L-Citrulline DL-Malate
Mechanism of Action +
### The Urea Cycle and Ammonia Clearance L-Citrulline is a non-essential alpha-amino acid that plays a central role in the urea cycle, a metabolic pathway primarily occurring in the liver and kidneys designed to excrete highly toxic ammonia from the body. During intense physical exertion, the breakdown of amino acids and the accumulation of metabolic byproducts lead to elevated ammonia levels in the blood and muscle tissue. High ammonia concentrations induce muscular fatigue and interfere with energy metabolism. By supplementing with L-Citrulline, the body's capacity to process and eliminate ammonia via the urea cycle is enhanced, thereby delaying the onset of fatigue during strenuous exercise.
### The Nitric Oxide (NO) Pathway and Vasodilation Unlike L-arginine, which is subject to extensive first-pass metabolism by the enzyme arginase in the liver and intestines, L-citrulline easily bypasses hepatic breakdown. Once absorbed into the bloodstream, it is transported to the kidneys, where it is converted into L-arginine by the enzymes argininosuccinate synthase and argininosuccinate lyase. This renal conversion results in a more sustained and significant elevation of plasma arginine levels than supplementing with L-arginine directly.
The newly synthesized L-arginine is then utilized by endothelial nitric oxide synthase (eNOS) to produce nitric oxide (NO) in the endothelial cells lining the blood vessels. Nitric oxide is a potent signaling molecule that diffuses into the adjacent smooth muscle cells, activating soluble guanylyl cyclase (sGC). This activation increases the production of cyclic guanosine monophosphate (cGMP), which leads to the relaxation of smooth muscle fibers. The resulting vasodilation widens the blood vessels, reducing blood pressure and significantly increasing blood flow, oxygen delivery, and nutrient transport to working skeletal muscles.
### The Role of DL-Malate in Energy Production Citrulline Malate is distinguished from pure L-Citrulline by the addition of DL-malate (malic acid). Malate is a key intermediate in the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle or citric acid cycle. The TCA cycle is the primary metabolic pathway for aerobic energy (ATP) production within the mitochondria. By providing exogenous malate, the supplement supplies an anaplerotic substrate that helps replenish TCA cycle intermediates, potentially increasing the rate of ATP production. Furthermore, malate is involved in the malate-aspartate shuttle, which facilitates the transfer of reducing equivalents into the mitochondria, further supporting oxidative phosphorylation and energy yield. This dual-action mechanism—enhanced blood flow from citrulline and enhanced ATP production from malate—makes Citrulline Malate particularly effective for anaerobic and high-intensity exercise.
What is L-citrulline DL malate good for? +
Is it safe to take L-citrulline malate every day? +
Does L-citrulline lower cholesterol? +
Does L-citrulline lower blood sugar? +
What is the difference between L-citrulline and citrulline malate? +
How much citrulline malate should I take before a workout? +
Does citrulline malate help with erectile dysfunction? +
Can citrulline malate lower blood pressure? +
Why is citrulline better than arginine supplements? +
When is the best time to take citrulline malate? +
Do I need to take citrulline malate with food? +
What does the '2:1' mean in citrulline malate? +
Will citrulline malate keep me awake at night? +
Does citrulline malate reduce muscle soreness? +
Can women take citrulline malate? +
Is citrulline malate a pre-workout? +
What foods contain citrulline naturally? +
Does citrulline malate improve aerobic or anaerobic exercise? +
Everything About L-Citrulline DL-Malate Article
## What is L-Citrulline DL-Malate?
L-Citrulline DL-Malate is one of the most popular and scientifically validated ingredients in the sports nutrition industry. It is a compound consisting of the non-essential amino acid L-citrulline bound to malic acid (DL-malate). Originally discovered in watermelon (the Latin word for watermelon is *Citrullus*), citrulline is produced naturally by the human body in the liver and intestines.
Unlike other amino acids, citrulline is not used to build structural proteins. Instead, it plays a critical role in the urea cycle—a system that removes toxic ammonia from the body—and serves as a highly efficient precursor to L-arginine and nitric oxide (NO). When combined with malic acid, an intermediate in the Krebs cycle, Citrulline Malate becomes a dual-threat supplement: it enhances blood flow and nutrient delivery while simultaneously supporting cellular energy production.
## The Science of Nitric Oxide and Vasodilation
To understand why Citrulline Malate is so effective, you must understand the nitric oxide pathway. For years, supplement manufacturers sold L-arginine with the promise of boosting nitric oxide. However, oral L-arginine is highly susceptible to first-pass metabolism. When you consume L-arginine, the enzyme arginase in the intestines and liver breaks down a massive portion of it before it ever reaches the bloodstream.
L-Citrulline completely bypasses this hepatic breakdown. It enters the bloodstream intact and travels to the kidneys, where it is readily converted into L-arginine. Research consistently shows that supplementing with L-citrulline raises blood plasma levels of arginine significantly higher and for a longer duration than supplementing with L-arginine itself.
