I Love Leucine: Protein Powder Absorption and Contribution to Muscle Synthesis +Recipes

By Connor Dawedeit

In the past several years, protein powders have exploded with popularity, and now you can hardly walk into a gym without passing several people walking out wielding shaker bottles. The allure of a drinkable, pure-protein snack replacement is hardly surprising, given the generally fat- and carbohydrate-phobic attitude of the average American, as well as the promises of the manufacturers of these supplements that they will generate a higher return on the investment of exercise in the form of muscle gain. However, it may hardly make sense that a powder dissolved in water and chugged post-exercise will endow the body with more anabolic potential; indeed, it almost seems akin to pseudoscience or even quackery. While the exact mechanisms by which protein powders exert their influence on the working of the body are still unclear, evidence has shown not only that protein powder consumption does indeed positively affect post-workout muscle synthesis, and that different varieties of protein may work more efficiently than others.

Protein powders are nothing more than purified, dehydrated forms of naturally synthesized protein, most often in the form of milk proteins (whey and casein) and soy; eggs and other plants are used for some brands but are not nearly as popular. Whey, casein, and soy are each considered complete protein sources; however, they differ in their rates of absorption and in the effects they produce in the body. Absorption rate is a key variable to consider when considering proteins, because rapidly absorbed proteins more readily provide usable amino acids to circulating plasma reserves, but a higher percentage of rapidly absorbed amino acids will be oxidized for energy before entering anabolic pathways. Whey protein induces a rapid yet short-lived spike in plasma amino acid levels, whereas casein absorption is much slower and prolonged, possibly as a result of delayed gastric emptying. The kinetics of soy protein falls between these two patterns of absorption, being absorbed and digested at an intermediate rate (according to a review written by an employee of Solae, a soy ingredients manufacturer).

In one study, differences in post-meal protein anabolism revealed consumption of a whey protein meal lead to a higher rate of post-meal protein synthesis than a casein-based meal (68% stimulation as opposed to 31%). Other groups have specifically observed and compared stimulation of post-exercise protein synthesis with whey, casein, and soy proteins. The rapid rise in free plasma amino acids induced by whey protein stimulates skeletal muscle anabolism more significantly than the gradual increase associated with casein intake. Evidence has shown that soy protein has been observed to stimulate muscle protein synthesis in a manner similar to whey protein, according to studies cited by the Solae review. The review further states that soy protein has been “overwhelmingly” demonstrated to have no impact on hormonal balances in humans. These differences are most likely attributable to absorption rates, as suggested by one which concluded that whey protein consumed in 20-minute “pulses” is not as effective at inducing muscle synthesis as when consumed in a single large bolus.

Interestingly, the results of one study show that consumption of whole-protein skim milk (containing both casein and whey proteins) leads to a more positive nitrogen balance in the body after exercise than does soy protein consumption, indicating higher amino acid bioavailability for use in anabolic pathways. Similarly, the Solae review states that a mix of rapidly- and gradually-absorbed proteins “more anabolic” than either consumption of soy protein or a mix of whey protein and free amino acids. These results suggest that whole-food consumption may be the most superior method of providing amino acids for muscle synthesis, making a case against the consumption of protein powders for use in bodybuilding and muscle gain. In fact, there are several drawbacks to usage of protein supplements; they tend to be relatively expensive, usually being sold in large containers costing around $30 or more. Some brands are heavily sweetened with sugar or artificial sweeteners, and can contain chemical additives, trans-unsaturated fatty acids, and even contaminants such as arsenic and lead at levels that could exceed safe levels for human consumption. Furthermore, one study measuring the contents of 20 different brands found that 4 powders produced in the USA and 7 produced in Brazil contained less total protein than advertised. It is important to research a protein powder supplement before purchasing it to ensure its contents reflect the contents of an individual’s healthy diet.

Protein powders are an easy addition to make to one’s diet, as they can be mixed into and consumed with just about anything. When using protein powder as an ingredient in a recipe, using an unflavored brand, which may likely have the added benefit of being unsweetened, might be best to avoid throwing off flavor. A single powder or a mixture of 2 or more may be used, depending on your preference. Possibly the easiest method is to add the powder to a smoothie. This is a great way to simultaneously add more fruits and dairy to one’s diet. Bags of frozen fruit are relatively cheap, and you can change what you have on hand often for variety. The downside of this method is that it requires a blender, which can be expensive, takes up space, and is too loud to use first thing in the morning.



