What Is Dileucine?
42% More Muscle Protein
Synthesis Than Leucine

The Leucine Threshold Problem

Leucine is the most important amino acid for muscle protein synthesis (MPS). It acts as the primary signal that tells your body to shift into an anabolic, muscle-building state. Research has established that there is a "leucine threshold" — a minimum amount of leucine required per meal to maximally stimulate MPS. This is why protein quality matters: proteins with higher leucine content (like whey) are more effective at triggering muscle growth than lower-leucine proteins.

However, free-form leucine has a significant limitation: it is rapidly absorbed and metabolized, creating a brief spike in blood leucine levels followed by a quick return to baseline. This transient signal may not be sufficient to maximally sustain MPS, particularly in older adults or individuals with impaired anabolic sensitivity.

Dileucine — the dipeptide form of leucine — solves this problem through a fundamentally different absorption mechanism.

What Makes Dileucine Different?

Dileucine (leucyl-leucine) is a dipeptide — two leucine molecules bonded together by a peptide bond. This structural difference has profound implications for how it's absorbed and how it affects muscle protein synthesis.

Unlike free-form amino acids, dipeptides are absorbed via a separate, dedicated transport system (PepT1 transporters) that is faster and more efficient than the amino acid transport system. This means dileucine reaches muscle tissue more rapidly and at higher concentrations than an equivalent dose of free leucine. The result is a more potent and sustained anabolic signal.

A landmark 2021 study published in the Journal of Applied Physiology by Paulussen et al. demonstrated this directly: dileucine ingestion elevated plasma leucine concentrations and stimulated muscle protein synthesis significantly more than an equivalent dose of free leucine in young men. The researchers concluded that the dipeptide form was "more effective than leucine in stimulating muscle protein turnover." A 2024 follow-up study extended these findings to lower-body resistance training, confirming that dileucine ingestion increased lower-body strength and MPS markers beyond what leucine alone could achieve.

Key Research Findings

Dileucine vs Leucine: Head-to-Head

Dileucine as Its Own Unmatched Product

Unmatched sells Dileucine as its own standalone product — 2,000mg of L-Leucyl-L-Leucine (DL185®) per serving, dosed separately from CreGAAtine or BH2K rather than folded into either. That's deliberate: dileucine's best-supported research is at rest, taken in the morning or on a non-training day, not timed around a workout the way creatine or a pre-workout stimulant is.

The decision to sell it separately reflects the broader philosophy behind Unmatched Supplements: use advanced, evidence-based ingredients at the dose the research actually used, rather than diluting a headline ingredient across a dozen products at a fraction of the studied amount.

For those focused on longevity and functional fitness — like myself — dileucine's potential relevance to sarcopenia risk is particularly compelling. Maintaining muscle mass as we age is one of the most important predictors of long-term health, mobility, and quality of life. The research so far is strongest at rest, which is exactly the population — older adults, anyone recovering from illness, anyone who can't train — that stands to benefit most from an anabolic signal that doesn't require a workout to trigger it.