Isoleucine

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]