Leucine malate

Other Names

L-Leucine DL-malateL-Leucine malateL-Leucine malic acid salt

Synopsis

Leucine Malate: A Comprehensive Reference

1. Identity and Chemical Characterization

Leucine malate is a dietary supplement ingredient comprising two distinct molecules: L-leucine, an essential branched-chain amino acid, and malate (the anionic or acid form of malic acid). The term "leucine malate" as used in the supplement industry describes a combination or salt/complex of these two compounds. It is important to understand each constituent independently, as the scientific literature almost exclusively studies them separately, and there are currently no peer-reviewed human clinical trials investigating leucine malate as a distinct, unified chemical entity.

1.1 L-Leucine

Leucine (symbol Leu or L) is an essential amino acid used in the biosynthesis of proteins. It is an α-amino acid, containing an α-amino group, an α-carboxylic acid group, and a side chain isobutyl group, making it a non-polar aliphatic amino acid. Its CAS number is 61-90-5, with synonyms including Leu and NSC 46709. Leucine has the chemical formula HO₂CCH(NH₂)CH₂CH(CH₃)₂.

It is essential in humans and animals, meaning the body cannot synthesize it; it must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, and beans and other legumes.

1.2 Malate (Malic Acid)

Malic acid is an organic compound with the molecular formula HO₂CCH(OH)CH₂CO₂H. It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms (L- and D-enantiomers), though only the L-isomer exists naturally. The salts and esters of malic acid are known as malates, and the malate anion is a metabolic intermediate in the citric acid cycle. L-malic acid is the naturally occurring form of malic acid, found mainly in sour and unripe fruits.

Malic acid was first isolated from apple juice by Carl Wilhelm Scheele in 1785. Antoine Lavoisier in 1787 proposed the name acide malique, which is derived from the Latin word for apple, mālum. L-malic acid is the naturally occurring form, whereas a mixture of L- and D-malic acid is produced synthetically. The DL-malate form (a racemic mixture) is commonly encountered in supplement formulations such as citrulline malate.

1.3 Leucine Malate as a Supplement Form

In the dietary supplement context, "leucine malate" parallels other amino acid-malate combinations (such as citrulline malate) in which an amino acid is combined with malic acid, either as an ionic salt or as a co-formulated mixture. The rationale for the malate component draws on its established role as a Krebs cycle intermediate. The primary rationale for using amino acid–malate combinations is the potential synergistic benefit of malic acid, which is an intermediate in the Krebs cycle (or citric acid cycle), the body's primary energy production pathway. Malic acid, especially in the form of its anion malate, is a key intermediate in the major biochemical energy-producing cycle in cells known as the citric acid or Krebs cycle, located in the cells' mitochondria.

The Food and Drug Administration (FDA) recognizes both L-leucine and malic acid as generally safe food ingredients. Malic acid is a naturally occurring acidulant and low acid food additive, present in most fruits and vegetables, widely used to enhance flavor, adjust pH, and control bacterial growth. No standalone regulatory or pharmacopeial monograph specific to "leucine malate" as a combined entity has been identified in the publicly available literature from government or institutional health bodies at the time of writing.

2. Natural Sources

L-leucine is essential in humans and must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, and beans and other legumes.

Malic acid is a naturally occurring compound present in most fruits and vegetables. It is found in particularly high concentrations in apples (from which the name is derived), cherries, grapes, and pears. L-malic acid is an important organic acid produced during the metabolism of organisms, serving as an important intermediate product of the citric acid (TCA) cycle and its branch glyoxylate metabolic processes.

3. Common Forms and Preparations

Leucine malate is sold primarily in powdered form, intended for dissolution in water or inclusion in capsules. It is frequently marketed as a pre-workout or sports-recovery ingredient. The compound appears in supplement formulations alongside other branched-chain amino acids (BCAAs), electrolytes, and carbohydrates. Other analogous malate-complexed amino acids in common commercial use include citrulline malate and arginine malate, which follow the same preparation principle of combining a free amino acid with malic acid.

The Food and Nutrition Board (FNB) of the U.S. Institute of Medicine set Recommended Dietary Allowances (RDAs) for essential amino acids in 2002; for leucine, for adults 19 years and older, the RDA is 42 mg/kg body weight per day. In supplement applications, leucine is commonly offered as a free-form powder, as part of BCAA blends, or as enriched protein formulations.

