Limited evidencePhysical performance

Alpha-Ketoisocaproate (KIC)

The keto acid of leucine, marketed for recovery and anti-catabolic effects. Human data amount to a handful of small trials, and the one positive result used KIC combined with arginine, not KIC alone.

Evidence last reviewed: August 2026

What the science says

Exercise performance Limited evidence
A randomized controlled trial of short-term KIC supplementation found no meaningful improvement in exercise performance. Sample sizes in this literature are in the dozens at most.
High-intensity muscle performance with arginine Limited evidence
An earlier randomized trial reported enhanced high-intensity dynamic muscle performance from a combination of arginine and KIC. Because the two were given together, the contribution of KIC by itself cannot be separated.
Protein metabolism in clinical settings Limited evidence
A randomized controlled study in post-surgical patients compared branched-chain amino acids and KIC on protein metabolism. This is clinical nutrition research and does not transfer to healthy trainees.

Dosage & safety

Studied doseNo established sports dose. Trials used roughly 1.5–3 g/day, often paired with arginine; clinical infusion studies used higher amounts under supervision.

SafetyShort-term oral use in small trials produced no serious adverse effects; gastrointestinal upset is the usual complaint. Long-term safety is unknown, and people with liver or kidney disease should not use keto acid supplements without medical advice.

Scientific references

The effects of short-term alpha-ketoisocaproic acid supplementation on exercise performance: a randomized controlled trial
Yarrow JF, Parr JJ, White LJ — J Int Soc Sports Nutr, 2007
High-intensity dynamic human muscle performance enhanced by a metabolic intervention
Stevens BR, Godfrey MD, Kaminski TW — Med Sci Sports Exerc, 2000
Randomized, controlled study evaluating effects of branched chain amino acids and alpha-ketoisocaproate on protein metabolism after surgery
Sandstedt S, Jorfeldt L, Larsson J — Br J Surg, 1992

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Related in Physical performance

Creatine (monohydrate) Strong evidence
Whey Protein Strong evidence
Caffeine Strong evidence
Beta-Alanine Moderate evidence
BCAA (Branched-Chain Amino Acids) Limited evidence
EAA (Essential Amino Acids) Moderate evidence