Evidence Level
Strong
1 Clinical Trial
4 Documented Benefits
4/5 Evidence Score

DL-185® (NNB Nutrition) is a patented dipeptide consisting of two L-leucine molecules enzymatically bonded together (L-leucyl-L-leucine monohydrate). This structure enables absorption via the PEPT1 peptide transporter — bypassing the saturable passive diffusion pathway of free leucine — delivering 86% more leucine to muscle tissue within 30 minutes versus an equivalent leucine dose. A 10-week double-blind RCT in resistance-trained men demonstrated significantly greater muscle protein synthesis, lower body strength, and muscle endurance vs. both leucine and placebo at just 2 grams/day.

Studied Dose 2,000 mg (2g) once daily; absorbed 185% faster than equivalent leucine dose; clinical RCT: 2g/day × 10 weeks with resistance training
Active Compound L-leucyl-L-leucine monohydrate (dileucine dipeptide) — DL-185® by NNB Nutrition; patented enzymatically bonded di-peptide of two L-leucine molecules

Superior muscle protein synthesis vs. leucine

DL-185® delivers 86% more leucine to muscle tissue within 30 minutes compared to the same dose of free-form leucine, translating to a 60% increase in mean myofibrillar fractional synthetic rate. This outperformance stems from absorption via the PEPT1 dipeptide transporter — an active transport mechanism not subject to the saturation ceiling of free amino acid absorption.

Greater strength gains in clinical RCT

In a 10-week randomized, double-blind, placebo-controlled trial in 34 resistance-trained males, DL-185® produced significantly greater leg press 1RM strength improvements vs. placebo (p=0.02) and outperformed an equivalent leucine dose. Participants following a 4-day/week resistance training program showed meaningful muscle performance advantages with 2g/day dileucine.

Anti-catabolic muscle preservation

DL-185® demonstrates anti-catabolic properties beyond its anabolic MPS stimulation — reducing muscle protein breakdown markers in preclinical studies. This dual anabolic/anti-catabolic profile makes it particularly valuable for cutting phases, aging athletes with anabolic resistance, or periods of caloric restriction where muscle preservation is critical.

Sarcopenia and aging muscle support

Aging muscle is characterized by anabolic resistance — a blunted MPS response to leucine that drives age-related muscle loss. DL-185® bypasses the absorption bottleneck that limits leucine effectiveness in aging muscle, making it one of the few ingredients with a mechanistic rationale for addressing sarcopenia at the amino acid delivery level.

1

PEPT1 dipeptide transporter absorption

Free leucine relies on LAT2 amino acid transporters that become saturated at high concentrations, limiting muscle delivery. DL-185® is absorbed via PEPT1 (peptide transporter 1) — a high-capacity active transporter in the intestinal brush border that handles dipeptides and tripeptides. This separate transport pathway achieves faster, more complete leucine delivery to systemic circulation and muscle tissue.

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mTORC1 pathway activation

Once delivered intramuscularly, dileucine activates the mTORC1 (mechanistic Target of Rapamycin Complex 1) signaling cascade more effectively than free leucine — driving phosphorylation of p70S6K and 4E-BP1, the downstream effectors of muscle protein synthesis. The superior intramuscular leucine delivery achieved by DL-185® produces a stronger and more sustained mTORC1 activation signal.

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Dileucine vs. Leucine RCT — Strength and MPS in Resistance-Trained Males
PubMed

Randomized, double-blind, placebo-controlled trial. 34 resistance-trained males. 2g dileucine vs. 2g leucine vs. placebo × 10 weeks, 4-day/week resistance training. Published in PLOS ONE.

34 resistance-trained males, average age 28.3 ± 5.9 years. 10-week RCT.

Dileucine group showed significantly greater leg press 1RM improvement vs. placebo (p=0.02). Outperformed leucine group on strength and muscle endurance measures. 86% greater intramuscular leucine delivery at 30 min vs. leucine. 60% increase in myofibrillar fractional synthetic rate vs. leucine. No adverse effects reported.

Common Potential side effects

No reported adverse effects in clinical trials at 2g/day
Naturally present in all dietary proteins — well-established safety profile
May be taken with or without food; does not require other ingredients for efficacy

Important Drug interactions

No established drug interactions at clinical dose (2g/day)
mTOR pathway activation — theoretical caution with rapamycin/sirolimus (mTOR inhibitor drugs); consult physician