Plant Based Proteins and Muscle Protein Synthesis

Morgan King

MSc, RD

            Vegetarianism and veganism dietary patterns have been around for a long time and have been gaining popularity among the athletic population. A recent study collected information on the prevalence of vegan and vegetarian athletes in endurance runners. From that study, 34% and 20% of athletes were vegan and vegetarian, respectively (1).

While it is not impossible to excel in sports and be vegetarian/Vegan there are just some limitations regarding protein synthesis that need to be addressed when switching to a plant-based diet that restricts or eliminates food groups. These two limitations come down to protein quality and availability of nutrients. These limitations are overcome with strategies such as increasing volume and maximizing food variability

What makes plant proteins different?

Problem # 1 Protein Quality

Most plant-based foods have protein but are considered incomplete proteins, meaning they do not contain all essential amino acids (building blocks for protein). There are some plant foods exceptions, such as soy or soy products, quinoa, buckwheat, or spirulina that are considered almost complete proteins. Foods such as chickpeas, lentils, beans, and tempeh are incomplete protein sources. However, having an incomplete set of protein amino acids can easily be overcome by pairing. Pairing is a fancy term for mixing different plant foods in the same meal to create a complete protein source (2). A classic example would be combining beans and rice which grouped in a meal provide all the essential amino acids. In short, combining an incomplete plant-based protein needs to be paired with a grain (E.g. pasta, rice, crackers, bread) or nuts/seeds to be considered complete. Getting all the building blocks in plant-based food is easily achievable but requires an understanding of building a balanced diet.

Problem # 2 Availability

Many dietitians suggest vegans and vegetarians eat larger food portions for a plant-based diet.  This is because of the issues with digestibility and absorption. Plant-based foods have high amounts of fibre (which is great for your gut)  and anti-nutrients that can bind nutrients found in the plants and reduce the available nutrients for us to absorb into our bodies. However, the issue with the binding of nutrients can be overcome by cooking plant-based foods (2). Cooking food can significantly reduce the anti-nutritional and fibre effects and increase nutrient availability (3). If you don’t want to cook some foods, the other way around the decreased nutrient availability is to increase the volume of food you are consuming. Increasing the volume of plant-based foods can be challenging though, especially since fibre significantly increases the feeling of fullness and often reduces the overall intake of food.

Why does this apply to muscle protein synthesis?

Following exercise there is a breakdown of muscle tissue which is built back through consuming foods with protein. To build muscle you need to have all the amino acid building blocks, and leucine amino acid gets a lot of attention because of its ability to stimulate muscle protein synthesis (the process of rebuilding muscles). To maximize muscle building you need about 3g of leucine amino acid and 20-25g of protein to get this amount. Still, the one main concern is that plant-based protein foods are lower in an amino acid, leucine.

It has been shown especially for muscle protein synthesis, that whey (milk protein powder) results in better muscle synthesis compared to plant-based proteins. The larger increases in muscle synthesis are attributed to whey proteins’ high concentration of leucine. Whey contains considerably more leucine compared to plant-based foods such as soy, lentils, and beans (4). The only similar food to whey protein (but still not the same) is soy or soy products. A Jeukendrup shows an excellent graph that demonstrates varying amounts of leucine in animal vs. plant-based linked here. So, athletes that limit or do not include dairy or dairy products or have low intakes of soy would have lower intakes of leucine and as a result, muscle building is not maximized.

Remember how I mentioned that pairing can improve the quality of plant-based proteins? Well, what if you were to make a supplement that contains a pairing match that has a similar composition to whey protein? This brings us to an interesting article by Teixeira F et al (2022) recently published a comparison study between the intake of plant-based (mixture of pea protein isolate & yeast protein) and whey supplements on sports performance with semi-professional futsal players. The authors then matched the plant-based supplement to a whey protein nutritional composition.

The plant-based supplement was equivalent in

-           Energy

-           Nitrogen

-           And importantly leucine content

 And from their findings, the authors reported that there were NO differences between the groups for gaining muscle or strength. From a research perspective that would be the expected outcome because the composition of the groups are similar. Teixeira et al bring up a great point when discussing the comparisons of the other studies with paired protein supplements in which a lot of them are not matched in the leucine content and therefore would result in less muscle gain and strength.

It will be interesting to see the development of paired plant-based supplements and whether these supplement give similar effects as eating whey protein for vegetarian/vegan athletes. This is the first study that has shown that there were no differences and as always, more research is needed to make recommendations.  

 References

1. Wirnitzer, K.; Tanous, D.; Motevalli, M.; Wirnitzer, G.; Leitzmann, C.; Pichler, R.; Rosemann, T.; Knechtle, B. Prevalence of Female and Male Vegan and Non-Vegan Endurance Runners and the Potential Associations of Diet Type and BMI with Performance—Results from the NURMI Study (Step 1). Nutrients 2022, 14, 3803. https://doi.org/10.3390/nu1418380

2. 2. Nichele S, Phillips S, Boaventura B. Plant-based food patterns to stimulate muscle protein synthesis and support muscle mass in humans: a narrative review. Applied Physiology, Nutrition and metabolism, 2022, 47(7): 700-710. 

3. Berrazaga, Insaf, et al. "The role of the anabolic properties of plant-versus animal-based protein sources in supporting muscle mass maintenance: a critical review." Nutrients 11.8 (2019): 1825.

4. Jeukendrup A. What is the best protein source for muscle building. My sport science. https://www.mysportscience.com/post/2017/11/03/what-is-the-best-protein-source-for-building-muscle

5.  Teixeria, F, Matias C, Faleiro J, et al… Schoenfeld B. A Novel plant-based protein has similar effects compared to whey protein on body composition strength, power, and aerobic performance in professional and semi-professional Futsal players. 2022, 934438 (9), frontiers.