The nine essential amino acids your body can't make, what each one does, how much you need and which foods provide them.
Essential amino acids are the nine amino acids your body cannot make, so they must come from food: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. They are part of every protein in your body, from muscle to enzymes and hormones. A varied diet with enough protein covers all nine.
This guide explains what amino acids are, what each essential amino acid does, how much you need, and which foods provide them, including plant-based ones.
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Shop WAM Protein →What are amino acids?
Amino acids are the building blocks of protein. The human body uses 20 different amino acids, which link together in long chains to form proteins. Each amino acid has the same basic structure: an amino group, a carboxyl group and a unique side chain. The side chain gives each amino acid its properties and decides how the finished protein folds. The order of amino acids in a chain determines whether the protein becomes muscle fibre, an enzyme, an antibody or a hormone. Besides building proteins, amino acids are raw materials for neurotransmitters, energy production and many metabolic processes (Wu, 2009).
What is the difference between essential, non-essential and conditionally essential amino acids?
Essential amino acids must come from food, while non-essential amino acids can be made by the body. Nine of the 20 amino acids are essential: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. The other eleven are non-essential, because the body builds them from other molecules. Some non-essential amino acids become conditionally essential during illness, injury or intense stress, when the body cannot make enough of them. Arginine, cysteine, glutamine, glycine, proline and tyrosine belong to this group, with arginine and glutamine the best-studied examples (Morris et al., 2017). "Non-essential" therefore does not mean unimportant. It only means that the body can usually produce enough itself.
What do the nine essential amino acids do?
Each essential amino acid has its own jobs in the body, beyond building protein. The three branched-chain amino acids (BCAAs) leucine, isoleucine and valine are especially important for muscle. Leucine is the strongest single trigger for muscle protein synthesis, which is why it gets so much attention in sports nutrition. Read more in our guide to leucine and our article on BCAAs. The table gives an overview of each essential amino acid and good food sources.
| Amino acid | Key functions | Good food sources |
|---|---|---|
| Histidine | Precursor of histamine; tissue growth and repair; part of haemoglobin | Soy, legumes, meat, fish |
| Isoleucine (BCAA) | Muscle metabolism; energy supply in muscle | Soy, lentils, eggs, dairy |
| Leucine (BCAA) | Strongest signal for muscle protein synthesis | Soy, whey, peanuts, lentils |
| Lysine | Protein building, collagen formation, calcium absorption | Legumes, tofu, quinoa, dairy |
| Methionine | Starts every new protein; sulphur source for cysteine | Rice, oats, sesame, Brazil nuts, eggs, fish |
| Phenylalanine | Precursor of tyrosine, dopamine and noradrenaline | Soy, peanuts, dairy, eggs |
| Threonine | Collagen, elastin and protective gut mucus | Lentils, tofu, dairy |
| Tryptophan | Precursor of serotonin and melatonin | Oats, soy, pumpkin seeds, dairy |
| Valine (BCAA) | Muscle metabolism and energy | Soy, peanuts, dairy |
Two of these amino acids also affect your brain chemistry. Tryptophan is the starting material for serotonin, a neurotransmitter involved in mood and sleep (Jenkins et al., 2016). Phenylalanine is converted into tyrosine, which the body uses to produce dopamine and noradrenaline (Fernstrom & Fernstrom, 2007).
How much of each essential amino acid do you need?
Adults need between 4 and 39 mg of each essential amino acid per kilogram of body weight per day, depending on the amino acid. The World Health Organization (WHO) set these values as minimum requirements for healthy adults (WHO/FAO/UNU, 2007). Leucine has the highest requirement and tryptophan the lowest. If you eat enough total protein from varied sources, you cover these amounts automatically. Active people who eat 1.4–2.0 g of protein per kg body weight usually take in several times the minimum.
| Amino acid | mg per kg body weight per day | Example for 65 kg |
|---|---|---|
| Histidine | 10 | 0.65 g |
| Isoleucine | 20 | 1.3 g |
| Leucine | 39 | 2.5 g |
| Lysine | 30 | 2.0 g |
| Methionine + cysteine | 15 | 1.0 g |
| Phenylalanine + tyrosine | 25 | 1.6 g |
| Threonine | 15 | 1.0 g |
| Tryptophan | 4 | 0.26 g |
| Valine | 26 | 1.7 g |
Minimum requirements for healthy adults according to WHO/FAO/UNU (2007).
"Your body can't store essential amino acids the way it stores fat or carbohydrates, so it needs a steady supply from food every day."
– Dr. Anna Falk, PhD chemist and founder of WAM
What is a complete protein?
