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Citrulline Malate: The Most Mis-Used Weapon in Aerobic and Anaerobic Performance

By Kevin Kuhn: Classified Nutrition

When I first started combining supplement ingredients to make my own “pre-workout recipe,” I was not very familiar with citrulline malate.  I knew it was an added ingredient in a BCAA product I had been using for a while, but a quick pubmed.gov search showed me it wasn’t anywhere near the minimum effective dose, so I paid no real attention to it.

A few years later I was re-introduced to this ingredient in a pre-workout product from a supplement line created by a scientist and athlete I respected very much.  So it seemed it was time to reconsider the science on this ingredient.  What I learned impressed me very much because of the benefit citrulline malate can deliver to nearly every single type of athlete, regardless of the sports’ physical demands.

Studying the new research and data on this ingredient, there was something big that stood out that I believe may be preventing athletes from getting the full benefit of supplementing citrulline malate.  It deals with the dosage and timing of ingestion, which is something that is often vague or lacking on supplement labels.  So in order to get the full benefit, it is important to know how much to ingest, and how long before training you need to ingest it.  To best understand why the dose and time is important, we have to dig into a little biochemistry.

Citrulline is a dietary amino acid that plays a major role in proper circulatory function.  It is also a major intermediary in the urea cycle.  Citrulline works together with Arginine and Ornithine to recycle ammonia and in the effective production of nitric oxide.  The breakdown of amino acids within the body results in ammonia as a byproduct.  Since ammonia is toxic, the body converts the ammonia to urea in the liver, which then travels through the blood to the kidneys where it is filtered out of the body via urine.  The basic process of removing ammonia from the body happens like this:

  • Ammonia is converted to carbamoyl phosphate
  • Carbamoyl phosphate reacts with ornithine, resulting in citrulline
  • Citrulline reacts with aspartate to form argininosuccinate
  • Argininosuccinate is broken down into fumarate and arginine
  • Arginine is broken down to form urea and ornithine
  • Ornithine starts the process over by reacting with carbamoyl phosphate (ammonia)

Since exercise up-regulates amino acid catabolism and therefore the production of ammonia, it is easy to understand the initial rationale behind supplementing with these urea cycle amino acids, specifically arginine.  Since arginine is also converted to nitric oxide, it was thought to be the perfect supplement ingredient.  Nitric oxide is a signaling molecule that quickly results in increased blood flow by vasodilation.  Increasing blood flow, especially during training and competition, means an increase in delivered oxygen and nutrients to working tissue and more efficient removal of metabolic waste.  This is why arginine was, and still is, used as a pre-workout ingredient to “increase muscle pumps.”

supplemental citrulline, compared to supplemental arginine, results in elevated plasma levels of arginine for a longer period of time, without any gastrointestinal issues

“Arginine was, and still is, used as a pre-workout ingredient to ‘increase muscle pumps’.  Unfortunately there were some un-intended side-effects”

The issue with arginine supplementation, researchers discovered, is that the dose needed to increase plasma levels of arginine tends to be very difficult for the intestines to absorb, which results in gastrointestinal distress…also known as diarrhea.  Researchers since have found out that supplemental citrulline, compared to supplemental arginine, results in elevated plasma levels of arginine for a longer period of time, without any gastrointestinal issues.  For general circulatory health, research therefore recommends 1000 mg of L-citrulline taken three times per day, but for improved sports performance, supplementing with 6-8 grams of citrulline malate seems to work the best.

So why not just throw 6-8 grams of citrulline malate into your pre-workout mix, or buy a pre-workout product with that much citrulline malate?  Well, most pre-workout products are designed to be ingested 20-30 minutes before training, or during the warm-up.  Citrulline malate takes about an hour to be converted to arginine and then nitric oxide; so taking it right before training may not deliver significant ergogenic assistance.

Citrulline Malate: The Most Mis-Used Weapon in Aerobic and Anaerobic Performance

To get the full benefit of citrulline malate, you need to take it an hour before you start training.  This means you will probably have to ingest the fully effective dose of citrulline malate about half an hour before you normally consume your pre-workout supplement.  For this reason, I think citrulline malate is an awesome stand-alone product, and not something that you will get the most benefit from if it is pre-combined with other pre-workout ingredients.  If you are looking to increase your training volume by delaying fatigue, reducing muscle soreness, increasing growth hormone production, boosting immune function, and improving aerobic and anaerobic endurance, then taking the time to properly schedule your citrulline malate ingestion before your other pre-workout ingredients is well worth the effort and planning.

Like every other “effective” supplement ingredient, you have to know the effective dose as well as the effective timing of ingestion.  Citrulline malate can be a very useful tool in your arsenal of performance and recovery enhancing instruments, but only if you are willing to use it the way science has shown it to be effective.  There are quite a few ingredients out there that can be very helpful at increasing training volume or improving recovery, but that may not be convenient when it comes to the traditional timing of pre-workout nutrition.  There are plenty of pre-workout products that contain citrulline malate, though rarely at an effective dose.  Even if the dosage is effective, the recommended timing of ingestion is rarely long enough before training to deliver maximal benefit.  So it is not as simple as “does it work, or not?”  It works, when you use this tool within the guidelines research has provided.  Outside of the correct dosing and timing, though, citrulline malate is very much a waste of time and money.

For more information about citrulline, check out this page at examine.com:


About Kevin Kuhn

Kevin KuhnKevin Kuhn, M.S.Ed., CSCS, MFS is a Kinesiologist and Sport Nutrition Coach in Dallas, Texas, as well as the Vice President of Research and Development for Classified Nutrition (ClassifiedNutrition.com).  Before moving to Dallas in 2012, Kevin was the head strength & conditioning coach for the Indiana Invaders professional running club in Indianapolis, Indiana.  Kevin specializes in athletic performance with great interest and experience in running-specific strength & conditioning, corrective exercise, and exercise and sport nutrition.  Kevin has been certified by the National Strength & Conditioning Association as a Certified Strength and Conditioning Specialist (CSCS) and as a Master Fitness Specialist by the Cooper Institute.

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