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Citrulline Explained: A Necessary Pre-Workout?

April 24, 2019

Citrulline (or L-Citrulline) is an amino acid that plays a key role in the optimization of blood flow to tissues (including skeletal muscles). It is often sold as a dietary supplement in the form of Citrulline Malate (CM)for dietary purposes (a combination of a salt malate and the amino acid Citrulline). Its name comes from citrillus, the Latin name for watermelon, a natural source of Citrulline. We love watermelon, and we love Citrulline. Other natural sources include peanuts, soybeans and kidney beans.[1] CM is increasingly becoming a topic of discussion amongst athletes and weightlifters due to the many positive benefits shown with its supplementation.

Potential benefits of Citrulline supplementation

  • Increase Muscular and Aerobic Endurance
  • Promote Recovery and Hypertrophy
  • Improve Vasodilation and THE PUMP
  • Prevent Lactic Acid Build Up

How it works

As a supplement, CM affects the body in multiple ways beneficial for physical exercise.


Citrulline -> Arginine -> Nitric Oxide -> Increased Blood Flow Optimization of blood flow is especially important for weightlifters as blood delivers both oxygen and nutrients to skeletal muscle. Increases in blood flow may allow faster recovery times, efficient muscle building (hypertrophy), and greater muscular and aerobic endurance. CM has been shown to assist in vasodilation, which is a relaxing or opening of the blood vessels allowing more blood flow. It does this by increasing nitric oxide levels in the body. Nitric oxide (NO) plays an important role in many bodily functions including regulating vasodilation and blood flow.[2] For this reason, EMTs and Paramedics will often spray nitroglycerin, which supplements NO in the bloodstream, to patience suffering from heart attacks and chest pains associated with heart failures because the NO allows the blood to flow easier. For this same reason, supplements that increase NO in the blood stream also help weightlifters feel "the pump" through increased blood flow to the muscles.

Increased NO through Arginine

Citrulline is a precursor to NO, meaning that its presence in the body can be used to create higher levels of NO in the blood stream. It does this is through arginine, another amino acid and popular sports nutrition supplement. Arginine is the main precursor of NO, meaning that your body can synthesize NO by breaking down arginine. [2] Citrulline is unique because it can be converted into arginine and has been shown in some studies to be a more efficient way to raise arginine levels than arginine supplementation [2]. This means, for all intensive purposes, that supplementation of CM may help endurance, recovery and hypertrophy. Those much-needed nutrients (proteins, carbohydrates, etc.) are more readily available for your taxed muscles. Increased oxygenation of muscles allows them to work more efficiently for greater periods of time.

Increased rate of oxidative ATP production

Another way that CM may help increase cardiovascular and muscular endurance is through oxidative ATP synthesis. In a French study featured in the British Journal of Sports Medicine, ingestion of CM showed a significant increase in the rate of oxidative ATP production during exercise and a faster rate of phosphocreatine recovery after exercise. In layman’s terms, there was a larger amount of energy (ATP) available during aerobic exercise and a faster rate of recovery for the test subjects.[3]

Prevention of Lactic Acid Build Up (Urea Cycle)

CM may also help prevent fatigue by reducing the amount of lactic acid and ammonia build-up caused by exhaustive exercise. Increased Citrulline levels through supplementation have shown in studies to assist in lactate metabolism while malate accelerates the flushing of ammonia.[4] Therefore, fatigue is delayed and reduced. However, this idea must be taken with a grain of salt. Many websites, blogs and products that CM assists in preventing and flushing lactic acid. These claims are widely based on one scientific study performed on mice.[4] While these findings support fatigue reducing results that people experience with Citrulline Malate supplementation, there is much more exhaustive research available on the NO precursor properties of CM than its affects on the urea cycle.

How to use/dosage

In conjunction with weight lifting and working out, most recommendations are for 2-4g before a workout or before and after a workout. Due to low amounts of studies, there is no universally agreed upon dosage. Therefore, double-check the labels on all supplements for dosages and timing as CM is often provided in blends or matrixes with other ingredients.

Potential side effects

Don’t take with kidney abnormalities or problems. As with all supplementation, we recommend speaking with a health care provider before any program is started.


For those who crave "the pump", Citrulline may be a solid supplement to tryout. Its fatigue reducing, recovery accelerating, and muscle building effects make it a stellar ingredient to look for in a pre-workout product. Is CM supplementation necessary for all people looking to make strength gains and grow lean muscle? Nope! It's a supplement and should be treated as such.


  1. Dratta L (2011). “Natural Sources of L-Citrulline”. Retrieved from:
  2. Pons A, Sureda A (2012). “Arginine and citrulline supplementation in sports and exercise: ergogenic nutrients?”. Med Sport Sci. 2013;59:18-28. doi: 10.1159/000341937. PMID: 23075551.
  3. Bendahan D, Mattei JP, Ghattas B, Confort-Gouny S, Le Guern ME, Cozzone PJ (Aug 2002). "Citrulline/malate promotes aerobic energy production in human exercising muscle". Br J Sports Med 36 (4): 282–9. doi:10.1136/bjsm.36.4.282. PMC 1724533. PMID 12145119.
  4. Kohara A, Machida M, Omi N, Takeda K, Takemasa T (2011) Effects of citrulline supplementation on fatigue and exercise performance in mice”. J Nutr Sci Vitaminol (Tokyo). 2011;57(3):246-50. PMID: 21908948.

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