Protein-Enhanced Fruit Smoothie Recipe

  • 1 cup frozen fruit(s) of choice
  • 1 cup dairy (2% milk, kefir, Greek yogurt) or nondairy milk (almond, cashew, or soymilk)
  • 1 banana (this is a great way to use old bananas with an unappealing, mushy texture) Water, as needed to make the smoothie liquid enough to blend if necessary 1 serving protein powder of choice

Blend all ingredients together, adding the liquids to the blender first, then the powder, then the fruit. This will help ensure the powder blends into the smoothie instead of being flung up on to the lid. Consume immediately (smoothies are difficult to prepare well in advance as they tend to separate over time). If you don’t own a blender or prefer baked snacks to drinkable fruit, try a recipe for baked protein balls or oat bars, such as the following, from ifoodreal.com and nutritionistinthekitch.com, respectively.

Coconut Protein Balls

  • 3 cups dates, pitted
  • 120g protein powder(s) of choice
  • ¼ cup carob or chocolate chips
  • 1½ cup almonds
  • 2 tbsp cocoa powder, unsweetened
  • ½ cup warm water
  • ⅔- 1 cup coconut flakes, unsweetened

Combine dates, almonds and water in a food processor and grind. Small chunks are fine. Add to the mixing bowl along with protein powder, carob chips and cocoa powder. Mix with spatula until well combined. Mixture will seem dry in the beginning. If necessary add more water. Spread coconut flakes on a flat surface like a dinner plate and roll 32 balls in it. Makes ~15-30 servings (121 calories and 5.5g protein per ball).

GF Gingerbread “Proatmeal” Bake

  • 1½ cups gluten free rolled oats
  • 2 scoops (½ cup) natural vanilla protein powder (gluten free if needed)
  • ¼ cup ground flaxseed
  • ¼ cup coconut palm sugar
  • 1 teaspoon baking powder
  • 1 teaspoon ground ginger
  • 1 teaspoon cinnamon
  • 1 egg, beaten
  • 3 tablespoons unsulphured molasses
  • 1½ cups unsweetened almond milk (or other milk of choice)
  • 1 tsp pure vanilla extract
  • ¼ cup raisins
  • ¼ cup chopped dates

Preheat the oven to 375 degrees. In a large bowl combine the dry ingredients, except for the coconut palm sugar. In another bowl, whisk the egg and add in the wet ingredients as well as the coconut palm sugar. Add the wet ingredients to the dry and stir to combine. Fold in the raisins and the dates. Line an 8×8 or 9×5 inch pan with parchment paper. Pour batter into pan. Bake for about 25 – 30 minutes or until a toothpick pulls clean from the center of the pan.



1. Paul, G. (2009, August). The Rationale for Consuming Protein Blends in Sports Nutrition. J Am Coll Nutr, (28): sup4, 464S-472S. DOI: 10.1080/07315724.2009.10718113

2. Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, & Beaufrére B. (1997, December 23). Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci USA (94)26: 14930 – 14935

3. West D, Burd N, Coffey V, Baker S, Burke L, Hawley J, et al. (2011, July 2011). Rapid aminoacidemia enhances myofibrillar protein synthesis and anabolic intramuscular signaling responses after resistance exercise. Am Soc for Nutr 94(3): 795 – 803. DOI: 10.3945/ajcn.111.013722

4. Wilkinson S, Tarnopolsky M, MacDonald M, MacDonald J, Armstrong D, & Phillips S. (2007, April). Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. Am J Clin Nutr 85(4): 1031 – 1040.

5. Tarantino O. The Best and Worst Protein Powders. Retrieved from http://www.eatthis.com/protein-powders

6. Consumer Reports. (2010, July). Health Risks of Protein Drinks. Retrieve from http://www.consumerreports. org/cro/2012/04/protein-drinks/index.htm

7. Almeida C, Alavares T, Costa M, Conte-Junior C. (2015). Protein and Amino Acid Profiles of Different Whey Protein Supplements. J Diet Suppl 13(3): 313-323. DOI 10.3109/19390211.2015.1036187

8. Coconut Protein Balls Recipe. Retrieved from http://ifoodreal.com/workout-snack-coconut-protein-balls- recipe/

9. GF Gingerbread “Proatmeal’ Bake. Retrieved from http://www.nutritionistinthekitch.com/gf-gingerbread -proatmeal-bake/


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