Article at a Glance:
- There is a wide misconception that plant proteins are incomplete because of their amino acid composition.
- Plant proteins contain all nine essential amino acids, but are often limiting in one or more.
- Getting enough amino acids from plants is not a problem as long as you eat enough calories and a variety of plant foods.
One of the most common questions about eating a plant-based diet is whether someone should be concerned about getting enough protein without animal products. Furthermore, many people wonder whether plant foods contain all of the essential amino acids.
The good news? You can absolutely meet your protein and amino acid needs on a well-planned plant-based diet. Unfortunately, the confusion around plant proteins persists despite these misconceptions being debunked long ago—and it has a lot to do with confusing semantics.
Let’s tackle these pervasive plant protein myths, how to ensure you’re getting enough protein on a plant-based diet, and how LiveComplete is changing the game—making plant-based nutrition even simpler.
Amino Acids 101
Protein is made up of amino acids. Think back to the brief nutrition unit in high school chem class, and the phrase “the building blocks of protein” probably rings a bell.
There are 20 amino acids in total, which fall into these categories:
- Essential amino acids: The 9 essential amino acids (EAAs) are the ones your body cannot make itself and, therefore, we have to get them through our diet.
- Non-essential amino acids: These are the remaining 11 amino acids, which your body can make by combining or altering the EAAs when you don’t get them from your diet. (For example, to make the amino acid cysteine, your body converts the EAA methionine into cysteine, which is used to produce glutathione, a key antioxidant that helps protect cells from damage. Pretty impressive.)
- Conditional amino acids: These are considered to be non-essential, except during certain seasons of life when your needs are higher—like pregnancy, adolescence, or when you’re healing from physical trauma or illness.
Let’s focus on the essential ones for now.
The essential amino acids and their primary functions include:
- Histidine: Important for growth, tissue repair, and the production of histamine.
- Isoleucine: Supports muscle metabolism, immune function, and hemoglobin production.
- Leucine: Plays a key role in protein synthesis, muscle repair, and blood sugar regulation.
- Lysine: Essential for collagen formation, calcium absorption, and immune function.
- Methionine: A precursor to sulfur-containing molecules important for metabolism and detoxification.
- Phenylalanine: A building block for neurotransmitters (brain chemical messengers) like dopamine and serotonin.
- Threonine: Supports the formation of collagen, elastin, and the immune system.
- Tryptophan: A precursor to serotonin, which influences mood, sleep, and appetite.
- Valine: A branched-chain amino acid (BCAA) that aids in muscle repair and energy production.
It’s important to get an abundance of all these EAAs because they play a role in nearly every biological function in your body.
Are Plant Proteins Incomplete?
You’ll find plenty of articles online stating that the “complete protein” label applies to animal products and only certain plant foods, such as tofu. Heck, you can even ask ChatGPT and it will tell you the same thing because it pulls its knowledge from the web, even if it’s not totally accurate.
Here’s the thing: All protein sources, both animal and plant, contain all 9 EAAs. In fact, the only food that completely lacks any amino acid is gelatin, which is missing tryptophan—so, hopefully, nobody out there is trying to survive on Jell-O. That also means that all plants have all 20 amino acids. Technically, no plant protein is “incomplete.”
The issue isn’t that plant proteins just don’t contain certain amino acids; it’s that certain types of plant foods commonly contain limiting (smaller) amounts of specific ones. (Except soy foods, which have an amino acid profile most similar to animal proteins).
Here are some examples:
- Legumes are limiting in methionine and cysteine
- Cereal grains are limiting in lysine and tryptophan
- Vegetables, nuts, and seeds are limiting in methionine, cysteine, lysine, and threonine
- Seaweed is limiting in histidine and lysine
Lysine tends to be the most limiting EAA overall on a plant-based diet, but you can get it by eating legumes, soy foods, seitan, quinoa, pumpkin seeds, and pistachios.
If you’re curious, you can take a closer look at the protein and amino acid content of selected plant foods in this table from VeganHealth.org (run by registered dietitians).
So, are plant proteins incomplete? Nope, but they sure are misunderstood.
Just search the web and you’ll find that a “complete protein” is frequently defined as a protein source that provides all 9 EAAs. In this case, all plant proteins are complete.
