Isoleucine
Also known as L-isoleucine, Ile
Isoleucine is an essential amino acid and one of the three branched-chain amino acids (BCAAs). The body cannot make it, so it must come from food, where it supports muscle repair and energy use during exercise.
Why it matters
What it does in your body
- Muscle protein synthesis and repair
- Branched-chain amino acid used for energy during exercise
- Glucose uptake and metabolism support
- Immune function support
Intake guidance
How much you need
The IOM sets the requirement at 19 mg/kg/day, about 1.3 g/day for a 70 kg adult. Any diet with enough total protein provides plenty.
What affects it
What affects your intake
Total protein intake
Adequate overall protein easily covers isoleucine, which is abundant in animal and plant proteins.
Exercise and training load
Endurance and resistance training raise BCAA turnover, though whole-food protein still meets the need.
Protein quality
Complete proteins such as meat, dairy, eggs, and soy supply isoleucine in ideal proportions.
In practice
Good to know
Deficiency is not a realistic risk on a normal diet. Isoleucine is often sold as part of BCAA supplements marketed to athletes, but for people already eating enough protein the extra provides little added benefit over a complete protein source like whey or food. Whole protein generally beats isolated BCAAs for building muscle.
Where to get it
Best food sources
The bottom line
A protein-adequate diet supplies all the isoleucine you need. Isolated BCAA supplements are rarely worth it if your total protein is on target.
Track isoleucine automatically
Isoleucine is one of the 92 nutrients Vora reads from a photo of your meal, so you can see where you stand without weighing or logging by hand.
Sources and method
The classification, roles, and guidance on this page come from the references below, drawing on the Institute of Medicine (now the National Academies) Dietary Reference Intakes and reputable nutrition science.
- Institute of Medicine (2005), Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids
This page is for general education, not medical advice. Reference intakes are population averages for healthy people and do not replace guidance from your doctor or a registered dietitian, especially if you are pregnant, managing a health condition, or considering supplements.