Dileucine: The Amino Acid Combo That Outperforms Leucine?
2026-02-17
Leucine has long been hailed as the "anabolic switch" for muscle protein synthesis. It's the critical amino acid that flips the mTOR pathway on, telling your muscles to start building. But what if there was something better?
Enter dileucine—a dipeptide consisting of two leucine molecules bonded together. Emerging research suggests this bonded pair may deliver superior muscle-building effects compared to equivalent doses of free leucine.
What Is Dileucine?
Dileucine (Leu-Leu) is a dipeptide—a chain of two amino acids linked by a peptide bond. When you consume protein, your body breaks it down into individual amino acids and small peptides. Dileucine exists naturally as an intermediate in this breakdown process.
The key advantage: dileucine is transported into muscle cells via a separate mechanism from free amino acids. It uses peptide transporters (PEPT1/PEPT2) rather than competing with other amino acids for absorption. This means more leucine gets into your muscle cells, potentially triggering greater muscle protein synthesis (MPS).
The Research
The Landmark Study
A 2021 study published in the Journal of Applied Physiology put dileucine to the test. Ten healthy young men consumed either 2g of leucine or 2g of dileucine in a randomized crossover design. The results?
Dileucine stimulated significantly greater muscle protein synthesis compared to isomolar leucine. The research demonstrated that dileucine is more effective at promoting muscle protein turnover in young males.2025 Research Updates
More recent research has strengthened these findings. A 2025 study in Journal of the International Society of Sports Nutrition found that dileucine-supplemented essential amino acids (EAAs) and branched-chain amino acids (BCAAs) supported greater whole-body anabolism after resistance exercise compared to control groups.
Perhaps most compelling: research from NNB Nutrition's DL185 compound (a proprietary dileucine formulation) showed 60% greater muscle protein synthesis activation versus equivalent leucine doses, along with significant strength gains.
Lower Body Strength Benefits
A 2025 study in NutraIngredients specifically examined lower body strength and muscular endurance. The results showed dileucine may "significantly increase muscle protein synthesis compared to isomolar amounts of leucine," with researchers noting the muscle boost "translates into meaningful performance benefits."
Why Dileucine Works Better
The science comes down to transport kinetics:
- Separate transporter: Dileucine uses peptide transporters, avoiding competition with free amino acids
- More efficient uptake: Muscle cells may preferentially absorb the dipeptide form
- Sustained release: The bonded structure may provide a more prolonged anabolic signal
Practical Implications
While the research is promising, here's the realistic picture:
- Most studies use 2g doses — equivalent to about 2.6g of leucine
- Timing: Similar to leucine, it appears effective when taken around workouts or with protein
- Form: Dileucine is now available as a standalone supplement (often marketed as DL185 or similar)
- Stacking: It may enhance other amino acid supplements (EAAs, BCAAs, or whey)
The Bottom Line
Dileucine isn't a miracle compound, but the evidence suggests it's genuinely more effective than leucine alone for stimulating muscle protein synthesis. If you're already taking amino acid supplements, dileucine-enhanced products may offer a meaningful upgrade.
The effect size (around 60% greater MPS activation in some studies) is significant in the supplement world. It's not as dramatic as the difference between protein and no protein, but it's meaningful for optimization-focused lifters.
As always, the basics come first: eat sufficient protein (1.6-2.2g/kg bodyweight), train with intensity, and prioritize sleep. Dileucine is an optimization layer on top of that foundation—not a replacement for the fundamentals.
More research is needed on optimal dosing, long-term effects, and comparisons with whole protein sources. But for science-backed supplementStackers, dileucine is one to watch.