And while not every plant protein contains all of the 9 EAAs in sufficient amounts to meet the body’s needs if only that food were consumed, it is actually pretty easy to get enough EAAs by eating a wide variety of whole plant foods in your diet.
Variety is the spice of life, after all.
How Did the Myth Start?
Much like the whole “soy causes man boobs” myth (thank you, viral 2008 Men’s Health article), the “incomplete protein” myth stemmed from one false claim in a major publication that was shared over and over… and over again.
In 1971, the author and sociologist Frances Moore Lappe wrote in her well-meaning book Diet for a Small Planet that plant foods are deficient in some of the essential amino acids, therefore healthy vegetarians need to combine certain plant foods at the same time to make sure they get them all in the right amounts.
This was called protein complementing.
Do I Need to Combine Plant Proteins?
The idea of protein complementing (or complementary proteins) was that if certain plant proteins are low in some of the EAAs, you must combine different types to ensure you’re getting them all in each meal or snack.
Some popular suggestions include rice and beans, peanut butter and whole wheat toast, or tofu with sesame seeds.
Certainly, eating a wide variety of plant foods ensures your body gets enough EAAs from your diet, but is ensuring these pairings occur in the same meal really necessary? Nope. Eating plant proteins from all the categories (nuts, seeds, legumes, vegetables, and cereal grains) throughout the day ensures your body has enough to work with.
Feed it well, and it will take care of the rest.
In the 1981 tenth-anniversary edition of Lappe’s book, she retracted her statement, saying that while trying to end the myth that world hunger was inevitable, she accidentally created a new one: that we need to combine plant proteins for dietary adequacy.
Unfortunately, the myth lives on, despite the science showing otherwise (and plant-based nutrition experts everywhere pulling their hair out).
In a 2001 edition of the American Heart Association’s journal Circulation, the authors wrote: “Although plant proteins form a large part of the human diet, most are deficient in one or more essential amino acids and are therefore regarded as incomplete proteins.” This was refuted in a letter to the editor (and some back-and-forth with the original authors) by renowned plant-based medical doctor John McDougall.
Finally, on a page called Vegetarian Diets last updated in 2015, the American Heart Association states: “Whole grains, legumes, vegetables, seeds, and nuts all contain both essential and non-essential amino acids. You don’t need to consciously combine these foods (‘complementary proteins’) within a given meal.”
Still, when I search for research articles on the topic today, over two decades later, I find papers perpetuating this long-debunked myth.
It’s often done to paint animal proteins as being higher quality than plant proteins, even though plenty of studies show that diets high in animal proteins are associated with an increased risk for chronic diseases (e.g., cardiovascular disease, type 2 diabetes, and certain cancers) as well as shorter lifespan—but that’s an article for another time.
So, Can I Get Enough Protein on a Plant-Based Diet?
Okay, now that getting all the amino acids shouldn’t be causing you anxiety, back to protein in general.
Rest assured that you can meet your daily protein requirements whether you choose to eat animal products or not.
What’s more, a true protein deficiency is incredibly rare (even on a plant-based diet) as long as you’re getting enough calories—especially in developed countries like the United States, where we generally consume more than enough food overall.
Plus, there’s currently no scientific evidence that vegans and vegetarians are at a higher risk of protein deficiency, as long as they’re eating a calorie-sufficient diet that includes a variety of plant foods.
How much protein do you need? Well, there’s some nuance to that, depending on your age, sex, season of life (like pregnancy or advanced age), and activity level. In general, protein requirements are around 0.8–1.3 grams per kilogram of body weight per day.
There are plenty of plant foods that contain protein, some of which may surprise you.
Here’s how much protein you’ll get per serving of popular plant foods:
- 1 cup tempeh: 31 grams
- 3 oz seitan (vital wheat gluten): 21 grams
- 1 cup cooked firm tofu: 20 grams
- 1 cup cooked lentils: 18 grams
- 1 cup cooked chickpeas: 15 grams
- 3 Tbsp hemp seeds: 9 grams
- 1 cup cooked green peas: 8 grams
- 2 Tbsp nutritional yeast: 8 grams
- 1 cup cooked quinoa: 8 grams
- 2 Tbsp peanut butter: 8 grams
- 1 cup unsweetened soy milk: 7 grams
- ¼ cup almonds: 6 grams
- ½ cup dry oats: 5 grams
- ¼ cup sunflower seeds: 5 grams
- 1 cup cooked spinach: 5 grams
- 1 cup cooked broccoli: 5 grams
Overall, eating a variety of legumes (beans, peas, lentils), nuts and seeds, and soy foods (e.g., tofu, tempeh, edamame) is a great way to ensure adequate protein intake.
