Citrulline – What is it and How Can it Enhance Your Performance?



There are so many discussions lately as to how one can naturally boost their health and overall wellbeing with athletic performance in mind. And although most athletes may use things well beyond natural supplements it is worth to explore how simple supps can improve our wellness and fitness. They are cheap, have no side effects and most of all, they are safe and legal. Citrulline and its varieties (such as l-citrulline or citrulline malate, which are just modified structures of the particle) have been on the fore recently. Let’s take a closer look at what it is and why you should even consider getting some.

The Basics

Citrulline is an organic compound found in most pre – workouts. It’s is a non-essential amino acid, which means your body produces it and you don’t have to include it in your diet. As you will soon find out though, it doesn’t mean that you shouldn’t supplement your diet with it. But first things first. Citrulline’s name comes from ‘citrullus’, the Latin word for watermelon, from which it was first isolated in 1914 by Koga & Odake. It acts as a key intermediate in the urea cycle, the pathway by which mammals excrete ammonia. In the body, citrulline is produced as a byproduct of the enzymatic production of nitric oxide from the amino acid arginine, catalyzed by nitric oxide synthase. Simply speaking, our kidneys change citrulline into another amino acid – arginine and a chemical called nitric oxide (a gas, produced by the body, which widens blood vessels and improves blood flow).


Benefits of Citrulline: What does it do?

In simple terms, citrulline improves blood flow and circulation throughout the body. It can benefit both your health and athletic performance, in many ways. The natural, and most beneficial state our body can possibly be in in called homeostasis.


  1. Health Benefits of Citrulline

By boosting the production of nitric oxide in our system, citrulline plays an important role in helping your arteries relax and work better, which improves blood flow throughout your body. This can be helpful for treating or preventing many diseases.

Existing research suggests that supplementing with citrulline can help lower blood pressure in subjects with early signs of hypertension (high blood pressure) which in turn leads to serious cardiac issues.

Another common condition treated successfully with citrulline is ED (erectile dysfunction). While scientists admit that citrulline is not as effective as ED drugs such as Viagra, they agree that it’s a safe and viable option.

Animal studies show citrulline might also help diabetics with wound healing issues by promoting blood vessel health and combating poor circulation. It is also suggested that supplementing with citrulline may help intestinal problems such as celiac disease or short bowel syndrome.

In their study, published in the early 2000s, Meneguello with colleagues brought to the table a discussion on rats, and how supplementation with citrulline affects their general performance and, interestingly, metabolism. The body – rat or human – produces a larger quantity of ammonia during intense exercise. This accumulation can lead to muscle fatigue and drop in efficiency. In order to prevent this process, the urea cycle in the liver eliminates ammonia in the form of urea. The results indicate that citrulline and arginine supplementation in exercising rats increased the glutamine production and the ammonia buffering efficiency.

Animal studies – you may think- are highly inconclusive when it comes to actual human use. Perhaps, but early human studies also show that citrulline may be helpful for Parkinson’s disease, certain dementias and improving protein synthesis in the elderly, preventing them from developing muscle atrophy and malnourishment.

Impressive, right? But what about using citrulline as a sport supplement in humans?


  1. Citrulline and Athletic Performance

Some people also take citrulline to build muscles and improve athletic performance. Rightly so, because studies show that it is more effective than arginine in dilating the blood vessels, creating the ever-desired pump and enhancing the oxygen and nutrient flow to the muscle cells. In one study, resistance-trained men, supplementing with 8 grams of citrulline before their chest workouts increased the number of reps they could do by 52%. It also significantly decreased post- workout muscle soreness.

In another test, 6 grams of citrulline per day increased cellular energy production (ATP) during exercise by 34%, which increases your capacity for physical output and intensity.

According to a study by Pérez-Guisado and Jakeman citrulline malate enhances athletic anaerobic performance and relieves muscle soreness and fatigue. According to Pérez-Guisado and Jakeman:

The purpose of the present study was to determine the effects of a single dose of citrulline malate (CM) on the performance of flat barbell bench presses as an anaerobic exercise and in terms of decreasing muscle soreness after exercise. Forty-one men performed 2 consecutive pectoral training session protocols (16 sets). The study was performed as a randomized, double-blind, 2-period crossover design. Eight grams of CM was used in 1 of the 2 training sessions, and a placebo was used in the other. The subjects’ resistance was tested using the repetitions to fatigue test, at 80% of their predetermined 1 repetition maximum (RM), in the 8 sets of flat barbell bench presses during the pectoral training session (S1-4 and S1′-4′). The p-value was 0.05. The number of repetitions showed a significant increase from placebo treatment to CM treatment from the third set evaluated (p <0.0001). This increase was positively correlated with the number of sets, achieving 52.92% more repetitions and the 100% of response in the last set (S4′). A significant decrease of 40% in muscle soreness at 24 hours and 48 hours after the pectoral training session and a higher percentage response than 90% was achieved with CM supplementation. The only side effect reported was a feeling of stomach discomfort in 14.63% of the subjects. We conclude that the use of CM might be useful to increase athletic performance in high-intensity anaerobic exercises with short rest times and to relieve postexercise muscle soreness. Thus, athletes undergoing intensive preparation involving a high level of training or in competitive events might profit from CM.