Once converted, this arginine is used by endothelial cells (the cells lining your blood vessels) to produce nitric oxide. Nitric oxide acts as a signaling molecule that tells the smooth muscle tissue around your blood vessels to relax. This process, known as vasodilation, widens the blood vessels. For athletes, vasodilation means a massive increase in blood flow to working muscles, delivering more oxygen and nutrients while creating the highly sought-after muscle "pump."
## The Role of Malic Acid (DL-Malate)
While pure L-Citrulline is excellent for cardiovascular health and blood flow, the addition of malic acid makes Citrulline Malate the superior choice for athletic performance. Malate is a key component of the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle. This cycle is the primary way your cells generate ATP (adenosine triphosphate), the energy currency of the body.
During intense exercise, the demand for ATP skyrockets. By providing exogenous malate, Citrulline Malate helps replenish the intermediates of the Krebs cycle, allowing for sustained energy production. Furthermore, malate helps clear lactic acid, delaying the burning sensation that forces you to drop the weight.
## Athletic Performance Benefits
The clinical evidence supporting Citrulline Malate for sports performance is robust. According to Examine.com, citrulline is backed by over 46 trials and 5 meta-analyses involving thousands of participants.
### Increased Repetitions and Anaerobic Capacity One of the most famous studies on Citrulline Malate, highlighted by WebMD, involved men performing weight training. The participants who consumed 8,000mg of Citrulline Malate prior to their workout were able to perform 53% more repetitions to failure compared to the placebo group. This massive increase in training volume is the primary reason Citrulline Malate is a staple in modern pre-workout formulations.
### Reduced Muscle Soreness (DOMS) In the same weight training study, the participants who took Citrulline Malate reported a significant reduction in delayed onset muscle soreness (DOMS) 48 hours after the workout. By improving blood flow and clearing metabolic waste products like ammonia and lactate, citrulline helps the body recover faster between sessions.
### Aerobic Endurance While citrulline is most famous for weightlifting, it also benefits endurance athletes. The Cleveland Clinic notes a study involving avid cyclists who took 2.4 grams of L-citrulline daily for eight days. The supplemented group biked faster and reported feeling significantly less fatigued after a 4-kilometer time trial. Citrulline improves the efficiency of oxygen utilization in muscle tissue, allowing endurance athletes to maintain higher outputs for longer periods.
## Cardiovascular and Men's Health Benefits
Beyond the gym, the vasodilatory effects of citrulline have profound implications for general health.
### Blood Pressure Management Examine.com awards Citrulline a Grade B (Moderate confidence) for improving blood pressure. By increasing nitric oxide and relaxing blood vessels, citrulline reduces the resistance against which the heart must pump. Studies have shown moderate improvements in blood pressure, particularly in individuals with hypertension or heart failure.
### Erectile Dysfunction Erectile function is heavily dependent on blood flow and nitric oxide signaling. Because L-citrulline effectively boosts NO production, it is often used as a natural intervention for mild erectile dysfunction. According to WebMD, one study showed that half of the men taking an L-citrulline supplement experienced an 8.3% improvement in their erectile dysfunction scores compared to a placebo.
## Dosing Strategies: How Much Should You Take?
Dosing citrulline correctly is critical, as it is one of the most commonly underdosed ingredients in the supplement industry.
### For Sports Performance To achieve the performance benefits seen in clinical trials (increased reps, reduced soreness), the clinical standard dose is **6,000mg to 8,000mg of Citrulline Malate**, taken approximately 45 to 60 minutes before exercise.
It is important to understand the conversion ratio. Citrulline Malate is typically sold in a 2:1 ratio (two parts citrulline to one part malic acid). To get the equivalent of 1 gram of pure L-citrulline, you need to consume 1.76 grams of Citrulline Malate. Therefore, an 8-gram dose of Citrulline Malate 2:1 yields roughly 5.3 grams of active L-citrulline, which is the optimal sweet spot for performance.
### For Cardiovascular Health and ED If you are taking citrulline purely for circulatory health, blood pressure, or erectile dysfunction, pure L-Citrulline is often preferred. The recommended protocol is 2,000mg of L-Citrulline taken three times a day (for a total of 6,000mg daily). This can be taken with or without food, though taking it with meals is often suggested for circulatory protocols.
## Safety and Side Effects
Citrulline is incredibly safe and well-tolerated. Because it is an amino acid naturally produced by the body and found in foods like watermelon, it does not carry the risks associated with stimulants. There is no known upper tolerable limit, and side effects are exceedingly rare.
However, because citrulline lowers blood pressure via vasodilation, it should not be combined with prescription erectile dysfunction medications (PDE5 inhibitors like Viagra or Cialis) or severe blood pressure medications without consulting a doctor, as the combination could cause an unsafe drop in blood pressure.
## The Bottom Line
L-Citrulline DL-Malate is a foundational supplement for anyone serious about their physical performance. Whether you are a bodybuilder chasing skin-tearing pumps, a powerlifter looking for extra repetitions, or a cyclist trying to shave seconds off your time trial, the clinical evidence supports the use of 6-8 grams of Citrulline Malate pre-workout. It is safe, highly effective, and remains the gold standard for nitric oxide production in sports nutrition.