Last reviewed May 2026 · 1 min read
Is L-Leucine vegan?
Also known as: Leucine, 2-amino-4-methylpentanoic acid
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Source can be plant or animal.
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It depends — Traditionally, L-Leucine was extracted from duck feathers or human hair.
01 · The basics
What is L-Leucine?
An essential branch-chain amino acid (BCAA) used by athletes to stimulate muscle protein synthesis.
02 · The source
Where it comes from
Traditionally, L-Leucine was extracted from duck feathers or human hair. Today, vegan versions produced via bacterial fermentation (of corn or sugar) are common, but many cheap supplements still use animal hair.
03 · Alternatives
Best vegan alternatives
Vegan L-Leucine (fermented)
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Frequently asked
FAQ
Is L-Leucine in supplements vegan?
Not always. Many budget BCAAs are made from bird feathers. Look for 'Vegan' or 'Fermented' on the label to be sure.
Why do athletes take Leucine?
It is considered the most important amino acid for triggering the 'mTOR' pathway, which tells the body to build and repair muscle tissue.
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