Isoleucine is one of the nine essential amino acids and, together with leucine and valine, is one of the branched-chain amino acids, also known as BCAAs. The body cannot make isoleucine itself and therefore depends on getting it through food. It is found in notable amounts in meat, fish, eggs, dairy products and in plant sources such as legumes and nuts.
Chemically speaking, isoleucine is involved in many metabolic processes, including energy metabolism and the building of muscle protein. Compared with leucine, isoleucine is studied on its own less often in research, but as part of the BCAA trio it plays a complementary role in amino acid metabolism.
Importance for nutrition and sport
For most people, a separate intake of isoleucine is not necessary, as a balanced, protein-rich diet with foods such as meat, fish, dairy products or legumes usually covers the requirement. In strength training, isoleucine is occasionally offered together with leucine and valine as a BCAA supplement, although the evidence on any additional benefit over an already sufficient protein intake is mixed.
If you already take in enough total protein over the day, you will usually cover your isoleucine requirement automatically. More on the branched-chain amino acids as a group and their possible role around training and recovery is explained in the BCAA guide.