4. Traditional and Historical Use

Leucine as an isolated supplement has no documented history of traditional or ethnobotanical use, as it was not identified as a distinct chemical entity until the early nineteenth century. Leucine was first isolated from muscle fiber and wool in 1820 by the French chemist Henri Braconnot. Malic acid was first isolated in 1785 by Scheele. Neither compound was conceptualized, named, or employed as a dietary supplement in any pre-modern medicinal tradition.

Traditional dietary practices in many cultures incorporated leucine and malate-rich foods implicitly as part of protein- and fruit-rich diets, but no historical record attributes specific therapeutic intent to these individual compounds in isolation. The concept of amino acid supplementation emerged in the late twentieth century with advances in nutritional biochemistry. The deliberate combination of an amino acid with a Krebs cycle organic acid in supplement form is a modern formulation strategy, analogous to the development of citrulline malate for treating asthenia, which was originally developed for treating asthenia (abnormal physical weakness and lack of energy). Leucine malate as a discrete supplement category likewise has no pre-twentieth-century history of use.

5. Key Constituents and Established Mechanisms of Action

5.1 Leucine: Mechanisms

mTOR Pathway Activation and Protein Synthesis

The effects of leucine on protein synthesis are brought about, at least in part, by activation of a cell-signaling pathway involving the mammalian target of rapamycin (mTOR), a serine/threonine protein kinase. Leucine and insulin appear to activate independent intracellular signaling pathways which converge at mTOR and eventually affect translation initiation and elongation. Ingestion of a leucine-enriched essential amino acid nutrient solution rapidly and potently activates the mTOR signaling pathway and protein synthesis in human skeletal muscle.

The branched-chain amino acid leucine can activate the translational regulators PHAS-I and p70 S6 kinase (p70s6k), in an insulin-independent and rapamycin-sensitive manner through mTOR, although the mechanism for this activation is not fully defined. L-leucine activates the transducer of regulated cAMP response element-binding protein activity 1 (TORC1) in human skeletal muscle; the activation of TORC1 contributes to the initial stimulus of muscle protein synthesis, increasing the availability of amino acids through translation.

Insulin Secretion

Leucine is one of the most potent insulin secretagogues among the branched-chain amino acids, facilitating glucose-induced insulin release from pancreatic β-cells. Leucine can either serve as a fuel source for ATP production or be converted to α-ketoisocaproate, a metabolic intermediate that inhibits K_ATP channel activity, leading to membrane depolarization and triggering insulin secretion. Leucine also regulates insulin release by acting on glutamate dehydrogenase (GDH), a key enzyme that fuels amino acids into the tricarboxylic acid cycle.

Suppression of Muscle Protein Breakdown

Among essential amino acids (EAAs), leucine is the most potent stimulator of muscle protein synthesis due to its capacity to activate the mTOR pathway and suppress proteasomal degradation. As a dietary supplement, leucine has been found to slow the degradation of muscle tissue by increasing the synthesis of muscle proteins in aged rats.

Energy and Lipid Metabolism

Leucine has a strong effect on energy and lipid metabolism. Increased energy expenditure and toxic lipids removal by increasing the prevalence and activity of leucine may be a promising therapeutic strategy to treat obesity and its consequent conditions.

5.2 Malate: Mechanisms

Malic acid is not only a Krebs cycle intermediate metabolite, but it is also part of the malate-aspartate shuttle, playing an important role in regulating aerobic metabolism. Malic acid acts as a catalyst in the Krebs cycle to increase energy production from the burning of pyruvic acid. By directly participating in mitochondrial oxidative phosphorylation, malate theoretically supports adenosine triphosphate (ATP) synthesis. Malic acid supplements can promote substrates and regulate the level of energy metabolism, improve cardiac function, alleviate sports fatigue, and promote regeneration.

6. Scientific Evidence by Area of Use

Note: No peer-reviewed human clinical trials on "leucine malate" as a unified compound were identified in the literature. The following sections present the evidence for L-leucine and malate separately, as this is how the science is conducted and published. Claims about their combined use in leucine malate are therefore extrapolated from constituent research and must be interpreted as preliminary at best.

6.1 Skeletal Muscle Protein Synthesis

Evidence strength: Moderate for L-leucine; absent specifically for leucine malate.

Leucine supplementation during feeding improves muscle protein synthesis in the elderly independently of an overall increase of other amino acids. A key human study enrolling twenty normal elderly men examined the isolated effect of leucine on fractional synthetic rate using stable isotope tracer methodology. This effect was due only to increased leucine availability, because only plasma free leucine concentration significantly differed between the control and leucine-supplemented groups; the conclusion was that leucine supplementation during feeding improves muscle protein synthesis in the elderly independently of an overall increase of other amino acids.

