Leucine Threshold
Protein Metabolism Nutrition Muscle Building
The leucine threshold is the minimum leucine per meal that reliably initiates muscle protein synthesis (MPS). Practical range: about 2–3 g leucine — commonly reached with ~25–40 g high-quality protein per feeding. For hardgainers that means: plan protein pulses, don’t just tally daily grams.
Notice
Term and Framing
In brief Leucine acts as a trigger amino acid (mTORC1) for MPS. Once the threshold is reached, MPS rises markedly; adding more leucine above the threshold does not yield extra early-phase stimulus. What matters is leucine density per meal and smart distribution across the day.
Scientific Basis (compact)
- Trigger amount: ~2–3 g leucine per meal (often 25–40 g protein, depending on source/matrix).
- Mechanism: Leucine activates mTORC1 → MPS ↑ during the early postprandial window.
- Source matters: Whey, egg, dairy & meats are leucine-dense; plant-based works via combination and slightly larger portions.
Sources and Portion Examples
Rounded reference values — leucine content varies by product. Goal: reach ~2–3 g leucine per feeding.
| Food | Typical portion | Protein ~ | Leucine ~ |
|---|---|---|---|
| Whey isolate | 30 g powder | ~25 g | ~2.7–3.0 g |
| Chicken breast | 120 g cooked | ~35 g | ~2.7–3.0 g |
| Eggs | 3 large | ~18–20 g | ~1.5–1.8 g |
| Skyr/quark (Greek-style yogurt) | 250 g | ~25–27 g | ~2.2–2.6 g |
| Tofu (firm) | 200 g | ~24 g | ~1.9–2.2 g |
| Soy protein isolate | 30 g powder | ~25 g | ~2.1–2.4 g |
| Lentils (cooked) | 300 g | ~24 g | ~1.7–2.0 g |
Practice Setup for Hardgainers
- Protein pulses: 3–5 meals providing 25–40 g protein each (≥2 g leucine), aligned with SRA windows around hard sessions.
- Pre/Intra/Post: Leucine-dense choices pre & post (whey/quark/meat/soy isolate); intra: hydration/salt, optionally targeted carbs.
- Couple energy: Lean Surplus (~+250–400 kcal) and describe RoG at ~0.25–0.5%/week rather than dictating it.
- Monitoring: 7-day average body mass, strength progression, tolerability (Food Hygiene), sleep.
Common Mistakes
- Counting only daily protein: MPS is triggered per meal — plan pulses instead of “dumping” at night.
- Tiny snacks: 10–15 g protein often miss the threshold → bundle or add to reach it.
- Plant-based without planning: use combos & slightly larger portions to hit 2–3 g leucine.
“You have to get fat to gain weight”
False. Lean Surplus over dirty bulking: smarter calories, clean macros, Food Hygiene & monitoring. Details: Myth Busting — Myth #5.
Interactive Leucine Threshold – MPS Response per Meal
Input – your meal
Leucine threshold – visualization
The calculation uses simplified assumptions: roughly 10 % leucine content in a higher-quality protein source (e.g. whey) and an idealized dose–response curve. This is an orientation framework, not a rigid prescription – individual differences and your total daily protein intake still matter.
Studies and evidence (PubMed)
If you want to dive deeper into the research on the leucine threshold and muscle protein synthesis, here is a small selection of studies on PubMed:
- Leucine supplementation improves muscle protein synthesis in elderly men independently of hyperaminoacidaemia – The Journal of Physiology, 2006
- Long-term leucine supplementation does not increase muscle mass or strength in healthy elderly men – American Journal of Clinical Nutrition, 2009
Note: These studies are primarily aimed at professionals and do not replace medical advice.
Hardgainer Supplement Guide – must-haves, nice-to-haves & special-purpose supplements
🧪 Open Hardgainer Supplement GuideFurther Reading
- Protein • MPS • Lean Surplus • Rate of Gain
- Maintenance Calories • NEAT • SRA • MEV • RIR • RPE