Athletes looking to elevate their strength or performance are constantly seeking a competitive edge, and they often turn to supplements for that boost. A popular supplement amongst strength athletes is citrulline malate. But it’s important to understand whether the science supports the intended use of a supplement before introducing it into a daily routine. So, does research support the use of citrulline malate for athletic performance? Or are these athletes investing in an ineffective solution?

This article takes a deep dive into how citrulline malate supplements work, why they impact performance, and other considerations of supplementation.

What is citrulline malate?

Citrulline malate consists of two parts: citrulline and malate. Citrulline is a naturally occurring amino acid, and malate is an organic salt of malic acid (a compound found in some fruits). Together, they play a critical role in the body’s energy production. [1]

Citrulline supplements without the malic acid (AKA L-citrulline) may have some similar benefits, however, the impact on energy production likely isn't as profound. [2] 

How does citrulline malate work in the body?

Multiple pathways and cycles are needed to convert calories from food into energy the body can use. And those pathways differ depending on whether the energy comes from carbohydrates, fats, or proteins. Malate, in particular, helps regulate enzymes involved in the breakdown of glycogen (the storage form of carbohydrates) into energy.

Arginine is an amino acid that’s also involved in energy production. Studies show that citrulline is readily available to be converted to arginine in the body. And citrulline malate supplements can actually increase arginine levels more than arginine supplements. [1] Here's how that increased arginine affects physical performance. 

1. Increasing nitric oxide: Arginine produces nitric oxide, which acts as a vasodilator to widen blood vessels and improve blood flow. Efficient blood flow throughout the body is particularly important during intense exercise and is associated with improved performance. [1]
2. Removing ammonium through the urea cycle: When muscle breaks down—characteristic of strenuous exercise—ammonium can build up in the blood and lead to fatigue. As a component of the urea cycle, arginine assists in clearing ammonium from your system. So increasing arginine likely reduces fatigue, expedites muscle recovery, and contributes to muscle gain. [1] 
3. Clearing lactic acid from worked muscles: Lactate builds up in muscle tissue and is used for energy during anaerobic exercise. However, high lactate may be the culprit of fatigue. Therefore, arginine’s role in clearing lactate contributes to improved muscle function. [1] 

How does citrulline malate impact athletic performance?

Citrulline malate may enhance strength and endurance performance due to its positive impact on blood flow and muscle health. 

Citrulline malate improves measures of strength performance

One small trial of 12 advanced resistance-trained males investigated the impact of citrulline malate supplements on lower-body exercise repetitions to failure. Men who took 8g of citrulline malate before exercising performed significantly more repetitions of leg presses, leg extensions, and hack squats than their non-supplementing counterparts. [1] 

Another study looked at the impact of 8g of citrulline malate on upper body exercise performance in 14 resistance-trained men. Citrulline malate significantly increased the number of repetitions performed for multiple activities: regular (+12.5%) and reverse chin-up repetitions (+18.7%), and push-up repetitions (+9.2%). [3] And, a study of 41 men found that supplementing with a single dose of citrulline malate correlated with a 53% increase in repetitions and lower levels of fatigue compared to the control group. [4]

Women may also benefit from citrulline malate supplements. Taking 12g of citrulline malate improved Wingate peak power and max grip strength in 17 elite female tennis players. [5] In addition, supplementation improved max reps in upper and lower body exercises and improved their rate of perceived exertion (RPE) during exercise in a study of 15 resistance-trained females. [6]

Key takeaway: Trained athletes taking citrulline malate supplements saw notable strength performance improvements, including the number of repetitions to fatigue. 

Citrulline malate improves measures of strength performance

Optimizing post-workout recovery is crucial for strength performance gains. Research shows that citrulline malate supplements may reduce muscle soreness after exercise by up to 52.8%. [4, 7] Not only does citrulline malate significantly improve muscle soreness, but this supplement appears to stimulate muscle protein synthesis, a key component of muscle building. [8] For more strength recovery tips, check out this article. 

Key takeaway: Citrulline malate supplements may reduce muscle soreness after exercise and promote muscle growth.

Citrulline may also enhance endurance performance

A trial including 22 trained males compared cycling performance after seven days of supplementing with either citrulline or a placebo. The researchers found that those in the citrulline group completed the timed trial 1.5% faster than the placebo group. [2] While many studies show anaerobic exercise benefits, further studies are warranted to understand how this supplement can improve aerobic exercise performance. However, this citrulline supplement was in the form of L-citrulline, not citrulline malate. 

Check out this article on how to level up your endurance exercise. 

Key takeaway: Citrulline supplements may improve endurance performance, but further research is warranted.

