Amino acids are typically associated with building proteins, yet L-citrulline—despite being an amino acid—has little to do with protein synthesis. However, it more than compensates for this apparent shortcoming, as many athletes who use it for supplementation can attest. While L-citrulline won't directly help build muscle mass, it provides invaluable support during every training session.
What Is L-Citrulline?
L-citrulline is a chemical compound that serves as a direct product of ornithine metabolism. Although it doesn't participate in protein synthesis, this amino acid plays a crucial role in the urea cycle—one of the body's most important metabolic pathways. L-citrulline influences the neutralisation of ammonia released during the metabolism of other amino acids, which is why it's classified as an anti-catabolic substance.
This amino acid occurs naturally in the body, but external supplementation becomes advisable during periods of increased physical exertion. This is particularly relevant because L-citrulline isn't commonly found in everyday foods—its main dietary source is watermelon, which rarely features in most people's daily diets. Additionally, watermelons are seasonal fruits, making year-round availability challenging.
[tip:The name "citrulline" comes from Citrullus, the Latin word for watermelon. You'd need to eat several kilograms of watermelon daily to match the citrulline content in a typical supplement dose.]
How L-Citrulline Works
L-citrulline acts as a powerful anti-catabolic agent—a compound that prevents muscle tissue breakdown resulting from either energy deficit or fat reduction phases. This amino acid helps protect muscles during any diet aimed at burning body fat, making it an essential tool for those pursuing body recomposition goals.
Another key property of L-citrulline is improved performance capacity. Research has demonstrated that externally supplemented citrulline noticeably enhances exercise capabilities, including both strength endurance and aerobic capacity. An additional benefit is reduced fatigue perception, which directly enables longer training sessions within a single workout. However, L-citrulline's benefits extend beyond the workout itself—it also supports recovery afterwards by helping to reduce the muscle soreness commonly known as DOMS (delayed onset muscle soreness).
Acid-Base Balance Support
L-citrulline also influences the body's acid-base balance. Citrulline malate, when taken regularly, affects various processes in the body, including the renal reabsorption of bicarbonates. Improved acid-base balance leads to far-reaching benefits: enhanced performance, reduced fatigue, decreased excretion of important minerals, and diminished muscle catabolism.
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L-Citrulline During Fat Loss Phases
According to research, citrulline has a direct impact on anabolic-anticatabolic reactions by activating an important factor for protein synthesis—the threonine-serine protein kinase known as mTOR. While it doesn't stimulate this pathway as strongly as some other supplements, its presence is nonetheless significant.
Moreover, citrulline proves exceptionally useful under conditions of energy and building block deficiencies. Animal studies have shown that increased intake of this amino acid reduces the intensity of muscle tissue breakdown during energy deficit. Human trials have demonstrated similar protective effects during protein restriction. This means citrulline is an excellent supplement for those undergoing fat reduction who want to avoid significant muscle tissue losses—a common concern for anyone in a caloric deficit.
[note:Citrulline malate is the most popular supplemental form, combining L-citrulline with malic acid. This combination may offer additional benefits for energy production through its involvement in the Krebs cycle.]
Citrulline with AAKG: The Nitric Oxide Boosters
Supplements combining citrulline with AAKG (Arginine Alpha-Ketoglutarate) pair citrulline with L-arginine in its highly bioavailable form. Both substances are often called "nitric oxide boosters" because they contribute to increased muscle pump and improved performance during exercise.
Arginine participates in nitric oxide synthesis and metabolic processes, enhancing the transport of nutrients to muscle tissues and thereby improving their efficiency. Citrulline, meanwhile, supports blood flow to tissues, facilitating their nourishment. These combined products are typically taken before training and are suitable for both professional athletes and recreational fitness enthusiasts looking to maximise their sports and fitness results.
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L-Citrulline Dosage Guidelines
L-citrulline supplementation typically uses citrulline malate as the preferred form. The daily dose should range between 2-6 grams, ideally divided into two smaller portions: one taken in the morning and another in the evening or directly before training.
The amount can be gradually increased if the body responds well. Ultimately, doses of up to 10 grams per day can be taken without health risks or adverse effects. For pre-workout use specifically, taking 6-8 grams approximately 30-60 minutes before exercise tends to produce the most noticeable effects on performance and pump.
[warning:While L-citrulline is generally well-tolerated, those with kidney conditions or taking medications affecting blood pressure should consult a healthcare professional before supplementation. Start with lower doses to assess individual tolerance.]
L-Citrulline vs L-Arginine: Which to Choose?
Both amino acids deliver what's known in sports as the muscle pump effect—increased blood flow to muscle tissue, filling it with blood and thereby directly increasing muscle volume. This is why many athletes struggle to choose between them.
A helpful distinction: L-arginine, beyond nitric oxide synthesis, also contributes to the formation of new protein structures, and its use carries numerous health benefits for the body. On the other hand, L-citrulline is more conducive to recovery and urea removal from the body, enabling longer training sessions.
Most importantly, L-citrulline is considered a very safe product, and its dosage can be increased over time to achieve progressively better results. From a health perspective, L-citrulline is the preferred choice for those concerned about safety when taking external amino acid preparations. Interestingly, supplementing with citrulline actually raises arginine levels more effectively than taking arginine directly, as citrulline bypasses liver metabolism and converts to arginine in the kidneys.
Who Should Consider L-Citrulline?
L-citrulline supplementation is particularly beneficial for:
- Endurance athletes seeking improved aerobic capacity and delayed fatigue
- Strength trainers wanting enhanced muscle pump and workout performance
- Those in fat loss phases who want to preserve muscle mass during caloric restriction
- Recreational exercisers looking to improve recovery and reduce post-workout soreness
- Anyone seeking cardiovascular support through improved blood flow and circulation
For comprehensive training support, consider combining citrulline with other performance-focused supplements from our energy support collection. The synergistic effects can help you train harder, recover faster, and achieve your fitness goals more efficiently.
Key Takeaway: L-citrulline is a versatile amino acid that supports training performance, muscle preservation during fat loss, and post-workout recovery. Its excellent safety profile and ability to be increased gradually make it an ideal choice for athletes at all levels seeking to optimise their supplementation strategy.
