Alpha-ketoisocaproic acid

Other Names

2-keto-4-methyl-pentanoate2-Keto-4-methylpentanoic acid2-keto-4-Methylvaleric acid2-Ketoisocaproate2-Ketoisocaproic acid2-Ketoisocapronic acid2-Oxo-4-methylpentanoate2-Oxo-4-methylpentanoic acid2-Oxo-4-methylvalerate2-Oxo-4-methylvaleric acid2-Oxoisocaproate2-Oxoisocaproic acid2-Oxoleucine4-methyl-2-oxo-pentanoic acid4-methyl-2-Oxopentanoate4-Methyl-2-oxopentanoic acid4-methyl-2-Oxovalerate4-Methyl-2-oxovaleric acid4-MOPalpha-KetoisocaproateKetoleucineKICPentanoic acid, 4-methyl-2-oxo-α-Ketoisocaproateα-Ketoisocaproic acidα-KICα-oxoisocaproateα-oxoisocaproic acid

Synopsis

Alpha-Ketoisocaproic Acid (α-KIC): A Comprehensive Reference

1. Identity, Nomenclature, and Chemical Profile

α-Ketoisocaproic acid (α-KIC), also known as 4-methyl-2-oxovaleric acid, and its conjugate base and carboxylate, α-ketoisocaproate, are metabolic intermediates in the metabolic pathway for L-leucine. Additional synonyms found in the biomedical literature include 2-oxoisocaproic acid and, more informally, ketoleucine. The compound is abbreviated throughout the research literature as KIC or α-KIC.

This compound is a branched-chain keto acid and a ketogenic compound. Structurally, it is the α-keto analogue of the essential branched-chain amino acid (BCAA) L-leucine: the amino (–NH₂) group at the α-carbon is replaced by a ketone (=O) group, while the branched isobutyl side chain is retained. Its molecular formula is C₆H₁₀O₃, and its molecular weight is approximately 130.14 g/mol.

Common Forms and Preparations

α-KIC does not exist to a clinically significant extent as a discrete food ingredient; it is primarily encountered endogenously as a normal product of leucine catabolism. In research and nutritional/clinical contexts, it has appeared in several formulations:

Free acid form: Used in biochemical and some early clinical studies.
Calcium or sodium salt: The most pharmaceutically relevant form; included in compound ketoanalogue tablets (e.g., Ketosteril®, Alphaket®), which are multi-ingredient preparations containing the keto analogues of several essential amino acids alongside hydroxy analogues.
Glycine-arginine salt (GAKIC): The physiological effects of GAKIC treatment likely affect metabolic pathways individually or synergistically associated with the components of the conjugated salt comprising L-arginine, glycine, and KIC as the ketoacid parent of the branched-chain amino acid L-leucine.
Combined HMB/KIC preparations: Used in some sports nutrition clinical trials.

KIC, used as a nitrogen-free substitute for leucine, could serve as an integral part of therapy for chronic kidney disease and hepatitis B virus infection to provide patients with their daily requirement of L-leucine. With the application of KIC in the food, feed, and pharmaceutical industries, considerable efforts have been devoted to the mass production of KIC.

2. Natural Sources and Endogenous Occurrence

Leucine is an essential amino acid, and its degradation is critical for many biological duties. α-KIC is produced in one of the first steps of the pathway by branched-chain amino acid aminotransferase by transferring the amine on L-leucine onto alpha-ketoglutarate, and replacing that amine with a ketone.

The first reaction in the pathway of HMB synthesis in the body is the reversible transamination of leucine to alpha-ketoisocaproic acid (KIC) by BCAA aminotransferase. This reaction primarily occurs in skeletal muscle. Because the activities of the next enzymes in leucine catabolism [branched-chain alpha-keto acid dehydrogenase (BCKD) and KIC dioxygenase] are low in skeletal muscle, most of the KIC is released from the muscles into the blood and is further metabolized in various tissues.