Still skeptical? Yes, many studies are conducted on relatively small samples of subjects and other essential factors such as their diet aren’t taken into account which puts the outcome under scrutiny. But still, the confirmed medical evidence that citrulline has health promoting potential also proves that it can impact our fitness. The better your health, the better an athlete you can become.

To summarize – the main benefit of citrulline supplementation for athletes (both professional and amateur) is that it helps our bodies reach homeostasis – the biological balance disturbed by intense activity (caused by chemicals – byproducts in the body of the stress such as ammonia, cortisol etc). Plainly speaking, it helps us get back to top form pretty fast. The decrease of recovery time may help prevent overtraining in people who train regularly.


How to take it

The supplement usually comes in powder form. The suggested dosage for citrulline depends on what disease you are trying to treat or prevent, but is sometimes used up to 10 grams daily, divided throughout the day. However, optimal doses of citrulline have not been set for any condition. Quality and active ingredients in supplements may vary widely. Remember to always purchase your supplements from legitimate sources.

Citrulline Reduces Free Radical Damage

Free radicals are atoms or groups of atoms that can, through chemical reactions, cause damage to cells in the body. They are produced as a result of emotional and physical stress (including exercise).

While free radicals play a vital role in certain basic physiological processes necessary for life, excessive amounts have been associated with aging, and age-dependent diseases such as cardiovascular disease, cancer, neurodegenerative disorders, and other chronic conditions.

Studies show that L-citrulline helps your body better deal with the exercise-induced boost of free radical production by priming immune cells and reducing the number of free radicals produced during workouts.

But what about the other popular nitric oxide booster – arginine? The issue with arginine is, that it’s subject to a more complex path of digestion, going through absorption in the small intestine and liver before being released into general circulation. So, in other words it’s bioavailability it poorer than that of citrulline. Citrulline can go directly into the bloodstream, where it can boost nitric-oxide production. The irony is that citrulline ends up being a better booster of blood arginine levels than arginine—and without arginine’s side effects, which can include fairly intense digestive distress for some people.


It’s safe. It’s natural. It probably works. Citrulline is definitely worth giving a try with the risk being none and potential health and fitness benefits quite promising. Once again, before ingesting any supps, talk to your physician and make sure you buy a licensed, legit product.


Suzuki, T., Morita, M., Kobayashi, Y., & Kamimura, A. (2016). Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men: Double-blind randomized placebo-controlled 2-way crossover study. Journal of the International Society of Sports Nutrition, 13(1), 1.

Bailey, S. J., Blackwell, J. R., Lord, T., Vanhatalo, A., Winyard, P. G., & Jones, A. M. (2015). L-citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans. Journal of Applied Physiology, 119(4), 385-395.

McKinley-Barnard, S., Andre, T., Morita, M., & Willoughby, D. S. (2015). Combined L-citrulline and glutathione supplementation increases the concentration of markers indicative of nitric oxide synthesis. Journal of the International Society of Sports Nutrition, 12(1), 1-8.

Hickner, R. C., Tanner, C. J., Evans, C. A., Clark, P. D., Haddock, A., Fortune, C., … & Mccammon, M. (2006). L-citrulline reduces time to exhaustion and insulin response to a graded exercise test. Medicine and Science in Sports and Exercise, 38(4), 660-666.

Glenn, J. M., Gray, M., Jensen, A., Stone, M. S., & Vincenzo, J. L. (2016). Acute citrulline- malate supplementation improves maximal strength and anaerobic power in female, masters athletes tennis players. European Journal of Sport Science, 1-9.

Wax, B., Kavazis, A. N., Weldon, K., & Sperlak, J. (2015). Effects of supplemental citrulline malate ingestion during repeated bouts of lower-body exercise.

Meneguello, M. O., Mendonca, J. R., Lancha Jr, A. H., &Costa Rosa, L. F. B. P. (2003). Effect of arginine, ornithine and citrulline supplementation upon performance and metabolism of trained rats.

Pérez-Guisado, J. &Jakeman, P. M. (2010) Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness.

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