Isoleucine
What it is and what it does
- Isoleucine is one of the nine essential amino acids, along with the others listed by MedlinePlus. (MedlinePlus Medical Encyclopedia (US National Library of Medicine): Amino acids (review date 1/21/2025))
- Isoleucine is one of the three branched-chain amino acids (BCAAs): valine, leucine and isoleucine. (Holecek M. Branched-chain amino acids in health and disease: metabolism, alterations in blood plasma, and as supplements. Nutr Metab (Lond) 2018;15:33. doi:10.1186/s12986-018-0271-1 (open access, CC BY))
- The branched-chain amino acids are used to build proteins or to produce energy, and also act as signals in metabolism. (Holecek M. Branched-chain amino acids in health and disease: metabolism, alterations in blood plasma, and as supplements. Nutr Metab (Lond) 2018;15:33. doi:10.1186/s12986-018-0271-1 (open access, CC BY))
- When isoleucine is broken down, its keto acid (ketoisoleucine) is turned into acetyl-CoA and succinyl-CoA, so it can feed both the glucose-making and the ketone-making pathways. (Holecek M. Branched-chain amino acids in health and disease: metabolism, alterations in blood plasma, and as supplements. Nutr Metab (Lond) 2018;15:33. doi:10.1186/s12986-018-0271-1 (open access, CC BY))
- The three branched-chain amino acids share a common breakdown (oxidation) pathway. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
- Most breakdown of the branched-chain amino acids starts in skeletal muscle, which has high activity of the first enzyme (BCAT) in the pathway. (Holecek M. Branched-chain amino acids in health and disease: metabolism, alterations in blood plasma, and as supplements. Nutr Metab (Lond) 2018;15:33. doi:10.1186/s12986-018-0271-1 (open access, CC BY))
Why it matters
- Studies show that too little of the branched-chain amino acids in the diet leads to poor growth and loss of body protein. (Holecek M. Branched-chain amino acids in health and disease: metabolism, alterations in blood plasma, and as supplements. Nutr Metab (Lond) 2018;15:33. doi:10.1186/s12986-018-0271-1 (open access, CC BY))
- In maple syrup urine disease, an inherited disorder, leucine, isoleucine and valine and their by-products build up in the body, and high levels are toxic to the brain. (MedlinePlus Genetics (US National Library of Medicine): Maple syrup urine disease (last updated July 1, 2017))
- ICMR-NIN notes that recent evidence suggests branched-chain amino acids (BCAAs) may increase the risk of certain non-communicable diseases. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- WHO/FAO/UNU note that the branched-chain amino acids (including isoleucine) may be toxic at high concentrations in the body; the body keeps their tissue levels very low. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)
General information, not medical advice — for your own needs, ask a doctor or dietitian.
How much is needed
| Who | Amount | What the figure is | Whose figure |
|---|---|---|---|
| Adults | 30 mg per g protein | Recommended amino acid pattern (ICMR-NIN 2020) | ICMR-NIN 2020 (as printed in DGI 2024 Table 8.2) |
| Adults (mean requirement) | 20 mg/kg body weight/day | Average requirement | FAO/WHO/UNU 2007 (not an Indian value) |
| Older children, adolescents and adults | 30 mg per g protein | Scoring pattern for protein quality | FAO 2013 (not an Indian value) |
India’s own figure (ICMR-NIN 2020) comes first. Figures from other bodies are shown only where they help, and say whose they are.
Sources: ICMR-NIN. Dietary Guidelines for Indians 2024; WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935; FAO (2013). Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92
In every millet and pseudo-cereal, per 100 g raw
| Grain | Amount | Source |
|---|---|---|
| Kodo millet | 4.55 g per 100 g protein | IFCT A017 |
| Little millet | 4.14 g per 100 g protein | IFCT A016 |
| Quinoa | 3.75 g per 100 g protein | IFCT A009 |
| Ragi (finger millet) | 3.7 g per 100 g protein | IFCT A010 |
| Bajra (pearl millet) | 3.45 g per 100 g protein | IFCT A003 |
| Jowar (sorghum) | 3.45 g per 100 g protein | IFCT A005 |
| Rajgira (amaranth) | 2.85 g per 100 g protein | IFCT A002 |
| Teff | 0.501 g | USDA FDC 169747 |
| Kuttu (buckwheat) | 0.498 g | USDA FDC 170286 |
| Proso millet | 0.465 g | USDA FDC 169702 |
Each grain has ONE source, named on its page: IFCT = Indian Food Composition Tables 2017 (ICMR-NIN) with its food code; USDA FDC; FAO WAFCT 2019; NIN 2007 via ICAR-IIMR. Values exactly as printed, not converted — tables differ in method, so compare within a source. Published values for the grain, not a laboratory test of our packs.
Absorption and food
- ICMR-NIN's model vegetarian diet ('My Plate for the Day') provides 41.2 mg isoleucine per g of protein, more than the 30 mg/g recommendation. (ICMR-NIN. Dietary Guidelines for Indians 2024)
- Compared with the requirement pattern, the branched-chain amino acids together (leucine, isoleucine, valine) are present at about 120-180% in milk, soya, potato, rice, maize and wheat proteins, and at 132% in the Indian diet. (WHO/FAO/UNU (2007). Protein and amino acid requirements in human nutrition: report of a joint FAO/WHO/UNU expert consultation. WHO Technical Report Series 935)