α-KIC is not a discrete "botanical" ingredient—it is not derived from any single plant species—but is rather a normal endogenous metabolite arising wherever L-leucine-containing proteins are catabolized. Dietary protein from any leucine-rich food (meat, dairy, legumes, eggs) will give rise to circulating α-KIC as part of normal amino acid catabolism. The branched-chain ketoacids (BCKAs) are used as dietary supplements to spare essential amino acid nitrogen, yet little is known about their absorption and utilization in the body.

A structurally related compound, α-hydroxyisocaproic acid (HICA, also called leucic acid), is a reduction product of α-KIC. Foods that are produced by fermentation, such as some cheeses, may contain small amounts of HICA. HICA is a reduction product of the α-keto acid analogue of leucine, α-ketoisocaproic acid (KICA), and as such contributes to the free pools of branched-chain amino acids (BCAA).

3. Historical and Clinical-Nutritional Context

Unlike many traditional herbal supplements, α-KIC has no recorded use in classical herbalism, folk medicine, or any specific traditional healing system. Its significance in human nutrition is entirely a product of modern biochemistry and clinical nutrition research, developed over the latter half of the twentieth century.

In the early to mid-20th century, KIC began to attract attention for its role in clinical nutrition, especially in the management of metabolic disorders such as urea cycle defects and certain forms of hepatic encephalopathy. It was found to help reduce ammonia accumulation in the body by acting as an alternative nitrogen acceptor, thereby supporting cognitive function and overall metabolic balance.

The systematic scientific use of keto acid analogues—including α-KIC—in chronic kidney disease management was pioneered primarily by European and American clinical nutrition researchers during the 1970s and 1980s, building on foundational work on nitrogen metabolism. The rationale centered on providing essential amino acid equivalents to patients on severely protein-restricted diets while minimizing uremic nitrogen waste accumulation. Alpha-ketoisocaproic acid is an amino acid used to manage chronic renal failure and for nutritional therapy in acute renal dysfunction.

Historically, KIC has been explored for its potential roles in muscle metabolism, energy production, and as an anti-catabolic agent. The rationale for its supplementation stems from its involvement in the leucine metabolic pathway, where it serves as both a precursor and a byproduct, potentially influencing muscle protein synthesis and reducing muscle breakdown.

4. Key Constituents, Biochemistry, and Mechanisms of Action

4.1 Position in Leucine Catabolism

α-KIC is produced in one of the first steps of the pathway by branched-chain amino acid aminotransferase by transferring the amine on L-leucine onto alpha-ketoglutarate, and replacing that amine with a ketone. The degradation of L-leucine in the muscle to this compound allows for the production of the amino acids alanine and glutamate as well. In the liver, α-KIC can be converted to a vast number of compounds depending on the enzymes and cofactors present, including cholesterol, acetyl-CoA, isovaleryl-CoA, and other biological molecules. Isovaleryl-CoA is the main compound synthesized from α-KIC.

An alternate, cytosolic oxidative pathway in the liver converts α-KIC to beta-hydroxy-beta-methylbutyrate (HMB) via the enzyme KIC dioxygenase (also called KIC oxygenase). This alternate oxidative pathway occurs in the cytosol and involves oxidation of KIC to beta-hydroxy-beta-methylbutyrate (HMB) by the enzyme KIC-oxygenase. HMB itself has attracted substantial independent research interest as an anti-catabolic and muscle-protective compound.

4.2 Protein Synthesis Signaling (mTORC1)

Although KIC can activate mTORC1, stimulate the protein synthesis pathway, and induce insulin secretion, much less is known about its direct effect on insulin action in skeletal muscle, except for a study that showed that at supraphysiological concentrations (up to 2 mM) KIC stimulates glucose transport in skeletal muscle.