Are there other benefits of citrulline supplementation?

Citrulline malate and L-citrulline supplements have also been studied for various health conditions. 

Citrulline may or may not improve measures of heart health

Because citrulline malate supplements are vasodilators, they’ve also been studied for impacts on heart health measures like blood pressure, resting heart rate, and more. However, three studies found no improvements in resting heart rate when using citrulline malate supplements. [1,6,9] Researchers are continuing to explore this relationship, but in the meantime, here are science-backed ways to improve heart health. 

Citrulline supplementation does not boost testosterone levels

Citrulline malate has also gained a reputation for increasing testosterone levels. But those claims aren't supported by scientific evidence, and the impact citrulline malate supplements have on athletic performance are not related to testosterone  levels. [10]

Citrulline may improve blood flow in men with erectile dysfunction

Citrulline may positively impact erectile dysfunction (ED). A study found that men with partial or complete ED had lower levels of citrulline and arginine. Taking citrulline increases nitric oxide and then blood flow, a cornerstone of improving ED. [11] Consult with your doctor before supplementing with citrulline for ED.  

Who should take a citrulline malate supplement?

Studies have mainly looked at the impact of citrulline malate supplementation in highly active young adults—who may benefit the most from this supplement. While these studies show positive effects on performance outcomes, they do have small sample sizes, and findings must be generalized with caution.

Consult your physician before taking any nutritional supplements.

When and how much citrulline should you take?

A citrulline malate dose of 8-12g taken before exercise is most beneficial for measures of athletic performance. [1,4-6] Aim for approximately 2.5g of L-citrulline if you select this supplemental form. Citrulline can be taken with or without food or dissolved in at least eight ounces of liquid.

Are citrulline malate supplements safe?

Citrulline malate supplements are considered safe, and studies report no adverse events among participants taking the supplement. But, these studies are pretty short term, lasting less three months. Long-term supplementation of citrulline malate should be considered with caution. 

Is citrulline found in food?

Watermelon, or Citrullus vulgaris, is the most potent dietary source of citrulline. [12] The watermelon rind holds the highest concentration of citrulline compared to the flesh. [13]

While watermelon is the primary food source for citrulline, it’s not the only food that can increase nitric oxide production in the body. Nitrate-rich vegetables like spinach and celery can also increase nitric oxide. A crossover study showed that the nitrates in spinach effectively improved blood pressure and other measures of heart health. [14] Beetroot juice and tart cherry juice provide concentrated sources of nitrates and may also improve blood flow in athletes. [15, 16]

Summary of key points

• Citrulline malate likely plays a critical role in the body’s energy production. 
• Citrulline is readily available to be converted to arginine, which acts as a vasodilatory to improve blood flow. 
• Trained athletes taking citrulline malate supplements saw notable strength performance improvements including the number of repetitions to fatigue and reduced muscle soreness.
• InsideTracker recommends citrulline malate supplements to active adults specifically working towards strength and endurance goals.

Connecting InsideTracker

The science on citrulline malate is now robust enough that InsideTracker recommends citrulline malate for active individuals focusing on improving their strength and performance. InsideTracker also has recommendations for other natural vasodilators like beetroot juice and tart cherry juice for active individuals. Curious to know what your personal recommendations are? InsideTracker's Ultimate Plan is the most comprehensive option for athletes with lofty performance goals. Learn more about the plan here. 

Michelle Darian, MS, MPH, RD

References

[1] https://pubmed.ncbi.nlm.nih.gov/25226311/

[2] https://pubmed.ncbi.nlm.nih.gov/26900386/

[3] https://pubmed.ncbi.nlm.nih.gov/25674699/

[4] https://pubmed.ncbi.nlm.nih.gov/20386132/

[5] https://pubmed.ncbi.nlm.nih.gov/27017895/

[6] https://pubmed.ncbi.nlm.nih.gov/26658899/

[7] https://pubmed.ncbi.nlm.nih.gov/30458655/

[8] https://pubmed.ncbi.nlm.nih.gov/24972455/

[9] https://pubmed.ncbi.nlm.nih.gov/31456449/

[10] https://pubmed.ncbi.nlm.nih.gov/29057836/

[11] https://pubmed.ncbi.nlm.nih.gov/28178400/

[12] https://pubmed.ncbi.nlm.nih.gov/27749691/

[13] https://pubmed.ncbi.nlm.nih.gov/16007998/

[14] https://pubmed.ncbi.nlm.nih.gov/26251834/

[15] https://pubmed.ncbi.nlm.nih.gov/25846114/

[16] https://pubmed.ncbi.nlm.nih.gov/28696985/