G. Senden, and Luc J. C. VAN Loon. “Protein Ingestion before Sleep Improves Postexercise Overnight Recovery.” Medicine and Science in Sports and Exercise 44, no. 8 (August 2012): 1560–69. doi:10.1249/MSS.0b013e31824cc363.