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Leucine

Other name(s):

a-amino-isocaproic acid

Unsubstantiated claims

There may be benefits that have not yet been proven through research.

Leucine is one of the 3 branched chain amino acids. These amino acids can be used by skeletal muscle to give energy during exercise. Eating foods that have complete protein gives enough of these amino acids. This includes foods such as meat, poultry, fish, eggs, and milk. Results of studies have not been reliable in showing that taking supplements of these amino acids improves exercise performance, or builds muscle mass, or helps you recover from exercise. Leucine may help healing of skin and bones. It may increase muscle growth and lean body mass. It may increase production of human growth hormone (HGH). It may help control blood sugar.

Recommended intake

Amino acids (AAs) are available as single AAs or in AA combinations. They also come as part of multi-vitamins, proteins, and food supplements. The forms include tablets, fluids, and powders.

By eating enough protein in your diet, you get all of the amino acids you need.

You should take leucine supplements with valine and isoleucine.

There are no conditions that increase how much leucine you need.

Side effects, toxicity, and interactions

Using a single amino acid supplement may lead to negative nitrogen balance. This can lessen how well your metabolism works. It can make your kidneys work harder. In children, single amino acid supplements may cause growth problems.

You should not take high doses of single amino acids for long periods of time.

Very high doses of leucine may cause low blood sugar (hypoglycemia). It may also cause pellagra. Symptoms of this can include skin lesions, hair loss, and gastrointestinal problems.

Women who are pregnant or breastfeeding shouldn’t use leucine supplements. People who have maple syrup urine disease (MSUD), a rare inherited issue, shouldn’t take either. They also shouldn’t take the other branched-chain amino acids. These include isoleucine and valine.

Online Medical Reviewer: Cynthia Godsey
Online Medical Reviewer: Diane Horowitz MD
Online Medical Reviewer: Rita Sather RN
Date Last Reviewed: 3/1/2019
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