Animal research has confirmed that α-KIC signals through the mTOR pathway. Administration of leucine and KIC resulted in greater (P < 0.006) phosphorylation of eukaryotic initiation factor (eIF) 4E binding protein-1 (4E-BP1) in skeletal muscle of neonatal pigs—a key step in translational initiation. KIC could also play multifunctional roles in metabolic regulation and thereby reduce protein catabolism, stimulate protein synthesis, and promote insulin secretion.

4.3 Insulin Secretion

When all K(ATP) channels were closed by the sulfonylurea glipizide, alpha-keto acid anions amplified the insulin release in the order beta-phenylpyruvate < alpha-ketoisovalerate < alpha-ketovalerate ≈ alpha-ketocaproate < alpha-ketoisocaproate. This difference from the above orders indicates that direct K(ATP) channel inhibition moderately contributes to initiation of insulin secretion by alpha-ketoisocaproate and alpha-ketocaproate. Additionally, α-KIC acts as a mitochondrial substrate in pancreatic beta-cells, entering oxidative pathways that elevate the ATP/ADP ratio and thereby depolarize the beta-cell membrane to trigger calcium influx and insulin release.

4.4 Nitrogen Metabolism and Transamination

Because the transamination reaction producing α-KIC from leucine is reversible, α-KIC can accept an amino group from glutamate (or other amino acid donors) and re-form leucine. This reversibility is central to its clinical use as a nitrogen-sparing agent: administered α-KIC can incorporate nitrogenous waste (as an amino group donor), thereby reducing systemic ammonia and urea accumulation. Due to the lack of an amino group in the chemical structure, KAs can be utilized in place of their respective amino acids without releasing nitrogen waste products into the body.

4.5 Insulin-Stimulated Glucose Transport — A Dual Role

The effects of leucine on insulin-stimulated glucose transport and activation of mTORC1 in skeletal muscle cells were modulated by the presence of other amino acids in the incubation medium. Importantly, KIC inhibited insulin-stimulated glucose transport and this required mTORC1 activity. In cells depleted of BCAT2, the effect of KIC was abrogated. This finding indicates a context-dependent, BCAT2-mediated mechanism whereby high KIC concentrations may impair insulin action, with implications for metabolic disease risk.

5. Pharmacokinetics and Bioavailability

A stable-isotope tracer study by Matthews et al. (1999) characterized the fate of enterally delivered α-KIC in humans. To study the fate of enterally delivered α-ketoisocaproate (KIC), seven healthy adults were infused in the postabsorptive state with [1-¹³C]KIC and [phenyl-²H₅]phenylalanine intravenously and with [5,5,5-²H₃]KIC by nasogastric tube. The branched-chain ketoacids are used as dietary supplements to spare essential amino acid nitrogen, yet little is known about their absorption and utilization in the body.

The fraction of enterally delivered tracer sequestered by the splanchnic bed on the first pass was 30.9% ± 2.0%, 30.0% ± 1.4%, and 30.7% ± 2.7% for ¹³C-KIC, ²H₃-KIC, and ²H₅-phenylalanine, respectively. This indicates that approximately one-third of orally delivered α-KIC is extracted by the splanchnic bed before reaching systemic circulation. The fraction of infused ¹³C-KIC tracer recovered as ¹³CO₂ was 27.1% ± 1.2% and 24.0% ± 0.9% during IV and NG infusion, respectively. From these data, the fraction of NG KIC tracer extracted and oxidized on the first pass was calculated to be 5.1% ± 1.1%.

Research on the production of KIC from dietary leucine in the fed state further illuminates interorgan metabolism. 26% ± 5% of the orally administered leucine was taken up by the splanchnic organs at first pass, whereas 74% ± 5% appeared in the systemic circulation. The rate of splanchnic KIC release from deamination of dietary leucine accounted for 3% ± 0.2% of the oral leucine administration rate and 13% ± 2% of leucine splanchnic uptake (fractional splanchnic deamination).

6. Scientific Evidence by Area of Use

6.1 Chronic Kidney Disease (CKD) and Low-Protein Diet Support

This is the area with the strongest and most extensive clinical evidence for α-KIC and related ketoanalogues. α-KIC is one of the active constituents in compound ketoanalogue tablet formulations used alongside very low-protein diets (VLPDs) in CKD management.

