What is L-Isoleucine (L-Isoleucine)?
L-Isoleucine is one of the branched-chain amino acids (BCAAs) and is an essential amino acid; the body cannot produce it. In addition to being a building block of muscle protein, it plays a role in glucose uptake and energy metabolism. Within the BCAA trio, it is particularly associated with glucose utilization during exercise.
- CAS number: 73-32-5
- Molecular formula: C₆H₁₃NO₂
What is L-Isoleucine Used For? Why is it Used?
Isoleucine is necessary for a balanced BCAA profile and complete essential amino acid balance. In sports and clinical nutrition, it is a complementary component of the mixture that supports muscle protein synthesis and recovery when used together with leucine and valine.
Usage as Sports Nutrition
The following information is based on sports nutrition research (ISSN position stands, randomized controlled trials, and meta-analyses); the level of evidence is clearly stated for each item.
- Part of BCAA: Isoleucine is an integral component of the BCAA trio that supports muscle protein synthesis; it is part of the balanced ratio in the anabolic response triggered by leucine.
- Glucose metabolism: Isoleucine can stimulate glucose uptake and utilization in skeletal muscle; this has attracted interest in the context of energy supply during exercise.
- Recovery support: In studies reducing exercise-induced muscle damage, isoleucine contributes to alleviating muscle soreness (DOMS) as part of a BCAA mixture.
- Dosage/timing: It is generally taken as a BCAA mixture before/during/after training; evidence for the performance effect of isoleucine alone is limited.
Forms and Differences
L-Isoleucine is offered in different forms; form selection is made based on bioavailability, stability, and intended use:
- Fermentation-derived L-Isoleucine: The natural L-form produced by microbial fermentation; white crystalline powder. It is a component of BCAA mixtures and free amino acid products.
- BCAA mixture component: Rarely used alone, it is generally used together with leucine and valine in 2:1:1 or 4:1:1 BCAA ratios.
Usage in Dietary Supplements
- Typical dosage: Generally taken not alone but within a BCAA mixture (the amount allocated to it within 5-10 g total BCAAs). Free isoleucine can also be added to complete the protein profile.
- Essentiality: It must be obtained through diet; meat, fish, eggs, dairy products, and legumes are the main sources.
- Energy metabolism: Isoleucine is both glucogenic and ketogenic and is associated with glucose uptake in muscle cells.
Usage in the Food Industry
- Protein enrichment: Used to provide a balanced BCAA profile in sports and clinical nutrition products.
- Clinical/enteral nutrition: Included to complete the balance of essential amino acids in medical nutrition solutions.
Effects on Health
- Role as essential amino acid: Necessary for normal protein synthesis and maintenance of muscle tissue.
- Energy and glucose balance: Its contribution to glucose uptake is an established physiological characteristic; however, there is no EFSA approval for clinical/performance claims regarding this.
Status of Health Claims (EFSA) — Transparent Information
EFSA has not authorized claims for BCAAs, including isoleucine, regarding muscle mass and recovery (EFSA Journal 2010;8(10):1790). There is no specific approved health claim for isoleucine; scientific usage is based on physiological roles and BCAA RCTs.
Usage Limits and Safety
- Typical usage dose: Within a BCAA mixture; total BCAA 5-10 g/day is typical. No standard dose has been specified for isoleucine alone.
- Upper intake level (UL): There is NO established numerical upper safe intake limit (UL) (EFSA/NIH).
- Turkish legislation (Sports Foods / TETGK): Amino acid supplementation is permitted under the Turkish Dietary Supplements Regulation; a specific numerical limit for isoleucine could not be confirmed in this research — official regulation annexes should be verified.
Excessive and unbalanced use of a single amino acid can disrupt the absorption of other BCAAs; a balanced mixture is recommended.
Technical Specifications
| Parameter | Value |
|---|---|
| Moisture | ≤5.0 % |
| Total Heavy Metals | ≤10 ppm |
| E. Coli | Negative in 10 g |
| Salmonella | Negative in 25 g |
| Solubility | Water Soluble |
Scientific Studies
The following independent studies relate to the component's effects on sports performance, bioavailability, and efficacy (study types are specified):
- PubMed 16365096 — Branched-chain amino acids activate key enzymes of protein synthesis after physical exercise
- PubMed 34669012 — Use of BCAAs in reducing delayed onset muscle soreness after a single exercise session: systematic review and meta-analysis
Technical Documents and Supply — Asuka Kimya
You can contact Asuka Kimya for SDS, TDS, CoA, and supply conditions for L-Isoleucine.
References
The usage, sports nutrition, and health information on this page have been compiled from official legislation/institution sources (EFSA, NIH ODS, ISSN, Turkish Food Codex Sports Foods / Dietary Supplements Regulation) and independent scientific publications (PubMed). The product is a food supplement/sports nutrition raw material; it does not intend to diagnose or treat diseases.