Protein is the name of the game when it comes to building muscle. When you think of protein, do visions of meat and dairy come to mind? Both meat and dairy are complete sources of protein, meaning they contain all the essential amino acids your body needs but can’t make.
In contrast, plant-based protein sources of protein typically lack one or more essential amino acids. For example, rice protein has an abundance of methionine and cysteine but lacks lysine. In contrast, legumes are a good source of lysine but are low in methionine. So, most plants fall short in one or more essential amino acids. An exception is soy protein. Soy is a complete protein, meaning it contains each essential amino acid your body needs in sufficient quantities.
Can You Build Muscle Without Animal Protein?
It is possible to build muscle on a completely plant-based diet. But, it takes careful planning to ensure that you’re getting enough protein and all the essential amino acids. You can do this by eating a variety of plant-based protein sources in sufficient quantity and that means consuming enough calories as well. In fact, there are a number of well-known vegan bodybuilders.
On the other hand, meat and dairy protein rank higher than plant protein on the protein quality scale. One way scientists measure the quality of a protein is using a test called the protein digestibility corrected score. (PDCAAS) Another test of protein quality is called the digestible indispensable amino acid score. (DIAAS).
When you look at the DIASS scores for animal vs. plant protein sources, meat, eggs and dairy rank close to 100%. in contrast, plant-based foods clock in at around eighty or below. So, animal-based protein sources are deemed higher quality as they better absorbed and more bioavailable.
So, animal-based protein has some advantages, but is meat or dairy more effective at boosting muscle protein synthesis? A study published in the American Journal of Clinical Nutrition looked to see if one had an advantage over the other. As mentioned, they’re both a source of complete protein with similar DIASS scores. This study showed that both meat and dairy protein are equally proficient at stimulating muscle protein synthesis. So, one doesn’t have a clear advantage over the other and both have some advantages over plant-based protein.
Differences Between Plant-Based and Animal Protein
As mentioned, plant-based protein lacks one or more essential amino acids, but you can make up for this shortfall by consuming more protein from a diversity of sources. Choose plant protein options like beans, lentils, nuts, whole grains, and seeds. Even vegetables have some protein. But, plant protein also compares unfavorably with animal protein in terms of digestibility. Scientists determine this by feeding protein to a subject and seeing how much of the nitrogen from that protein ends up in the feces. More nitrogen enters the feces from plant-based protein as opposed to animal-based sources.
In general, plant-based protein is lower in the amino acid leucine, a branched-chain amino acid. Research shows that leucine is the “head honcho” when it comes to activating the mTOR pathway, the major pathway for muscle protein synthesis. But, you can get enough leucine from plant-based foods if you consume enough of them. Soy-based foods are particularly high in leucine. In fact, soy contains slightly more leucine per 100 grams than beef. Nuts and beans are a decent source as well.
Plant-Based Protein Has Other Health Benefits
If you only look at the anabolic potential of animal-based protein, you might conclude meat and dairy are the best options for the dinner table. However, research links plant-based sources of protein with a lower risk of cardiovascular disease, hypertension, type 2 diabetes, obesity, and some types of cancer. In other words, plants are good for your overall health – and we know how important being healthy is!
Plus, the Western diet is deficient in fiber, and if you focus mainly on animal-based food, you would almost surely fall short on fiber. Fiber increases satiety as well, so it helps with appetite control and, potentially, with weight loss. Then, there are environmental issues to consider. Producing meat increases greenhouse gas emissions more than growing plants for food consumption. So, when you look at the issue as a whole, there are lots of reasons to consume more plants.‘
The Bottom Line
In terms of activating muscle protein synthesis, meat and dairy top plant protein, although you can compensate by eating more plant protein, consuming enough calories, and eating a variety of plants. No point in splitting hairs over meat versus dairy protein as both turn on the synthesis of muscle proteins to a similar degree. For overall health and the environment, consuming more plant-based protein is favorable. The key is to find the right balance that’s right for you and your health and fitness goals. But, get your protein from healthy, whole food sources rather than protein powders and supplements.
If you’re eating a solely plant-based diet, consider adding soy foods to your diet, as soy is highest in the amino acid leucine. Soy contains some anti-nutrients that reduce the absorption of some minerals, but this is unlikely to be a problem if you’re eating a balanced diet or unless you’re eating soy at every meal. Fermenting soy reduces anti-nutrients, so tempeh, a type of fermented soy, is a good choice. If you have an underactive thyroid, consider limiting soy foods as the contain goitrogens that may interfere with thyroid function. Make sure you’re consuming enough iodine as well. Keep in mind, the risk of interfering with thyroid function if you have an underactive thyroid by eating soy is somewhat theoretical and is unlikely to be a problem unless you consume a diet low in iodine.
The take-home message? Find what balance of animal and plant-based protein works for you! We’re all a bit different, but we all have the same goal in mind – to be as fit and healthy as possible.
References:
Proc Nutr Soc. 2018 Feb;77(1):20-31. doi: 10.1017/S002966511700194X. Epub 2017 Aug 29.
Today’s Dietitian. Vol. 19, No. 2, P. 26, (February 2017)
Canadian Journal of Plant Science, 1980, 60(4): 1327-1331, https://doi.org/10.4141/cjps80-187.
My Food Data. “Top 10 Foods Highest in Leucine”
Thyroid. 2006 Mar;16(3):249-58.
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