According to the updated Kidney Disease Outcomes Quality Initiative (KDOQI) nutrition guideline, a very low protein diet (VLPD) providing 0.3–0.4 g dietary protein/kg/day supplemented with ketoanalogues (KAs) of essential amino acids may be considered as another dietary regimen to reduce the risk of ESKD.

In a study of 81 patients with CKD and 116 patients with non-diabetic CKD, supplemented VLPDs were observed to be safe and have metabolic/nutritional benefits in both groups with respect to reduction of serum urea, phosphorus levels, and fasting glucose levels as well as nutritional markers including serum albumin, cholesterol, body weight, BMI, and muscle strength.

A large retrospective cohort study provided outcome data on keto acid use in advanced CKD. In a study of stage 5 NDD-CKD patients with diabetes, the five-year mortality rate was 27% lower among keto acid users (N = 1,001) vs. keto acid non-users (N = 14,781). This study also found that the incidence of ESKD and major adverse cardiovascular events among keto acid users was decreased by 35% and 23%, respectively, compared to keto acid non-users.

There was progressive improvement in clinical features in both groups after 12 weeks of treatment, but the KAA group showed more marked improvement compared with the control group. Both groups showed gradual improvement in the biochemical parameters compared to their pre-treated values, which was more marked in the KAA-supplemented group. There was a reduction in blood glucose, blood urea, serum creatinine, and 24-hour total urine protein. There was an increase in hemoglobin, 24-hour total urine volume, and glomerular filtration rate.

Regarding dosage used in CKD protocols, with a VLPD approach, the full dose of additional KAs containing 0.125 g of keto acids/kg/day (approximately one tablet per 5 kg per day) has been suggested to meet the minimal protein requirement in pre-dialysis CKD patients. Previous randomized controlled studies among non-diabetic CKD populations have reported that the rate of CKD progression and dialysis initiation in patients receiving VLPD supplemented with KAs, corresponding to up to 12 tablets/day, was significantly lower than in the LPD group.

A clinical trial investigating the effect of LPD + ketoacids on muscle wasting in CKD found that this study did not find a significant improvement of KAs on muscle wasting, and a long time or more indices study may need to find the effects of the LPD + KA diets. This illustrates that while CKD disease-slowing evidence is relatively strong, specific outcomes such as muscle mass preservation remain less conclusively demonstrated.

The anti-fibrotic and anti-inflammatory mechanisms of compound α-keto acid tablets have also been studied. Keto-analogue administration plays an important role in clinical CKD adjunctive therapy; however, previous studies on their reno-protective effect mainly focused on kidney pathological changes induced by nephrectomy. One study was designed to explore the alternative mechanisms by which compound α-ketoacid tablets influenced ischemia–reperfusion induced murine renal injury, and to probe the current status of KA administration on staving CKD progression in Chinese CKD patients at different stages.

Evidence strength for CKD: Moderate to strong for slowing CKD progression and reducing nitrogenous waste markers when α-KIC-containing compound tablets are used as part of VLPD management. Evidence comes from multiple RCTs, cohort studies, and clinical trials, though α-KIC is rarely studied in isolation—it is typically one component of a multi-ingredient ketoanalogue formulation.

6.2 Skeletal Muscle Protein Synthesis and Anti-Catabolism

Several studies indicate that free branched-chain amino acids (BCAAs), especially leucine, and their transaminated metabolites, such as α-ketoisocaproic acid (KIC), may alleviate symptoms associated with exercise-induced catabolism.

