Table of ContentsView AllTable of ContentsBenefits of IsoleucineBlood SugarMuscle Damage and SorenessExercise FatigueBlood Flow in the BrainImmune SystemDosageSafetySimilar Supplements

Table of ContentsView All

View All

Table of Contents

Benefits of Isoleucine

Blood Sugar

Muscle Damage and Soreness

Exercise Fatigue

Blood Flow in the Brain

Immune System

Dosage

Safety

Similar Supplements

Isoleucine is one of the three branched-chain amino acids (BCAAs). It is considered an essential amino acid because the body cannot produce it, and it must be obtained through diet or supplementation.

Isoleucine has been studied to treat post-exercise muscle soreness.Branched-chain amino acids have also been studied to reduce postexercise muscle damage and maintain or improve muscle function.

Not only does isoleucine serve as a building block for proteins, but it also serves as a signaling molecule that regulates the following:

1. Blood Sugar

Further studies looking at the effect of isoleucine in people withtype 2 diabetesare needed to determine how it may affect people with this condition.

On the contrary, high dietary intake of BCAAs has been associated with an increased risk of type 2 diabetes.However, it is unclear if an increased level of BCAAs causes type 2 diabetes.

2. Muscle Damage and Soreness

An analysis of a collection of studies found that BCAAs reduced muscle damage biomarkers (measurable indicators) and muscle soreness following muscle-damaging exercises.

Because BCAAs were examined collectively, it is unclear if isoleucine alone affects muscle damage and soreness.

3. Exercise Fatigue

A study to determine the effect of BCAA supplementation on fatigue and muscle damage biomarkers (indicators) was conducted in 26 male subjects who used a type of exercise equipment called a bicycle ergometer. The study found that BCAAs decreasedserotoninconcentration (a chemical messenger contributing to fatigue) during endurance exercise.

The decreased serotonin concentration then reduced the concentration of muscle damage markers (e.g.,creatinine kinaseandlactate dehydrogenase) and enhanced exercise performance.

Since the study used a combination of three BCAAs, the effect of isoleucine alone on fatigue and muscle damage biomarkers remains unclear.

Further studies with larger sample sizes solely looking at isoleucine are needed to clarify the results.

4. Blood Flow in the Brain

In a study of 27 people withcirrhosis(scarring of the liver) andhepatic encephalopathy(toxin buildup in the brain due to liver disease), supplementation with isoleucine for one year improved blood flow in the brain.

Despite the positive finding, larger sample sizes are needed to confirm the results.

5. Immune System

Results from a review of a group of studies showed that BCAA intake in people with cancer undergoing surgery decreased the risk ofpostoperative(after surgery) infections as well as the risk ofascites(fluid buildup in the abdomen) compared to the control group.

Since the majority of the clinical studies looked at individuals with liver cancer, it is unclear if the results applied to individuals with other types of cancer.

Isoleucine Supplement Facts

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.

The following dosages were used in clinical trials:

Blood sugar:Two hundred milliliters (mL) of intragastric infusion consisting of 10 g of crystalline isoleucine and 58 milligrams (mg) of calcium chloride and water were given via a feeding tube that goes through the nose and into the stomach.

Muscle damage and soreness:Studies examining the effect of BCAA supplementation on muscle damage and soreness used a BCAA ratio of 2-to-1-to1 (leucine-to-isoleucine-to-valine). The dosage of BCAAs was between 0.20 and 1.76 grams per kilogram (g/kg) of body weight and between 12 and 260 g. The duration of BCAA supplementation ranged from one to 28 days.

Supplementing with BCAAs for at least seven days before muscle-damaging exercise may effectively limit exercise-induced muscle damage from exercise.

Side Effects

Branched-chain amino acids given through the veins were associated with increased blood sugar levels and urine production post-surgery.

Although no side effects were reported in some studies, other studies have reported the following side effects of BCAAs:

While these side effects are associated with BCAAs, it is unclear if isoleucine alone would have such side effects.

Interactions

The following interactions should be noted when taking isoleucine:

It is essential to carefully read a supplement’s ingredients list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Review this supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.

Precautions

The following precautions should be noted when taking isoleucine:

Like isoleucine,leucineandvalineare also BCAAs.

How isoleucine and leucine work to lower blood sugar levels also differs. Whereas isoleucine lowered blood sugar levels without affecting insulin levels, leucine increased insulin levels.

Isoleucine vs. Leucine

However, preliminary data suggest that isoleucine and valine alongside leucine enhances protein synthesis to a greater extent than leucine alone.

Yet, ingesting BCAAs and other essential amino acids (i.e., amino acids that the body cannot produce) remains necessary for maximal muscle protein synthesis following resistance exercise training.

Summary

Isoleucine is a BCAA crucial in protein synthesis and blood sugar regulation.