A complete protein contains all nine essential amino acids in amounts that match human needs. Most animal proteins, such as eggs, dairy, meat and fish, are complete. Among plant foods, soy and quinoa are complete proteins. Many other plant proteins are low in one essential amino acid, called the limiting amino acid. Grains such as rice and wheat are low in lysine, while legumes such as peas and lentils are low in methionine. Because their gaps are opposite, grains and legumes complement each other well. This is also why pea and rice protein are often blended in protein powders. Our guide to the best vegan protein sources compares soy, pea, rice and hemp in detail.
Can you get all essential amino acids on a vegan diet?
Yes, a varied vegan diet with enough protein provides all nine essential amino acids. You do not need to combine complementary proteins in the same meal, because your body draws on amino acids from everything you eat over the day (Mariotti & Gardner, 2019). Practical combinations are beans with rice, hummus with wholegrain bread, or lentil curry with quinoa. Soy foods such as tofu and tempeh are complete on their own. A well-designed plant protein blend can also match animal protein: in a controlled study, a blend of wheat, corn and pea protein stimulated muscle protein synthesis as much as the same amount of milk protein (Pinckaers et al., 2023). For more ideas, see our list of high-protein foods.
Do you need EAA or BCAA supplements?
Most people do not need separate EAA or BCAA supplements if they eat enough complete protein. Whole protein from food or protein powder already contains all essential amino acids in a balanced ratio. Isolated BCAAs supply only three of the nine essential amino acids, so they cannot support muscle protein synthesis as fully as complete protein can (Church et al., 2020). EAA supplements can be useful in specific situations, for example when appetite or protein intake is low. Our comparison of protein powder, BCAAs and EAAs explains when each makes sense.
Frequently asked questions about essential amino acids
How many essential amino acids are there?
There are nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Your body cannot produce them, so they have to come from food. The remaining eleven of the 20 protein-building amino acids are non-essential, although some become conditionally essential during illness or stress.
Which essential amino acid is most important for muscle building?
Leucine is the most important single amino acid for muscle building. It directly activates the mTOR pathway, which switches on muscle protein synthesis. Leucine alone is not enough, however. Your muscles need all nine essential amino acids as building material, which is why complete protein works better than leucine or BCAAs on their own.
Can you be deficient in essential amino acids?
A deficiency is rare in people who eat enough protein from varied sources. It can occur with very low protein intakes, restrictive diets, some illnesses or reduced appetite in older age. Typical signs of low protein intake include loss of muscle mass, slow wound healing and frequent infections. If you suspect a deficiency, talk to a doctor or dietitian.
Do plant proteins have to be combined in the same meal?
No, plant proteins do not need to be combined in the same meal. Your body pools amino acids from all the meals you eat during the day. Eating grains and legumes at different times still gives you a complete amino acid profile. What matters is a varied diet and enough total protein.
Which foods contain all nine essential amino acids?
Soy foods such as tofu, tempeh and edamame, quinoa, eggs, dairy products, meat and fish contain all nine essential amino acids in good proportions. Protein powders based on whey or on plant blends such as soy, pea and rice are also complete. Most other plant foods are low in one essential amino acid but complete each other when combined.
About WAM Protein
WAM Protein is a vegan protein powder made from soy, pea and rice protein, which together provide all nine essential amino acids. Added free-form leucine brings each 30 g serving to 2.5 g of leucine and 21–23 g of protein, lightly sweetened with stevia only. Try all four flavours with the Sample Pack.
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- Wu G. Amino acids: metabolism, functions, and nutrition. Amino Acids. 2009;37(1):1-17. PubMed
- Morris CR, et al. Acquired Amino Acid Deficiencies: A Focus on Arginine and Glutamine. Nutr Clin Pract. 2017;32(1_suppl):30S-47S. PubMed
- Jenkins TA, et al. Influence of Tryptophan and Serotonin on Mood and Cognition with a Possible Role of the Gut-Brain Axis. Nutrients. 2016;8(1):56. PubMed
- Fernstrom JD, Fernstrom MH. Tyrosine, phenylalanine, and catecholamine synthesis and function in the brain. J Nutr. 2007;137(6 Suppl 1):1539S-1547S. PubMed
- WHO/FAO/UNU Expert Consultation. Protein and amino acid requirements in human nutrition. WHO Technical Report Series 935. 2007. WHO
- Mariotti F, Gardner CD. Dietary Protein and Amino Acids in Vegetarian Diets – A Review. Nutrients. 2019;11(11):2661. PubMed
- Pinckaers PJM, et al. The Muscle Protein Synthetic Response to the Ingestion of a Plant-Derived Protein Blend Does Not Differ from an Equivalent Amount of Milk Protein in Healthy Young Males. J Nutr. 2023;152(12):2734-2743. PubMed
- Church DD, et al. Essential Amino Acids and Protein Synthesis: Insights into Maximizing the Muscle and Whole-Body Response to Feeding. Nutrients. 2020;12(12):3717. PubMed