In a controlled animal study, infusion of leucine, alpha-ketoisocaproic acid (KIC), and norleucine (0 or 400 micromol kg⁻¹ h⁻¹ for 60 min) on protein synthesis and activation of translation initiation factors in piglets showed that infusion of leucine, KIC, and norleucine raised plasma levels of each compound compared with controls. KIC also increased plasma levels of leucine. Administration of leucine and KIC resulted in greater phosphorylation of eukaryotic initiation factor (eIF) 4E binding protein-1 (4E-BP1). This study provides mechanistic support for KIC's protein synthesis-stimulating activity but is limited to an animal model.

An early animal study found that addition of alpha-ketoisocaproic acid in place of leucine to a leucine-free diet also prevented loss of body weight. Efficiency of such substitution varied from 27% for a diet containing 84.6 micromoles of alpha-ketoisocaproic acid/g to 20% for a diet containing 169.2 micromoles alpha-ketoisocaproic acid/g.

Evidence strength for muscle protein synthesis: Predominantly preclinical (animal and cell-based). Direct human clinical evidence for α-KIC as an isolated muscle anabolic agent is limited.

6.3 Exercise Performance — KIC Monotherapy

A randomized, double-blind, placebo-controlled crossover trial specifically examined the effect of KIC alone on resistance exercise performance. Thirteen resistance-trained men (22.8 ± 2.5 years; 81.6 ± 12.6 kg) participated in a prospective, randomized, double-blind, placebo-controlled crossover experiment. Each subject completed one familiarization and four experimental trials with either 1.5 g or 9.0 g of either KIC or isocaloric placebo control, following an overnight fast. During the experimental trials, subjects consumed the supplement regimen and then completed leg and chest press repetitions to failure and 30 s of repeated maximal vertical jumping on a force plate.

No significant differences (p > 0.05) were observed between dosages or conditions for leg press. The authors concluded that short-term KIC monotherapy at either 1.5 g or 9.0 g had no significant ergogenic effect on moderate- or high-intensity single-bout exercise performance in trained men.

Evidence strength for KIC monotherapy and exercise performance: One small RCT (n = 13); result was negative. Evidence does not support acute ergogenic benefit from isolated KIC supplementation in resistance-trained individuals.

6.4 Exercise Performance — GAKIC (Compound Preparation)

A more investigated area involves α-KIC as part of the compound supplement glycine-arginine-α-ketoisocaproic acid (GAKIC). Stevens et al. initiated studies that revealed a particular glycine and L-arginine salt of alpha-ketoisocaproic acid (GAKIC) that significantly enhanced human muscle dynamic performance in an isolated quadriceps model of intense, exhaustive, anaerobic exercise. Those studies involved simultaneously applied concentric plus eccentric fatigue to the point of complete exhaustion in each bout, as quantified by cycle dynamometry.

A peer-reviewed RCT published in Medicine & Science in Sports & Exercise (Buford & Koch, 2004) found: Ten men completed a randomized, double-blinded, placebo-controlled exercise protocol of two sessions separated by 7 d. Subjects consumed either 11.2-g GAKIC or placebo during a 45-min period between the REST and exercise. Mean power, peak power, and fatigue values were assessed from five supramaximal, 10-s cycle ergometer sprints, separated by 1-min rest intervals. Post hoc analyses revealed a greater retention of mean power (P = 0.038) between sprints 1 and 2 after GAKIC (−1 ± 9 W) versus PLC treatment (−47 ± 18 W). No other performance variables differed between PLC and GAKIC. POST lactate was increased (P < 0.001) above REST, but there was no difference between treatments. These data support an ergogenic effect of GAKIC for attenuating the decline in mean power during repeated bouts of supramaximal exercise.

However, a subsequent study by Peltonen et al. (2011) in International Journal of Sport Nutrition and Exercise Metabolism failed to replicate these findings in trained athletes. The aim was to examine the effects of GAKIC supplementation on fatigue during high-intensity, repeated cycle sprints in trained cyclists. After at least 2 familiarization trials, 10 well-trained male cyclists completed 2 supramaximal sprint tests each involving 10 sprints of 10 s separated by 50-s rest intervals. Subjects ingested 11.2 g of GAKIC or placebo during a period of 45 min before the 2 experimental trials, administered in a randomized and double-blind fashion. Peak power declined from the 1st sprint to the 10th sprint and did not differ between conditions (p = .88). Mean power declined similarly and did not differ between conditions (p = .96). The fatigue index remained at ~38% throughout the series of sprints and did not differ between conditions (p = .99). In contrast to previous studies in untrained individuals, these results suggest that GAKIC has no ergogenic effect on repeated bouts of high-intensity exercise in trained individuals.

