Quick answer
Amino acids are the building blocks of protein. Nine are essential, meaning you must get them from food. The rest are non-essential, meaning your body can make them. Some popular supplement ingredients, such as taurine, L-theanine and L-citrulline, aren't used to build proteins at all.
Essential
9 amino acids you must get from food
Non-essential
Your body can make them
Example essential
L-lysine
Example non-essential
L-tyrosine
The nine essential amino acids
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine
Eggs, meat, fish, dairy, soy and quinoa contain all nine. Other plant foods can be combined across the day to provide them.
Where popular supplements fit
| Ingredient | Type | Used in proteins? | Food sources |
|---|---|---|---|
| L-lysine | Essential amino acid | Yes | Meat, dairy, legumes |
| L-tyrosine | Non-essential (made from phenylalanine) | Yes | Cheese, meat, soy |
| Taurine | Amino sulfonic acid | No | Meat, fish, seafood |
| L-theanine | Non-protein amino acid | No | Tea leaves |
| L-citrulline | Non-protein amino acid | No | Watermelon |
| NAC | Form of cysteine | Cysteine is | Cysteine: eggs, meat, legumes |
What does "conditionally essential" mean?
Some non-essential amino acids, such as tyrosine and cysteine, are sometimes called conditionally essential. The body normally makes them, but production depends on having enough of other amino acids (for example, tyrosine is made from phenylalanine).
Reading amino acid labels
Tip: Look for the "L-" prefix. L-forms are the forms found in food and in the body.
Frequently asked questions
How many amino acids are there?
Twenty amino acids are commonly used to build human proteins. Nine of these are essential.
Is tyrosine essential?
No. Tyrosine is non-essential because the body makes it from phenylalanine, an essential amino acid.
Is taurine an amino acid?
Taurine is often called an amino acid, but technically it's an amino sulfonic acid and isn't used to build proteins.
Keep reading
This article is general information only and is not medical advice. Always read the label and follow the directions for use. Dietary supplements should not replace a balanced diet. If you are pregnant, breastfeeding, taking medication or have a medical condition, speak with your doctor or pharmacist before taking a new supplement.
