Essential vs Non-Essential Amino Acids
A complete guide to the 20 standard amino acids, their dietary classification, and the mnemonic that makes them unforgettable.
What Are Essential and Non-Essential Amino Acids?
The human body requires 20 standard amino acids to build proteins. These are classified based on whether the body can synthesize them internally.
- Essential amino acids cannot be synthesized by the body at all, or cannot be synthesized in sufficient quantities. They must be obtained from the diet.
- Non-essential amino acids can be produced endogenously from metabolic intermediates, so they do not need to come from food.
- Conditionally essential amino acids become essential under certain physiological conditions such as illness, stress, or rapid growth.
The PVT TIM HALL Mnemonic
The easiest way to remember the nine essential amino acids is:
“PVT TIM HALL”
| Letter | Amino Acid |
|---|---|
| P | Phenylalanine |
| V | Valine |
| T | Threonine |
| T | Tryptophan |
| I | Isoleucine |
| M | Methionine |
| H | Histidine |
| A | Arginine* |
| L | Leucine |
| L | Lysine |
*Arginine is conditionally essential (essential in childhood and during recovery from trauma).
Complete Amino Acid Table
| Amino Acid | Classification | Dietary Sources |
|---|---|---|
| Alanine | Non-essential | Poultry, dairy, corn |
| Arginine | Conditional | Nuts, seeds, soy, meat |
| Asparagine | Non-essential | Poultry, eggs, dairy |
| Aspartate | Non-essential | Meat, dairy, legumes |
| Cysteine | Conditional | Poultry, yogurt, garlic |
| Glutamate | Non-essential | Tomatoes, parmesan, soy sauce |
| Glutamine | Conditional | Beef, chicken, fish, eggs |
| Glycine | Conditional | Bone broth, meat, gelatin |
| Histidine | Essential | Meat, fish, soy, legumes |
| Isoleucine | Essential | Eggs, soy protein, seaweed |
| Leucine | Essential | Meat, fish, dairy, soy |
| Lysine | Essential | Red meat, legumes, dairy |
| Methionine | Essential | Fish, meat, eggs, sesame seeds |
| Phenylalanine | Essential | Meat, fish, dairy, nuts |
| Proline | Conditional | Meat, dairy, collagen |
| Serine | Conditional | Soy, nuts, meat, dairy |
| Threonine | Essential | Cottage cheese, wheat germ |
| Tryptophan | Essential | Turkey, cheese, nuts |
| Tyrosine | Conditional | Meat, fish, dairy, almonds |
| Valine | Essential | Soy, mushrooms, grains |
Dietary Sources for Each Essential Amino Acid
For those tracking intake, here are the best single food sources for each essential amino acid:
- Phenylalanine: Soybeans, beef, chicken, eggs
- Valine: Soy, mushrooms, sesame seeds
- Threonine: Cottage cheese, wheat germ, gelatin
- Tryptophan: Turkey, milk, tuna, cheddar cheese
- Isoleucine: Seaweed, soy, eggs, liver
- Methionine: Fish, meat, eggs, sesame seeds
- Histidine: Tuna, salmon, pork, chicken
- Leucine: Chicken, beef, fish, soybeans
- Lysine: Red meat, beans, Parmesan cheese
Why This Matters
A complete protein contains all nine essential amino acids in adequate proportions. Animal-based foods (meat, fish, eggs, dairy) are complete proteins. Most plant-based foods are incomplete — they lack one or more essential amino acids — but combining complementary sources (for example, rice and beans) can provide a complete profile.
Mnemonic
“PVT TIM HALL” — imagine a soldier (Private Tim Hall) guarding the supply of essential amino acids. The soldier must be present (essential) because he cannot make the supplies himself.