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Fénix Methode

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Amino acidsWeak evidence

L-leucine

Also known as: leucine

Leucine is an essential branched-chain amino acid (BCAA) that acts as the main trigger for muscle protein synthesis. On its own it is not enough for muscle growth; the other amino acids are needed too.

What it is used for

  • Supporting the muscle response to low-protein meals in older adults – weak to moderate evidence
  • Muscle growth when protein is adequate – weak evidence

Forms and how they differ

L-leucine powder

bitter, poorly soluble; instantised mixes more easily

When to take it

With a meal or protein, especially when the meal is low in protein.

Pairs well with

Complete protein, EAAs, resistance training.

Do not combine / separate

Little point adding it to a meal that already has enough quality protein.

Watch out for

Caution with kidney or liver disease and inherited amino acid disorders. Consult your doctor or pharmacist if you are pregnant, breastfeeding, have kidney or liver disease or take any medicines.

Safety

Do not exceed the label dose.

Practical tip

Leucine works best topping up a plant-based or smaller protein portion, not replacing it.

Products containing L-leucine 2

L-leucine free form 1000 mgfree form · 1 000 mg / servingMusclesRecovery
L-leucine 500 mgfree form · 500 mg / capsuleMusclesRecovery
How to read the evidence rating
Strong evidenceModerate evidenceWeak evidenceNo evidence

Strong = several good human studies or official recommendations; moderate = promising but smaller studies; weak = few studies or mixed results; no evidence = claims not confirmed.

Combination check

Select the supplements you take and, if relevant, your medicines. We show what interferes, what needs a time gap and what to watch out for.

Check L-leucine with others

Which supplements do you actually need?

Fénix Methode picks them from your blood results and schedules when to take what – no needless purchases.

Learn about Fénix Methode

From the same group

Acetyl-L-carnitineWeak evidenceAlmond proteinWeak evidenceAmino acid complexWeak evidenceBCAAWeak evidenceBeef proteinModerate evidenceCaseinStrong evidence
Important notice

This information is educational and does not replace advice from a doctor or pharmacist. We do not give medicine dosages. Supplements are no substitute for a varied diet; if pregnant, breastfeeding, ill or on medication, consult a doctor first.