L-Leucine
The branched-chain amino acid that's the real star of muscle protein synthesis — it's the one that flips the switch to tell your cells to build and repair muscle.
Benefits
- +Stimulates muscle protein synthesis (mTOR pathway)
- +Helps preserve muscle mass, especially during calorie restriction or aging
- +Supports muscle recovery
- +May help with blood sugar regulation (stimulates insulin release)
- +Key component of BCAAs but often more effective alone
Dosage & Cost
The threshold for stimulating muscle protein synthesis is around 2.5–3 g. Many protein powders already contain leucine — check before adding more. Especially important for older adults to maintain muscle mass.
Side Effects
- !Digestive upset or nausea at high doses
- !May lower blood sugar slightly
- !Can worsen symptoms in people with certain metabolic disorders (maple syrup urine disease)
- !Generally safe for most people at recommended doses
Food Sources
- • Whey protein
- • Eggs
- • Chicken and other meats
- • Soybeans
- • Almonds
- • Note: most complete proteins contain leucine — it's most relevant as a supplement for those doing intense training or older adults
References & Links
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This page is for informational purposes only. The information here has not been evaluated by the Food and Drug Administration (FDA). No supplement discussed on this page is intended to diagnose, treat, cure, or prevent any disease. Please consult your doctor or a qualified healthcare professional before taking any dietary supplement.