Amino acids
Amino acids are the building blocks of proteins. Some are essential because the body cannot make enough of them.
Essential amino acids
Essential amino acids must come from food. A complete protein provides all essential amino acids in useful proportions.
| Amino acid | Common role | Typical sources |
|---|---|---|
| Leucine | Muscle protein signalling and repair. | eggs, dairy, meat, fish, soy |
| Lysine | Tissue repair and protein synthesis. | meat, fish, dairy, legumes |
| Methionine | Methylation and sulphur amino acid metabolism. | eggs, fish, meat, grains |
| Tryptophan | Precursor for serotonin and niacin. | dairy, eggs, meat, seeds |
Complete protein
Eggs, meat, fish, dairy and soy usually have complete profiles. Some plant proteins can be lower in one limiting amino acid, so variety helps.
| Source | Practical comment |
|---|---|
| Egg | Complete essential amino acid profile. |
| Meat and fish | Complete and protein-dense. |
| Dairy | Casein and whey proteins. |
| Soy | Plant protein with a complete profile. |
| Legumes | Good in lysine, sometimes lower in methionine. |
| Grains | Can complement legumes. |
| Collagen | Useful structural protein, but not complete as the only source. |