Pure L-Leucine

Muscle building & fitness

Function & benefits

The most anabolic amino acid; it acts as the switch for the mTORC1 pathway inside muscle fibres to stimulate protein synthesis, and is especially useful for older adults to counter the age-related decline in anabolic response.

Dosage & how to use

Recommended dose	2.5–4 g per dose
Best time to take	With a low-protein meal or straight after training
Frequency	1–2 times daily

Best forms to choose

Instantized L-leucine made by plant fermentation, to avoid its bitter taste and poor solubility.

Important warnings

Avoid large stand-alone doses over long periods without the other amino acids, to prevent an imbalance in blood isoleucine and valine

Best taken with a complete protein source or with EAA

Drug interactions

Generally safe; it may lower blood sugar slightly by stimulating insulin release, so take care if you use insulin or diabetes medication.

View in the supplements guide

Related supplements

Scientific references

Katsanos CS et al. Am J Physiol Endocrinol Metab 2006 — PMID: 16507602
Jäger R et al. ISSN Position Stand: protein and exercise. J Int Soc Sports Nutr 2017 — PMID: 28642676

📚 Published sources and research: European Food Safety Authority (EFSA) • National Institutes of Health (NIH - ODS) • PubMed / Cochrane databases

Content last updated: 17 October 2026 · Based on published sources and research (EFSA / NIH / PubMed)

⚖️ Medical disclaimer: The information and data provided here are for health education and nutritional guidance only. They are not a medical diagnosis and never replace a direct consultation with your doctor or pharmacist. Always consult your doctor before starting any supplement, especially during pregnancy or breastfeeding or when taking long-term medication.