Protein is Power
By: Erica Batad, Undergraduate Student in Dietetics & Nutrition at the University of Illinois Urbana-Champaign.
Photo by Pexels/Vanessa Loring
One of the most common misconceptions about a plant-based diet is that you cannot get enough protein from plant foods. While some animal protein may contain higher quantities of essential amino acids, which will be discussed later in this post, plant protein sources can still provide the body with necessary amounts of protein.
Why is protein important
Protein is one of the most vital compounds needed for human nutrition. Not only does protein help build muscle tissue, but it regulates metabolic pathways, aids in satiation, and provides immunity by producing antibodies. Everyone’s recommended intake for protein may be different as it varies by age, gender, physical activity, and quality of the source of protein. Plant-based sources of protein have been found to benefit the human body in that it can manage blood pressure, reduce cholesterol levels, and reduce the risk for coronary heart disease. (1)
Breakdown of protein
Protein is composed of 20 different amino acids. There are 9 essential amino acids that can’t be made by the body and therefore need to come from food. These essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The rest of protein is made up of 11 non-essential amino acids which means the body can produce these amino acids even if it does not come from food. These non-essential amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
A deficiency in the essential amino acids can lead to many health issues including but not limited to low appetite, insomnia, anemia, fatigue, weakness, weight loss, oxidative stress, impaired immune system, and wasting of skeletal muscle. Similarly, consuming too many incomplete proteins (protein that does not contain all 9 essential amino acids) can also lead to problems such as decreased cellular protein synthesis which is important for the functioning of a cell. (2)
When determining the quality of a protein, digestibility, bioavailability, and the amount of amino acids present are factors to consider. Bioavailability is the ability of a substance to be absorbed by the body so that it can receive nutrients. Digestibility is the breaking down of food so that it can be used as nutrients for the body. Plant protein is 70-90% digestible by the body and 60-70% bioavailable.
Plant-based protein
Some may consider plant protein to be low quality because many sources are missing essential amino acids such as lysine, tryptophan, methionine, and cysteine. But by mixing different protein sources together, you can ensure you are getting all the essential amino acids. For example, legumes contain a high amount of lysine but a very small amount of methionine. By combining legumes with cereal which contains a lot of methionine and cysteine, you allow for a meal with all the essential amino acids even if one food doesn’t necessarily contain all of it. An example of this combination could be rice and beans. The rice makes up for the lack of methionine in beans and the beans make up for the small amount of lysine in rice. Plant protein sources that contain all 9 essential amino acids include soybeans, quinoa, and chia seeds.
Below are some plant-based sources of protein with the estimated amount of protein it can provide (3) :
1 C edamame → 18g
1 C green peas → 8g
½ C beans → 6-9g
½ C cooked lentils → 12g
½ C grains → 5g
¼ C nuts → 9g
3.5 oz tofu → 8g
3 oz tempeh → 15-16g
1 oz seeds → 7-10g
1 TBSP nutritional yeast → 2g
Summary
You don’t have to consume meat in order to meet your protein goals. Plant protein can provide lots of great dietary fiber, vitamins, minerals, and bioactive compounds but in some cases doesn’t contain all 9 essential amino acids. Mixing different plant proteins can help with that issue but it’s important to choose quality protein sources to reap the benefits. If you can’t have a complete protein at every meal, focus on eating a variety of plant protein sources instead.
References
Ferrari, Luca, et al. “Animal- and Plant Based Protein Sources: A Scoping Review of Human Health Outcomes and Environmental Impact.” Shibboleth Authentication Request, 2022, www-ncbi-nlm-nih-gov.proxy2.library.illinois.edu/pmc/articles/PMC9741334/.
Iqbal, Sanaullah. “High Protein Foods: A Comparison of Animal Origin vs Plant Origin.” Springer Link, 2022, link-springer-com.proxy2.library.illinois.edu/chapter/10.1007/978-3-030-91206-2_1.
Pogored. “13 Of the Best Vegetarian and Vegan Protein Sources.” Cleveland Clinic, Cleveland Clinic, 29 Jan. 2021, health.clevelandclinic.org/13-of-the-best-vegetarian-and-vegan-protein-sources/.
