L-isoleucine is an essential amino acid. Unable to be produced by the body, isoleucine must be sourced from diet. This amino acid has many roles within the human body. It is best known for its ability to support blood clotting at wound sites and assisting with muscle tissue repair. L-isoleucine can also help to boost energy levels and improve stamina.
Consequently, this is a widely used amino acid supplement for body builders and endurance-based athletes1. Not only does it provide an added energy boost, it also helps the body to repair faster following periods of strenuous physical activity2.
A branched-chain amino acid
L-isoleucine is one of three specialised amino acids known as branched-chain amino acids (BCAAs). This group also includes l-leucine and l-valine. Branched-chain amino acids assist with muscle recovery following exercise. L-isoleucine is broken down within the muscle tissue to generate energy. Additionally, this amino acid helps to regulate blood sugar levels to stabilise energy levels. Isoleucine significantly increases the body’s ability to utilise glucose during exercise. However, it does not promote the synthesis of glycogen.
Symptoms of a l-isoleucine deficiency
People with low levels of this essential amino acid will experience symptoms similar to hypoglycaemia. This can include dizziness, fatigue, headaches, confusion, irritability, and depression. People with a balanced diet rarely have a deficiency in this amino acid.
Natural sources of l-isoleucine
High protein foods are typically rich in this essential amino acid. Meat, fish, eggs, nuts, seeds, and pulses are all good sources of isoleucine. For people with low-protein diets or individuals that exercise a lot it is recommended to consider supplementation. This amino acid is regularly found in dietary supplements.
However, it’s important not to take l-isoleucine alone and it should always be paired with l-valine and l-leucine for the best results. The recommended dosage ratio is 1 milligram of l-isoleucine together with 2 milligrams of both l-valine and l-leucine. This is thought to provide optimal absorption. There are many supplements that contain all BCAAs at the correct ratios for convenience.
Prior to taking any supplement it is important to first consult with a medical practitioner. For people with impaired kidney or liver function isoleucine may worsen these conditions.
- “Bajotto, G. et al. (2011). Effect of BCAA Supplementation During Unloading on Regulatory Components of Protein Synthesis in Atrophied Soleus Muscles. European Journal of Applied Physiology. Volume 111, Issue 8, (pp. 1815-28).” ↩
- “Sharp, C. and Pearson, D. (2010). Amino Acid Supplements and Recovery from High-Intensity Resistance Training. Journal of Strength and Conditioning Research. Volume 24, Issue 4, (pp. 1125-30).” ↩