Evidence strength for GAKIC and exercise performance: Mixed. Initial small RCTs in untrained or recreationally active subjects showed a modest benefit in power retention during repeated anaerobic sprints; a subsequent study in trained cyclists found no benefit. The total number of study participants across all GAKIC studies remains small. Because GAKIC is a compound, any effect cannot be attributed solely to α-KIC.

6.5 Exercise-Induced Muscle Damage — Combined HMB/KIC

One clinical trial studied the combination of HMB and KIC (not KIC alone) in the context of exercise-induced muscle damage. This study examined the effects of beta-hydroxyl-beta-methylbutyrate (HMB) and alpha-ketoisocaproic acid (KIC) supplementation on signs and symptoms of exercise-induced muscle damage following a single bout of eccentrically biased resistance exercise. Six non-resistance trained male subjects performed an exercise protocol designed to induce muscle damage on two separate occasions, performed on the dominant or non-dominant arm in a counter-balanced crossover design. Subjects were assigned to an HMB/KIC (3 g HMB and 0.3 g alpha-ketoisocaproic acid, daily) or placebo treatment for 14 d prior to exercise. One repetition maximum (1RM), plasma creatine kinase activity (CK), delayed onset muscle soreness (DOMS), limb girth, and range of motion (ROM) were determined pre-exercise, at 1h, 24 h, 48 h, and 72 h post-exercise.

This study (van Someren et al., 2005, PMID 16286672) reported a reduction in signs and symptoms of exercise-induced muscle damage with the HMB/KIC combination. However, a larger follow-up study from Oxford (Nunan, Howatson & van Someren, 2010) failed to replicate this finding. The purpose of this study was to examine the effects of combined oral beta-hydroxy-beta-methylbutyrate (HMB) and alpha-ketoisocaproic acid (KIC) supplementation on indices of exercise-induced muscle damage after an acute bout of eccentric-biased exercise. Fourteen male subjects were allocated to 2 groups: a placebo group (3 g/d corn flour, N = 7) or an HMB + KIC group (3 g/d HMB and 0.3 g/d KIC, N = 7). Supplementation commenced 11 days before a 40-minute bout of downhill running.

Evidence strength for HMB/KIC and muscle damage: Conflicting. Two small clinical trials produced opposite results. No conclusion can be drawn about KIC's specific independent contribution, as it was always co-administered with a larger dose of HMB (3 g HMB vs. 0.3 g KIC).

6.6 Insulin Secretion and Glucose Metabolism

High concentration of the leucine metabolite, α-ketoisocaproic acid (KIC), is associated with insulin resistance and T2DM in humans and animals. This observation must be interpreted carefully: it reflects associations seen at pathologically elevated concentrations (as in untreated MSUD or experimental models), not at supplementation doses. The underlying mechanisms studied in vitro and in animal models indicate a complex, concentration-dependent relationship:

At physiological-to-moderate concentrations, α-KIC stimulates insulin secretion via mitochondrial metabolism and partial KATP channel closure in pancreatic beta-cells.
At higher concentrations, KIC inhibited insulin-stimulated glucose transport and this required mTORC1 activity.

No dedicated human RCTs examining α-KIC supplementation specifically for insulin secretion or glycemic control as a primary outcome have been identified in the peer-reviewed literature. Some CKD studies measuring blood glucose as a secondary endpoint report reductions, but this is in the context of compound keto acid formulations, not isolated KIC.