A study published in the American Journal of Physiology–Endocrinology and Metabolism used stable isotope tracer methods to study eight male subjects across three crossover conditions. Subjects consumed drinks containing either carbohydrate (CHO), carbohydrate and protein (CHO+PRO), or carbohydrate, protein, and free leucine (CHO+PRO+Leu) following 45 minutes of resistance exercise, with fractional synthetic rate (FSR) in the vastus lateralis muscle assessed during 6 hours of postexercise recovery. Plasma insulin response was higher in the CHO+PRO+Leu condition compared with both CHO and CHO+PRO trials.

mTOR signaling and muscle protein synthesis are enhanced when leucine-enriched nutrients are ingested following resistance exercise. The addition of leucine to regular meals may improve the ability of feeding to stimulate protein synthesis in old human muscle.

In an endurance context, a 2025 randomized controlled trial in cross-country skiers showed that twenty skiers were randomized into placebo and leucine groups, with subjects given leucine (8.5 g) plus sucrose (14 g) or only sucrose (14 g) supplements twice each day from Monday to Saturday for 6 weeks. After intervention, ankle muscle strength and VO₂max were increased in the leucine group compared to placebo.

6.2 Sarcopenia and Muscle Mass in Older Adults

Evidence strength: Mixed; isolated leucine supplementation shows limited benefit on muscle mass alone, but combination with other nutrients shows promise.

A systematic review and meta-analysis published in Frontiers in Nutrition (2022) identified 17 RCTs enrolling 1,418 subjects. Studies suggested that L-leucine supplementation was able to enhance muscle protein synthesis in the elderly; some RCTs indicated that leucine could improve clinical indicators of sarcopenia, including functional performance and bone mineral-free lean tissue mass. In contrast, several trials reported that prolonged leucine supplementation could not modulate body composition, muscle mass, and strength in elderly individuals.

The pooled quantitative findings of this meta-analysis were telling: leucine-isolated supplementation showed no effect on total lean mass (WMD = 0.03 kg, 95% CI: –0.51, 0.57, P = 0.917), handgrip strength (WMD = 1.23 kg, 95% CI: –0.58, 3.03, P = 0.183), or leg press (WMD = –1.35 kg, 95% CI: –7.46, 4.77, P = 0.666). However, leucine-combined supplementation including vitamin D showed a significant improvement in handgrip strength (WMD = 2.17 kg, 95% CI: 0.24, 4.10, P = 0.027) and gait speed (WMD = 0.03 m/s, 95% CI: 0.01, 0.05, P = 0.008).

A separate meta-analysis of six RCTs in sarcopenic older adults (n = 699) reported that leucine-rich protein supplements improved participants' overall muscle strength, mass, and performance compared to control (SMD = 0.939; 95% CI, 0.440–1.438; P < 0.001). In this meta-analysis, leucine-rich protein was suggested to improve muscle strength, though muscle mass and physical performance tended to improve without reaching significance.

A further meta-analysis involving 999 older individuals found that leucine supplementation significantly increased lean body mass (MD = 0.99 kg, P = 0.0005), body weight (MD = 1.02 kg, P = 0.02), and BMI (MD = 0.33 kg/m², P = 0.001), particularly among participants with sarcopenia. However, no significant effects on muscle strength, such as handgrip or knee extension strength, were observed.

Long-term leucine supplementation does not increase muscle mass or strength in healthy elderly men, underscoring that the benefit may be context-specific, particularly relevant in populations with low dietary protein or established sarcopenia.

6.3 Athletic Performance and Exercise Recovery

Evidence strength: Preliminary for leucine alone; absent for leucine malate specifically.

Dietary supplementation of the leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) at 3 g/day to humans undertaking intensive resistance training exercise resulted in an increased deposition of fat-free mass and an accompanying increase in strength. Muscle proteolysis was also decreased with HMB, accompanied by lower plasma levels of enzymes indicating muscle damage.

BCAA supplementation (76% leucine) in combination with moderate energy restriction has been shown to induce significant and preferential losses of visceral adipose tissue and to allow maintenance of a high level of performance. However, caution must be paid when interpreting the limited number of studies in this area since, in many studies, leucine has been supplemented as part of a mixture of BCAAs; consequently, further research into the effects of leucine supplementation alone is needed.