LiveComplete Takeaways
Here’s the bottom line: Plant proteins are technically complete and provide all 9 EAAs—but they’re also limiting and not always optimal.
While you don’t need to consciously combine proteins at every meal, it’s important to include a wide variety of whole and minimally processed plant foods in your diet if you don’t eat animal products.
And if you’re craving more efficiency from plant protein? Enter: LiveComplete.
Using our proprietary NutriMatch technology, we’ve paired EAAs to achieve near bioequivalence with human muscle, so you can get the building blocks you need from plant protein—while minimizing the extras.
Easy peasy. No compromises. Sacrifice nothing.
Plus, while most protein powders out there fall short, the amino acid profile in LiveComplete has over a 96% match to that of human muscle tissue (that’s better than meat!). Yep, you read that right—nearly identical and super efficient.
Join the LiveComplete family and no longer have to choose between doing what’s right and doing what’s right for you.
Sources
- Lopez MJ, Mohiuddin SS. (2024). Biochemistry, Essential Amino Acids. https://www.ncbi.nlm.nih.gov/books/NBK557845/
- Kudełka W, et al. (2021). Quality of Soybean Products in Terms of Essential Amino Acids Composition. https://pmc.ncbi.nlm.nih.gov/articles/PMC8398613/
- Lonnie M, et al. (2018). Protein for Life: Review of Optimal Protein Intake, Sustainable Dietary Sources and the Effect on Appetite in Ageing Adults. https://pmc.ncbi.nlm.nih.gov/articles/PMC5872778/
- VeganHealth.org. (2025). Protein and Amino Acid Content of Selected Plant Foods. https://veganhealth.org/protein/protein-part-2/#protein-foods
- St. Jeor S, et al. (2001). Dietary Protein and Weight Reduction: A Statement for Healthcare Professionals From the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. https://www.ahajournals.org/doi/10.1161/hc4001.096152?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
- McDougall J. (2002). Plant Foods Have a Complete Amino Acid Composition. https://doi.org/10.1161/01.CIR.0000018905.97677.1F
- McDougall J. (2002). Misinformation on Plant Proteins. https://doi.org/10.1161/01.CIR.0000042900.87320.D0
- American Heart Association. (2015). Vegetarian Diets. https://web.archive.org/web/20160203173445/http://www.heart.org/HEARTORG/HealthyLiving/HealthyEating/Vegetarian-Diets_UCM_306032_Article.jsp#.VrI6UXbP3wO
- Richter CK, et al. (2015). Plant protein and animal proteins: do they differentially affect cardiovascular disease risk? https://pmc.ncbi.nlm.nih.gov/articles/PMC4642426/
- Ardakani F, et al. (2024). Association between total, animal, and plant protein intake and type 2 diabetes risk in adults: A systematic review and dose-response meta-analysis of prospective cohort studies. https://doi.org/10.1016/j.clnu.2024.07.001
- Liao LM, et al. (2019). Substitution of dietary protein sources in relation to colorectal cancer risk in the NIH-AARP cohort study. https://pubmed.ncbi.nlm.nih.gov/31327110/
- Naghshi S, et al. (2020). Dietary intake of total, animal, and plant proteins and risk of all cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies. https://www.bmj.com/content/bmj/370/bmj.m2412.full.pdf
- Johansson G. (2018). Svårt att få brist på protein – för högt intag större risk – Lagom mängd mat – oavsett kosttyp – ger tillräckligt mycket [Protein deficiency – a rare nutrient deficiency]. https://pubmed.ncbi.nlm.nih.gov/29786804/
- Mariotti F, et al. (2019). Dietary Protein and Amino Acids in Vegetarian Diets-A Review. https://pmc.ncbi.nlm.nih.gov/articles/PMC6893534/
- VeganHealth.org. (2025). Assessing Protein Needs of a Population. https://veganhealth.org/protein/protein-part-2/#assessing-protein-need-of-a-population
