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Leucic Acid

Leucic acid (also known as α-hydroxyisocaproic acid or HICA) is a leucine metabolite touted to have anabolic properties. Although it appears to be effective following oral supplementation, comparisons to leucine or HMB do not exist.

Our evidence-based analysis on leucic acid features 14 unique references to scientific papers.

Kamal Patel
Research analysis led by and reviewed by the Examine team.
Last Updated:

Summary of Leucic Acid

Primary information, health benefits, side effects, usage, and other important details

Leucic acid (synonymous with the term α-hydroxyisocaproic acid and the latter's acronym HICA) is a metabolite of the branched chain amino acid known as leucine; leucine initially goes into one of two metabolic pathways (KIC or HMB) and then some of the KIC is further converted into HICA.

HICA is claimed to be an anti-catabolic and anabolic agent similar to HMB. The limited evidence that exists right now (literally one study in athletes and a mention of a pilot study conducted by the same researchers) suggests that there is benefit, but beyond needing replication this study is also confounded.

Although it would be imprudent to say that HICA is ineffective (which it does not appear to be) and similarly imprudent to say that it is worse than HMB or leucine, due to the lack of comparative data between HICA and HMB/leucine the question of 'which one to use' cannot be answered and we have no indication if HICA is better or worse than the other options.

HICA holds some promise for future research to tackle, but currently does not have enough evidence to support its usage as a supplement; it may simply be a more expensive and equally effective leucine.

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How to Take

Recommended dosage, active amounts, other details

The only human evidence currently uses a daily dose of 1,500mg HICA, split into three divided doses of 500mg. There is not enough evidence to suggest if this is the optimal dose nor is there evidence to assess the comparative potency of HICA against leucine or HMB supplementation.

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Human Effect Matrix

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The Human Effect Matrix summarizes human studies to tell you what effects Leucic Acid has on your body, how much evidence there is, and how strong these effects are.

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Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
Notes
grade-c
Lean Mass
Minor - See study
An increase in lean mass has been noted in the legs of soccer players to the degree of 0.4kg over 4 weeks; this study currently stands alone
grade-c
Muscle Soreness
Minor - See study
A decrease in muscle soreness has been noted in the one study conducted in athletes (when measured at week 4 only) to the degree of around 23%, but muscle soreness was not overly high in the study to begin with
grade-c
Weight
Minor - See study
The lone study using leucic acid in athletes has noted a minor but statistically significant increase in weight, attributable to lean mass (muscle plus water; bone mass unchanged)
grade-c
Anaerobic Running Capacity
- - See study
No significant influence on anaerobic running capacity
grade-c
Body Fat
- - See study
No significant interaction between leucic acid and body fat has yet to be detected
grade-c
Bone Mineral Density
- - See study
No significant alterations in bone mineral density
grade-c
Power Output
- - See study
Power output as assessed by jumping tasks and weightlifting is unaffected

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Things to Note

Is a Form Of

Primary Function:

Also Known As

Alpha-Hydroxy-isocaproic acid, DL-alpha-Hydroxy-isocaproic acid, HICA

Do Not Confuse With

Leucine (parent amino acid), HMB (other metabolite)

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This page is regularly updated, to include the most recently available clinical trial evidence.

Each member of our research team is required to have no conflicts of interest, including with supplement manufacturers, food companies, and industry funders. The team includes nutrition researchers, registered dietitians, physicians, and pharmacists. We have a strict editorial process.

This page features 14 references. All factual claims are followed by specifically-applicable references. Click here to see the full set of research information and references for Leucic Acid.

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