A 2025 PLOS One study of basketball athletes reported that leucine supplementation resulted in a statistically significant improvement in sprint performance, with times decreasing from 17.4 ± 0.9 to 16.2 ± 0.9 seconds in the leucine group (P = 0.034), suggesting that leucine positively influenced speed and agility, likely by promoting muscle recovery, reducing fatigue, and enhancing muscle protein synthesis through the activation of the mTOR signaling pathway.

Regarding the malate component: evidence suggests that increasing the concentration of leucine in an EAA supplement consumed during steady state exercise elicits a greater muscle protein synthesis (MPS) response during recovery. The malate moiety theoretically contributes via Krebs cycle support. Supplementation of malic acid has been reported to be beneficial in Chronic Fatigue Syndrome by reducing symptoms of persistent fatigue, muscular myalgia, and arthritic-like pains. However, the underlying clinical evidence base for malic acid in exercise or fatigue contexts is sparse and methodologically limited.

6.4 Glycemic Control and Metabolic Health

Evidence strength: Preliminary; primarily animal data.

Dietary branched-chain amino acids or leucine have beneficial effects on glucose metabolism and glycogen synthesis of muscle. Leucine supplementation improves insulin sensitivity in liver and muscle and then influences systemic glucose homeostasis. In mouse models, leucine supplementation significantly reduced HbA1c levels throughout the study period, though the treatment had no long-term effect on body weight or adiposity. The improvement in glycemic control was associated with an increased insulin response to food challenge in one model and decreased plasma insulin levels in another. These are animal data and cannot be directly extrapolated to humans.

6.5 Energy Metabolism and Fatigue (Malate Component)

Evidence strength: Weak; mostly mechanistic and small-scale clinical data.

Some scientific interest has focused on malic acid supplementation for supporting energy levels, particularly in people with chronic fatigue syndrome (CFS) and fibromyalgia, as these conditions are thought to involve impaired energy metabolism. A few small clinical trials have explored the effects of malic acid, usually in combination with magnesium, in patients with fibromyalgia. A 1995 double-blind study (Russell et al.) found that a combination of malic acid and magnesium improved pain and tenderness after 8 weeks, but the improvement was not significant at the earlier time point.

Overall, while the biological rationale for malic acid's role in energy production is strong, actual clinical evidence supporting its use for fatigue or low energy remains limited and inconclusive. The current evidence base rates as weak, and more rigorous studies are needed before recommending malic acid supplementation for energy support.

7. Body Systems and Health Areas of Association

Musculoskeletal System: Some observational studies and randomized controlled trials have reported associations between leucine and muscle mass, muscle properties, and muscle functions.
Endocrine/Metabolic System: In addition to its role as an insulin secretagogue, leucine appears to be a nutrient signal that regulates protein synthesis in adipose as well as other tissues by mechanisms that are independent of insulin.
Mitochondrial/Bioenergetic System: A beneficial effect of leucine on mitochondrial function (energy generation, proteins of the tricarboxylic cycle) has been reported. Malate's role as a Krebs cycle intermediate directly implicates this system.
Cardiovascular System: Leucine improved myocardial diastolic function in an HFpEF (heart failure with preserved ejection fraction) animal model. These findings are preclinical.
Pancreatic Function: Leucine and its metabolite KIC significantly stimulate the phosphorylation of p70S6K and enhance protein synthesis in pancreatic β-cells in a rapamycin-sensitive and insulin-independent manner at physiological concentrations ranging from 0.4 mM to 4 mM.

8. Dosage Forms and Dosages Reported in Studies

The following dosages are reported from specific scientific studies and are presented purely as recorded in those sources.

RDA for leucine: The Food and Nutrition Board set the RDA for leucine for adults aged 19 years and older at 42 mg/kg body weight per day.
Proposed upper limit of safe intake (elderly): The total dietary leucine upper limit of safe intake (ULSI) proposed for elderly individuals is 500 mg · kg⁻¹ · d⁻¹.
Endurance athlete RCT: Twenty cross-country skiers were given leucine (8.5 g) plus sucrose (14 g), or sucrose alone (14 g), twice daily from Monday to Saturday for 6 weeks, for a total leucine dose of 17 g per day.
Post-exercise protein synthesis study: Eight male subjects consumed drinks containing carbohydrate with or without protein and/or free leucine following 45 minutes of resistance exercise, with recovery assessed over 6 hours. Specific leucine amounts were not detailed in the abstract excerpt available.
HMB (leucine metabolite) study: Supplementation of the leucine metabolite HMB at 3 g/day to humans undertaking intensive resistance training exercise resulted in increased fat-free mass and strength.
Hypoglycemia threshold reference: Excessive intake of L-leucine (greater than 750 mg/kg body weight) may result in hypoglycemia. L-leucine when ingested up to 200 mg/kg dose has no effect on plasma insulin or glucose.
Metabolic upper limit study: Five young healthy men received graded stepwise increases in leucine from 50 to 1250 mg/(kg·d) across 7 dosages; the metabolic limit to oxidize leucine and rises in leucine and ammonia plasma concentrations were all observed at intakes greater than 500 mg/(kg·d).

