Manav Bajaj, Sport Nutritionist
While it is now common understanding that protein helps muscle building/growth which is essential for athletic performance. However, in the current world of protein supplements there is a large variety of options available ranging from dairy and animal based proteins (whey, casein, milk, beef) and vegetarian friendly options such as plant based proteins (soy, pea, quinoa, wheat).
However, there is still one question that is unanswered to an extent – Do different proteins from different sources differ in their capacity to promote muscle growth? And if so, then which is the best source of protein?
To understand the difference between protein sources, a good understanding of what constitutes a complete protein source is needed. A complete protein source consists of 20 amino acids, of which 11 are termed as essential amino acids (EAA) meaning they cannot be synthesized in the body and one must consume these from their diet and 9 are termed non-essential amino acids (NEAA) and these can be synthesized within the body. There are three amino acids that differ slightly in their peptide bonds and are termed Branched chain amino acids (BCAAs) which contain the amino acids – Leucine, Isoleucine and Valine. Leucine is considered to be the amino acid that triggers muscle protein synthesis (MPS) which is the process of rebuilding muscle fibers (Atherton et al. 2017). The major difference between plant-based proteins and dairy and animal-based proteins is their EAA content, more specifically Leucine content. Plant-based proteins generally have a leucine content of 6-8% while dairy and animal-based proteins have a leucine content of 8-13% (Van Vliet et al. 2015). Another difference between plant-based and dairy and animal-based proteins is the digestibility via the small intestine. Plant based proteins are also generally deficient or have very low levels of at least 1 EAA – generally lysine and methionine. Supplement companies are now starting to fortify plant-based proteins with lysine and methionine but this impacts the digestibility. In fact, dairy and animal-based proteins such as whey and casein are the only proteins that boast a higher EAA amino acid content that human muscle itself.
Here is a graph comparing the EAA and leucine content of animal-based proteins to plant-based proteins.
So, what is in it for the vegetarian athlete?
There are exceptions, however, such quinoa based protein which boasts a leucine content of 12% and an EAA content that is higher than most dairy and animal based proteins (Thanapornpoonpong et al. 2008). Therefore, consuming quinoa can be a good strategy to combine with a plant based protein to have a higher overall leucine content.
In conclusion, this article aimed to verify whether there are any differences between various types of protein and whether those differences in characteristics can affect the efficacy of said protein source. While current research suggests that dairy and animal based proteins are superior to plant-based proteins owing to their higher digestibility and EAA content. However, it does not mean that vegetarian athletes or athletes who prefer plant based protein sources are at a disadvantage because they can enhance the leucine content by following measures like incorporating high leucine foods like quinoa or opting for quinoa based proteins which have a high EAA content.
Atherton, P., Kumar, V., Selby, A., Rankin, D., Hildebrandt, W., Phillips, B. and Smith, K. (2017) Enriching a protein drink with leucine augments muscle protein synthesis after resistance exercise in young and older men. Clinical Nutrition, 36 (3), 888-895.
Van Vliet, S., Burd, N. and Van Loon, L. (2015) The Skeletal Muscle Anabolic Response to Plant-versus Animal-Based Protein Consumption1. The Journal of nutrition, 145 (9), 1981-1991.
Thanapornpoonpong, S., Vearasilp, S., Pawelzik, E. and Gorinstein, S. (2008) Influence of various nitrogen applications on protein and amino acid profiles of amaranth and quinoa. Journal of agricultural and food chemistry, 56 (23), 11464-11470.