Nutrient glossary
What is isoleucine?
Isoleucine is a branched-chain essential amino acid that muscles burn directly and use for glucose regulation.
Reviewed 20 July 2026. General information, not medical advice.
The short version
Isoleucine is one of the three branched-chain amino acids (BCAAs) muscle tissue can burn as fuel without a trip through the liver. It also feeds into haemoglobin synthesis and helps muscle take up glucose.
Eggs, meat, fish, dairy, soy and lentils all deliver it; anyone hitting their protein target hits their isoleucine requirement automatically.
Daily reference
1.5 g a day
The adult requirement is about 20 mg per kg of body weight a day, covered by normal protein intake.
This is the fixed adult reference used across these pages. In the app, your amount adjusts to your body and way of eating.
Best food sources of isoleucine
| Food | Per serving | Per 100g |
|---|---|---|
| Chicken Breast | 2.37 g | 1.4 g |
| Roast Chicken | 2.14 g | 1.53 g |
| Sirloin Steak | 2.01 g | 1.34 g |
| Ribeye Steak | 2 g | 1.33 g |
| Duck Breast | 1.96 g | 1.4 g |
| Tuna Steak | 1.68 g | 1.29 g |
| Pork Chop | 1.65 g | 1.27 g |
| Halibut | 1.62 g | 1.16 g |
Common questions
- Do BCAA supplements beat food?
- No. Whole protein with all nine essentials builds muscle better than isolated BCAAs; supplements only patch a genuinely low-protein day.
- Which foods are rich in isoleucine?
- Eggs, chicken, tuna, Greek yogurt, soybeans and lentils are all dense sources relative to their protein.