Short answer
The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Your body cannot make them, so they must come from food or supplements. Leucine, isoleucine and valine are also called the branched-chain amino acids (BCAAs).
The nine, one by one
The nine essential amino acids
| Amino acid | Code | Note |
|---|---|---|
| Leucine | Leu, L | A BCAA, studied as a trigger for muscle protein synthesis |
| Isoleucine | Ile, I | A BCAA |
| Valine | Val, V | A BCAA |
| Lysine | Lys, K | Often lower in plant proteins |
| Methionine | Met, M | Contains sulfur; often lower in plant proteins |
| Phenylalanine | Phe, F | Has a ring side chain |
| Threonine | Thr, T | |
| Tryptophan | Trp, W | Usually the smallest amount on a label |
| Histidine | His, H | Listed as essential for adults |
The list and the essential, non-essential and conditionally essential groups come from MedlinePlus, the U.S. National Library of Medicine's health site. Requirements for each amino acid by body weight are set out by the WHO, FAO and UNU expert report.
Essential, non-essential, conditionally essential
- Essential (9): must come from food.
- Non-essential (11): alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine and tyrosine. Your body makes them.
- Conditionally essential: usually made by the body but needed from food during illness or stress (MedlinePlus).
Why EAAs get so much attention
In studies of muscle, the essential amino acids appear to do the heavy lifting. In older adults, 18 g of EAAs increased muscle protein balance as much as 40 g of mixed amino acids that included 22 g of non-essential ones (Volpi 2003). Earlier work in younger volunteers reached a similar conclusion (Tipton 1999). The ISSN position stand says it is the EAAs that are required to stimulate muscle protein synthesis (ISSN 2017).
Where to get them from food
Proteins differ in how much of their protein is essential. In one analysis, EAAs made up 43% of whey protein, 39% of milk protein and 32% of egg protein, against 21 to 22% for oat, lupin and wheat protein isolates (Gorissen 2018). Plant proteins also tended to run lower in methionine and lysine.
For most people eating varied meals with enough protein, food covers all nine. Supplements are an option, not a requirement. See EAA vs whey and EAAs for vegans.
Questions people ask
What is a mnemonic for the 9 essential amino acids?
A common one is "PVT TIM HLL": phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, histidine, leucine, lysine. A longer school version, "PVT TIM HALL", adds arginine, which is conditionally essential and not one of the nine for adults.
Why are they called essential?
Because the body cannot make them in adequate amounts, so they are essential in the diet. Non-essential amino acids are still needed; your body can simply make them.
Which foods have all nine essential amino acids?
Animal proteins such as eggs, dairy, meat and fish contain all nine in good proportions. Soy and quinoa are also complete. Most other plant foods contain all nine but are low in one or more, which is why variety across the day matters.
Do I need to combine proteins at every meal?
No. MedlinePlus notes that you do not need to eat essential and non-essential amino acids at every meal; what matters is a balance across the whole day.
What are conditionally essential amino acids?
Amino acids that are usually not essential but can become so during illness or stress, such as arginine, cysteine, glutamine, tyrosine, glycine, proline and serine.
Sources
- MedlinePlus (U.S. National Library of Medicine), Amino acids
- WHO/FAO/UNU, Protein and amino acid requirements in human nutrition, WHO Technical Report Series 935 (2007)
- Volpi et al., Essential amino acids are primarily responsible for the amino acid stimulation of muscle protein anabolism in healthy elderly adults, Am J Clin Nutr (2003)
- Tipton et al., Nonessential amino acids are not necessary to stimulate net muscle protein synthesis in healthy volunteers, J Nutr Biochem (1999)
- Jäger et al., International Society of Sports Nutrition position stand: protein and exercise, J Int Soc Sports Nutr (2017)
- Gorissen et al., Protein content and amino acid composition of commercially available plant-based protein isolates, Amino Acids (2018)
Last reviewed October 12, 2026. Formulas, labels and listings change; check the current label before you buy. This page is general information, not medical advice.