Protein Quality For Muscle Building: Animal vs. Plant-Based Sources
Updated: Feb 8
With the rise in popularity of plant-based proteins, athletes are asking themselves whether this will provide them with the same benefits as animal-based proteins. Let’s take a look at why protein is important and how 2 popular animal-based proteins stack up against the more environmentally sustainable plant-based proteins.
Muscle turnover (the cycle of replacing broken down proteins with new proteins) occurs at 1-2% per day, leaving room for either muscle loss or muscle synthesis. When focusing on the latter, it is important to consider both dietary protein and physical activity. Physical activity, specifically, resistance training works by increasing the synthesis of muscle protein. However, nutritional considerations will help you capitalize on the anabolic effects of resistance training. For increasing lean body mass, it is recommended to consume 1.6-2.2 g protein/kg body weight to complement your exercise regimen, and this should be divided into ~20-40 g protein doses (or 0.4g/kg body weight) throughout the day.
Proteins are chains of varying types and amounts of amino acids linked together. There are 9 essential amino acids (EAA) found in foods that our bodies don’t make on their own. All of these EAAs are needed to maximally stimulate muscle protein synthesis. There is one amino acid in particular that triggers or turns on muscle protein syntheses; that amino acid is Leucine. Amino acids that are derived from plant-based protein sources, such as pea protein or soy protein, have been shown to have a lower capacity to stimulate a skeletal muscle response than that of animal-based sources. One reason for this is because plant-based protein sources contain fewer essential amino acids. These essential amino acids cannot be made inside your body, and thus they must be obtained through dietary sources. Having all essential amino acids present in sufficient amounts is needed for optimal muscle protein synthesis. Leucine tends to be lower in plant-based proteins compared to animal protein. However, there are some plant-based proteins that happen to contain large amounts of leucine. Corn is number 1, followed by potato, pea, and brown rice. Unfortunately, these foods in their whole food form don’t contain much protein, but when the protein is isolated, we can get large amounts of protein and essential amino acids. Pea and brown rice protein powders are a popular protein source for vegan protein powders. Whey protein has the highest leucine content of the animal proteins, followed by milk, and then casein. It is likely due to this high leucine content in whey protein that accounts for its larger capacity to stimulate muscle protein synthesis. Another factor that is useful for older individuals to keep in mind is that aging muscles begin to require more leucine to achieve the same rates of muscle protein synthesis.
Protein digestibility is another factor that plays a role in the ability to stimulate muscle protein synthesis. This refers to the amount of a protein that gets broken down and absorbed by the body in a form that is suitable for the body to use towards protein synthesis. Animal-based protein sources, such as whey and casein, are ~90% digestible. However, plant-based sources have a lower digestibility value ranging from 45-80%. The lower the digestibility value, the less skeletal muscle response in the body.
Is whey protein the best choice because it has the highest amount of EAAs and leucine? Whey is great because it’s straight forward – it is a rich source of EAAs, a high leucine content, and you can use smaller amounts of protein compared to plant-based protein and get the same benefit. However, does that mean whey (or other animal protein) is the best option? From a muscle building standpoint, you can get similar amounts of muscle protein synthesis from plant-based protein if you eat enough of them. For example, it has been shown that with larger amounts of plant-based proteins (>30 g/meal) consumed, comparable responses to muscle protein synthesis as with animal-based proteins will take place. Another method to maximize the effects of plant-based protein on muscle protein synthesis might be to combine complementary protein blends. For example, soy and pea proteins are low in methionine and higher in lysine, while hemp and brown rice proteins are high in methionine and lower in lysine. In this case, combining these two protein sources together would help to achieve adequate amounts of both essential amino acids. Some protein powders already have these 2 sources blended, like the Orgain Sport Protein Powder, which blend brown rice and pea proteins. For those that don’t tolerate milk-based proteins, vegan proteins in the right amounts can give you a similar benefit. Two added bonuses are that 1) plant proteins are more environmentally sustainable and 2) persons who limit animal protein have lower risk of several diseases, such as cancer and heart disease. Whether you choose whey, milk, casein, pea, or brown rice, keep in mind that you can get a similar muscle building effect from them all as long as you’re using the right amounts and the right blend of amino acids.
1) van Vliet S, Burd NA, van Loon LJ. The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption. J Nutr. 2015 Sep;145(9):1981-91. doi: 10.3945/jn.114.204305. Epub 2015 Jul 29. PMID: 26224750.
2) Gorissen SHM, Witard OC. Characterising the muscle anabolic potential of dairy, meat and plant-based protein sources in older adults. Proc Nutr Soc. 2018 Feb;77(1):20-31. doi: 10.1017/S002966511700194X. Epub 2017 Aug 29. PMID: 28847314.
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