Evidence strength for glycemic effects: Predominantly in vitro and animal-based. Human evidence is indirect (from CKD trials using compound formulations). The dual stimulatory-at-low/inhibitory-at-high concentration profile adds interpretive complexity.

7. Body Systems and Health Areas Associated with α-KIC

Renal System: Most clinically relevant; used in compound ketoanalogue tablets for CKD nitrogen management. Multiple RCTs and cohort studies support slowed CKD progression when used as part of a VLPD protocol.
Skeletal Muscle / Musculoskeletal System: Implicated in muscle protein synthesis via leucine-like mTORC1 activation; anti-catabolic interest in exercise and trauma nutrition. Human evidence is limited and mixed.
Metabolic / Endocrine System: Stimulates insulin secretion from pancreatic beta-cells via mitochondrial substrate oxidation; high concentrations may impair insulin-stimulated glucose uptake in muscle via mTORC1-BCAT2 axis.
Neurological System (Toxicological Context): At pathologically elevated levels (as in MSUD), α-KIC is considered a key neurotoxic metabolite. This is a disease-state consideration, not a feature of normal supplementation.
Hepatic System: The liver is a major site of α-KIC catabolism, converting it to isovaleryl-CoA, acetyl-CoA, cholesterol, and HMB.

8. Dosage Forms and Reported Study Dosages

The following dosages are drawn directly from published clinical and experimental research, reported as stated in those sources:

KIC monotherapy (exercise performance, acute): 1.5 g or 9.0 g of KIC, consumed following an overnight fast.
HMB/KIC combination (muscle damage, 14 days): 3 g HMB and 0.3 g alpha-ketoisocaproic acid, daily.
HMB/KIC combination (muscle damage, 11 days before exercise): 3 g/d HMB and 0.3 g/d KIC.
GAKIC compound supplement (anaerobic exercise): 11.2-g GAKIC consumed during a 45-min period before exercise. This formulation contains approximately 3.2 g KIC, 6.0 g glycine, and 2.0 g L-arginine per serving, based on referenced GAKIC literature.
Compound ketoanalogue tablets (CKD, VLPD): Full dose of additional KAs containing 0.125 g of keto acids/kg/day (approximately one tablet per 5 kg per day). The daily dose of keto-/amino acid for each patient is one tablet every 5 kg body weight. The total daily dose is divided into three times a day.
Compound ketoanalogue tablets (CKD, LPD): A supplementation of full-dose KAs containing 0.125 g of keto acids/kg/day or one tablet per 5 kg has been commonly employed in the VLPD approach.

9. Safety Considerations and Interactions

9.1 Safety in Healthy Individuals at Supplemental Doses

Multiple studies have demonstrated no adverse effects on humans or animals that ingested alpha-ketoisocaproic acid or its derivatives. However, in patients with MSUD who are unable to metabolize branched-chain alpha-keto acids, alpha-ketoisocaproic acid is believed to be one of the key mediators of neurotoxicity.

In the exercise performance RCT at doses of 1.5 g and 9.0 g: During the study, two subjects reported gastrointestinal distress during both the high-dose sucrose placebo and high-dose KIC trials. The performance of these two subjects was analyzed separately and appeared consistent with the remaining subjects. This suggests gastrointestinal discomfort is a possible adverse effect at higher doses, though it also occurred with the placebo in this case.

9.2 Neurotoxicity at Pathologically Elevated Levels

This is relevant as a safety consideration for individuals with inborn errors of BCAA metabolism, not for typical supplementation in metabolically normal individuals:

Elevated leucine and alpha-ketoisocaproic acid levels notoriously cause neurochemical disturbances, resulting in clinically apparent neurotoxicity. Neurotoxicity is aggravated by the metabolic decompensation in MSUD, which activates matrix metalloproteinases, resulting in the further breakdown and dysfunction of the blood-brain barrier.