Malic acid, as used in malate supplement contexts, does not have an established standalone supplemental dosage supported by rigorous clinical evidence. In citrulline malate preparations (a model analogous to leucine malate), a 6-gram dose of citrulline malate 2:1 delivers approximately 4 grams of L-citrulline and 2 grams of malic acid.

9. Safety Considerations and Interactions

9.1 General Safety of L-Leucine

The total dietary leucine upper limit of safe intake proposed for elderly individuals is 500 mg · kg⁻¹ · d⁻¹. The metabolic limit to oxidize leucine and the rise in leucine and ammonia plasma concentrations were all observed at intakes greater than 500 mg/(kg·d).

9.2 Hypoglycemia Risk

Excessive intake of L-leucine (greater than 750 mg/kg body weight) may result in hypoglycemia. L-leucine when ingested up to 200 mg/kg dose has no effect on plasma insulin or glucose. This is based on pharmacokinetic and toxicological data from clinical trial documentation.

9.3 Pellagra-Like Symptoms at Very High Doses

While not reported in human beings, animal models suggest that very high doses of L-leucine (in rodent models at 15 g/kg) may lead to pellagra-like symptoms due to disruption of tryptophan metabolism. This is an animal-only finding with no confirmed human equivalent at typical supplement doses.

9.4 Drug Interactions

L-leucine also has a synergistic effect on the action of phosphodiesterase 5 (PDE5) inhibitors and may lead to interaction with medications such as sildenafil.

9.5 Maple Syrup Urine Disease (MSUD)

Maple syrup urine disease (MSUD) is an autosomal recessive metabolic disease resulting in impaired or absent breakdown of branched-chain amino acids valine, isoleucine, and leucine. Classic MSUD is treated with a protein-restricted diet supplemented with medical food to prevent toxic buildup of blood leucine. Leucine supplementation is absolutely contraindicated in individuals with MSUD, as acute episodes of hyperleucinemia in MSUD patients require clinical management to prevent encephalopathy and cerebral edema.

9.6 Leucine-Sensitive Hyperinsulinemic Hypoglycemia

Patients with specific enzyme mutations (such as HADH loss-of-function mutations) demonstrated severe hyperinsulinemic hypoglycemia in response to oral leucine load; this hypoglycemia was not observed in control subjects subjected to the same leucine load. This is a rare genetic condition but represents an important contraindication to leucine supplementation for affected individuals.

9.7 Interactions with Low-Protein Diets

Animal data indicate that except when animals were fed a low-protein diet, leucine intake up to 8% had no adverse effects. This suggests that very high leucine supplementation on a background of inadequate total protein may carry additional risk.

9.8 Safety of Malic Acid

Since malic acid occurs naturally in many foods and is produced by the human body as part of normal metabolism, most people tolerate it well. However, some individuals may experience mild digestive effects when first starting supplementation.

10. Summary of Evidence Strength

Leucine malate as a combined entity: No peer-reviewed clinical trials identified. Evidence for this specific formulation is absent. All claims rest on constituent research.
L-leucine for muscle protein synthesis in elderly/clinical populations: Moderate evidence from multiple RCTs and meta-analyses, with the caveat that isolated leucine supplementation does not robustly improve muscle mass or strength in healthy older adults.
L-leucine for athletic performance: Preliminary; individual RCTs show mixed or modest effects; leucine is frequently studied in BCAA mixtures, complicating isolation of its specific contribution.
Malate for energy metabolism and fatigue: Weak; biological rationale is mechanistically sound, but clinical evidence is sparse, methodologically limited, and largely confined to combination products (e.g., with magnesium) in disease states.
Combined leucine + malate synergy: Theoretical; no human trials have directly compared leucine malate against leucine alone to isolate any additive or synergistic malate contribution.

References

Health Conditions

Health conditions that Leucine malate may help support.

No conditions available.

Body Systems

Body systems that Leucine malate may help support.

No body systems available.