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What is isoleucine?

Isoleucine is an essential amino acid and one of the three branched-chain amino acid (BCAA) [1]. In foods, isoleucine is incorporated into proteins.

Isoleucine abbreviation (symbol): Ile

Isoleucine Functions in the Human Body

Isoleucine is:

  • Important for synthesis of hemoglobin and other proteins, detoxification of nitrogen wastes, wound healing and immunity [1]
  • A glucogenic amino acid — it can be converted into glucose [11] 
  • A ketogenic amino acid — it can be converted into ketones [11]

Foods Rich in Isoleucine

  • ANIMAL FOODS: pork, beef, veal, lamb, chicken, turkey, fish, cheese [2]
  • PLANT FOODS: wheat germ, legumes, seeds and baker’s yeast [2]

Foods low in isoleucine: cereals (except wheat germ), fruits and vegetables [2].

Isoleucine Deficiency

Isoleucine deficiency can occur due to the isoleucine-free diet in a maple syrup urine disease, methylmalonic acidemia, propionic acidemia [6]. Deficiency can affect eye cornea (vision disturbance), skin (dermatitis) and intestinal lining (diarrhea) [3,4].

Isoleucine Supplements

Oral L-isoleucine supplements without prescription (over-the-counter) are available.

Possible Isoleucine Supplements Benefits

Isoleucine supplements are PROBABLY INEFFECTIVE in the prevention or treatment of hot flushes in postmenopausal women [5].

There is INSUFFICIENT EVIDENCE about the effectiveness of isoleucine supplements in:

  • Increasing muscle mass or improving athletic performance (see branched-chain amino acids)
  • Prevention of essential amino acid deficiency in individuals on protein-restricted diets, such as in methylmalonic acidemia, propionic acidemia and maple syrup urine disease [6]
  • Reduction of acute diarrhea in children, when added to oral rehydration solution [7]

Isoleucine Safety: Side Effects, Toxicity

The safety of isoleucine supplements is described under branched-chain amino acids.

Who should limit isoleucine intake?

Individuals with the following conditions should limit isoleucine intake from foods and supplements:

  • Maple syrup urine disease [8]
  • Methylmalonic acidemia [9]
  • Propionic acidemia [10]

  1. L-Isoleucine  PubChem
  2. List of foods high in isoleucine  US Department of Agriculture
  3. Giacoia GP et al, 1993, Acrodermatitis enteropathica-like syndrome secondary to isoleucine deficiency during treatment of maple syrup urine disease  PubMed
  4. Tornqvist K et al, 1996, Corneal deepithelialization caused by acute deficiency of isoleucine during treatment of a patient with maple syrup urine disease  PubMed
  5. Guttuso T et al, 2008, Effects of L-isoleucine and L-valine on hot flushes and serum homocysteine: a randomized controlled trial  PubMed
  6. van Vliet D et al, 2014, Single amino acid supplementation in aminoacidopathies: a systematic review  PubMed Central
  7. Alam NH et al, 2011, L-isoleucine-supplemented Oral Rehydration Solution in the Treatment of Acute Diarrhoea in Children: A Randomized Controlled Trial  PubMed Central
  8. Maple syrup urine disease  MedlinePlus
  9. Methylmalonic acidemia  MedlinePlus
  10. Propionic acidemia, dietary treatment  Emedicine
  11. Amino acid  ChemPep

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