High intracranial leucine concentrations compete with the cerebral uptake of several other important amino acids, particularly phenylalanine, glutamine, histidine, methionine, and tryptophan, negatively impacting brain growth, neurotransmitter production, and myelin synthesis. The restricted supply of essential amino acids leads to decreased neurotransmitters, including dopamine, serotonin, norepinephrine, epinephrine, GABA, and glutamate.

Alpha-ketoisocaproic acid levels greater than 60 mmol/L negatively affect astrocyte transamination reactions. This restriction causes low cerebral glutamate levels, which results in cognitive dysfunctions (e.g., learning disabilities and memory loss). These critical neurotoxic effects are described in the context of MSUD, a condition where the BCKAD enzyme complex is non-functional, causing pathological accumulation far beyond any foreseeable supplementation-derived level.

KIC reduced the cells' metabolic ability to reduce MTT and increased reactive species production in hippocampal neurons. Impairment in hippocampal mitochondrial function seems to be involved in the neurotoxicity induced by KIC. Again, this was demonstrated in intracerebroventricular injection models at supraphysiological concentrations.

9.3 Insulin and Glycemic Interactions

High concentration of the leucine metabolite, α-ketoisocaproic acid (KIC), is associated with insulin resistance and T2DM in humans and animals. The mechanistic basis for this, as determined in cell-based studies, is that KIC inhibited insulin-stimulated glucose transport and this required mTORC1 activity. The clinical relevance of this at supplementation doses in normoglycemic individuals has not been well established in human trials.

9.4 Contraindication: Maple Syrup Urine Disease

Maple Syrup Urine Disease (MSUD) is a rare genetic disorder caused by a deficiency in the branched-chain alpha-ketoacid dehydrogenase complex, leading to the accumulation of branched-chain amino acids and their toxic byproducts. This condition is detectable in newborn screenings due to its severe impact on development if left untreated. Any additional α-KIC loading would be contraindicated in individuals with MSUD.

9.5 Safety in CKD Populations

There was no statistical difference in the two groups with respect to side-effects (p > 0.05). Conclusion: KAA supplementation along with conservative management is efficacious and safe in preventing the progression of disease in patients of CKD. These findings apply to compound ketoanalogue formulations (of which α-KIC is one component) at doses used in CKD dietary management.

9.6 Oxidative Stress Considerations

Alpha-ketoisocaproic acid and leucine provoke mitochondrial bioenergetic dysfunction in rat brain. Alpha-keto acids accumulating in maple syrup urine disease stimulate lipid peroxidation and reduce antioxidant defences in cerebral cortex from young rats. These effects are documented in the pathological context of MSUD and in animal brain tissue, and their relevance to supplementation-level exposure in healthy humans has not been established.

10. Limitations of the Current Evidence Base

Across all areas of use, several critical limitations apply to the evidence for α-KIC as a dietary supplement ingredient:

Isolation problem: The majority of human studies delivering α-KIC have done so as part of multi-component formulations (GAKIC, compound ketoanalogue tablets, HMB/KIC). Attributing observed effects to α-KIC specifically is not possible in most cases.
Small sample sizes: Most human intervention studies had between 6 and 13 participants, making conclusions highly provisional.
Predominantly animal and in vitro mechanistic data: Key mechanistic claims—particularly regarding mTORC1 activation, protein synthesis stimulation, and cytotoxicity—derive from animal models (neonatal pigs, rats) or cell cultures. Extrapolation to humans at supplemental doses is uncertain.
Training status interactions: GAKIC studies consistently suggest effects may differ between untrained and trained individuals, with trained individuals appearing not to benefit.
Concentration dependency: The compound exhibits qualitatively different effects at physiological vs. supraphysiological concentrations, complicating dose-response interpretation.
Scientific investigations into KIC have included animal studies and human clinical trials, though the body of evidence remains limited.

References

Health Conditions

Health conditions that Alpha-ketoisocaproic acid may help support.

No conditions available.

Body Systems

Body systems that Alpha-ketoisocaproic acid may help support.

No body systems available.