Some studies suggest a potential use for isoleucine and BCAAs in lowering blood sugar levels, reducing muscle damage and soreness, improving exercise fatigue, improving hepatic encephalopathy, and decreasing the risk of infections post-surgery.

Before starting isoleucine supplements, be sure to consult with your healthcare provider to determine if it is appropriate for you.

22 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Ramzan I, Ardavani A, Vanweert F, et al.The association between circulating branched chain amino acids and the temporal risk of developing type 2 diabetes mellitus: A systematic review & meta-analysis.Nutrients. 2022;14(20):4411. doi:10.3390/nu14204411

Doma K, Singh U, Boullosa D, Connor JD.The effect of branched-chain amino acid on muscle damage markers and performance following strenuous exercise: a systematic review and meta-analysis.Appl Physiol Nutr Metab. 2021;46(11):1303-1313. doi:10.1139/apnm-2021-0110

Arroyo-Cerezo A, Cerrillo I, Ortega Á, et al.Intake of branched chain amino acids favors post-exercise muscle recovery and may improve muscle function: optimal dosage regimens and consumption conditions.J Sports Med Phys Fitness. 2021;61(11):1478-1489. doi:10.23736/S0022-4707.21.11843-2

Nie C, He T, Zhang W, et al.Branched chain amino acids: beyond nutrition metabolism.Int J Mol Sci. 2018;19(4):954. doi:10.3390/ijms19040954

Sloun BV, Goossens GH, Erdos B, et al.The impact of amino acids on postprandial glucose and insulin kinetics in humans: A quantitative overview.Nutrients. 2020;12(10):3211. doi:10.3390/nu12103211

Zheng Y, Li Y, Qi Q, et al.Cumulative consumption of branched-chain amino acids and incidence of type 2 diabetes.Int J Epidemiol. 2016;45(5):1482-1492. doi:10.1093/ije/dyw143

Kim DH, Kim SH, Jeong WS, et al.Effect of BCAA intake during endurance exercises on fatigue substances, muscle damage substances, and energy metabolism substances.J Exerc Nutrition Biochem. 2013;17(4):169-180. doi:10.5717/jenb.2013.17.4.169

Romeiro FG, Ietsugu MDV, Franzoni LC, et al.Which of the branched-chain amino acids increases cerebral blood flow in hepatic encephalopathy? A double-blind randomized trial[published correction appears in Neuroimage Clin. 2020;28:102497].Neuroimage Clin. 2018;19:302-310. doi:10.1016/j.nicl.2018.03.028

Cogo E, Elsayed M, Liang V, et al.Are supplemental branched-chain amino acids beneficial during the oncological peri-operative period: a systematic review and meta-analysis.Integr Cancer Ther. 2021;20:1534735421997551. doi:10.1177/1534735421997551

PubChem.I-Isoleucine.

Holeček 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

Lo EKK, Felicianna, Xu JH, et al.The emerging role of branched-chain amino acids in liver diseases.Biomedicines. 2022;10(6):1444. doi:10.3390/biomedicines10061444

Khemtong C, Kuo CH, Chen CY, Jaime SJ, Condello G.Does branched-chain amino acids (BCAAs) supplementation attenuate muscle damage markers and soreness after resistance exercise in trained males? A meta-analysis of randomized controlled trials.Nutrients. 2021;13(6):1880. Published 2021 May 31. doi:10.3390/nu13061880

Fouré A, Bendahan D.Is branched-chain amino acids supplementation an efficient nutritional strategy to alleviate skeletal muscle damage? A Systematic Review.Nutrients. 2017;9(10):1047. doi:10.3390/nu9101047

University of Rochester Medical Center.Isoleucine.

Xu J, Jakher Y, Ahrens-Nicklas RC.Brain branched-chain amino acids in maple syrup urine disease: implications for neurological disorders.Int J Mol Sci. 2020;21(20):7490. doi:10.3390/ijms21207490

Ko GJ, Obi Y, Tortorici AR, Kalantar-Zadeh K.Dietary protein intake and chronic kidney disease.Curr Opin Clin Nutr Metab Care. 2017;20(1):77-85. doi:10.1097/MCO.0000000000000342

Santos CS, Nascimento FEL.Isolated branched-chain amino acid intake and muscle protein synthesis in humans: a biochemical review.Einstein (Sao Paulo). 2019;17(3):eRB4898. doi:10.31744/einstein_journal/2019RB4898

Neinast M, Murashige D, Arany Z.Branched chain amino acids.Annu Rev Physiol. 2019;81:139-164. doi:10.1146/annurev-physiol-020518-114455

Jackman SR, Witard OC, Philp A, et al.Branched-chain amino acid ingestion stimulates muscle myofibrillar protein synthesis following resistance exercise in humans.Front Physiol. 2017;8:390. doi:10.3389/fphys.2017.00390

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