L-Citrulline vs. L-Citrulline Malate: Which Is the Best Nitric Oxide Booster?

L-citrulline is a nonessential alpha-amino acid that is organically produced in the rind and flesh of watermelons. This amino acid is crucial for nitric oxide production and eliminating nitrogen from the body.

Given the nitric oxide-boosting properties of L-citrulline and its effects on exercise performance, it's become a common pre-workout ingredient. However, L-citrulline supplementation is a bit confusing since it comes in two similar yet distinct forms: pure L-citrulline and L-citrulline malate.

This article will help you understand the differences between L-citrulline vs. citrulline malate, how they work, their health benefits, and which is best for athletic performance.

Difference Forms of L-Citrulline found in Supplements

If you have a pre-workout supplement in your cupboards, odds are it contains either citrulline or citrulline malate. But what's the difference between these two forms of citrulline?

In short, supplements that list "L-citrulline" on the label contain pure L-citrulline in its native amino acid form. If a supplement lists "L-citrulline malate" as an ingredient, that means it contains the citrulline salt of malic acid.

Typically, citrulline malate comes as a 2:1 ratio of citrulline to malic acid. This means a 6,000 mg dose of citrulline malate contains 4,000 mg of citrulline and 2,000 mg of malic acid. Keep that in mind when you're looking for pre-workout supplements with effective doses of citrulline (e.g. 3,000 - 6,000 mg).

Role of Citrulline in Nitric Oxide Production

L-citrulline primarily bolsters nitric oxide-dependent signaling but also plays myriad physiological roles throughout the body. It is an important component of the urea cycle that's synthesized in the liver by a variety of other amino acids; the urea cycle facilitates the elimination of ammonia and other nitrogenous toxins from the blood.

Nitrogen metabolites accrue from the digestion, absorption, and metabolism of proteins. Given that bodybuilders and health enthusiasts generally consume large amounts of protein, proper nitrogen metabolism is crucial for keeping blood urea nitrogen (BUN) levels in a healthy range.

Oral citrulline supplementation has been demonstrated to elevate blood plasma levels of L-arginine and thus augments the production of L-arginine metabolites (such as creatinine, nitrite, and ornithine) [1]. The synthesis and elimination of these metabolites are necessary for removing nitrogenous metabolites from the body. L-citrulline works along with citric acid, aspartic acid, and magnesium to improve nitrogen metabolite excretion.

In exceptionally rare instances, a disorder called citrullinemia may occur in humans; this condition occurs when there is a deficiency of the enzyme necessary to catalyze the L-citrulline --> L-arginine reaction of the urea cycle.

Research suggests that supplementing with the mineral zinc can enhance the conversion of L-citrulline to L-arginine in the liver, and lower blood ammonia levels [2]. Since pyridoxine (vitamin B-6) activates enzymes that convert an amino acid to another amino acid (called transaminases) in the urea cycle, it may be another useful to ancillary to citrulline supplementation.

That being said, such clinical abnormalities should always be addressed by a qualified medical professional or personal care physician before taking any form of citrulline supplement.

Health Benefits of L-Citrulline vs. Citrulline Malate

Pure L-citrulline and L-citrulline malate both have a strong body of empirical evidence supporting their benefits in the realms of athletic performance and cardiovascular health. Aside from being a necessary amino acid of the urea cycle, L-citrulline (malate) supplements may enhance health and exercise performance through several mechanisms, including [3, 4]:

• Elevating nitric oxide (NO) production, a positive for expanding blood vessels and increasing blood flow
• Enhancing elimination of toxic nitrogen metabolites
• Enhancing the utilization of essential amino acids during exercise
• Improving recovery time after exercise by attenuating delayed-onset muscle soreness
• Reducing/inhibiting muscle protein breakdown
• Increasing growth hormone levels to a higher degree in individuals after resistance training as compared to a placebo group
• Lowering blood pressure (which may help treat erectile dysfunction in men)

It's unclear if the citrulline salt of malic acid is better for exercise performance. Malic acid (malate) supplementation is lacking in human research [5]; more data is necessary to determine any additional benefits it confers for athletes and gym-goers.

Does Citrulline Reduce Blood Pressure?

There is substantial evidence that taking citrulline supplements can reduce blood pressure in hypertensive patients [4]. As such, supplements that contain citrulline may be useful for erectile dysfunction in men and promoting healthy cardiovascular function.

As a side note, citrulline supplements appear to be more effective than L-arginine at lowering blood pressure [5].

Who May Benefit from Citrulline Supplementation

• Bodybuilders and powerlifters
• Athletes looking to increase their exercise performance capacity
• Those looking to improve blood flow and muscle pumps during workouts
• Individuals with high blood pressure* (*do not take citrulline as a replacement for prescription medications or medical advice)
• Patients with urea cycle defects*

Taking L-Citrulline (Malate): Dosage Recommendations

• Start with a once-daily dose of 6-8 grams of citrulline
• Optimally, citrulline should be ingested about 15-30 minutes before training
• An additional post-workout serving of citrulline may enhance muscle recovery
• If desired, the dose may be increased to 15-20 grams split into multiple doses throughout the day

Potential Side Effects of L-Citrulline (Malate)

Unlike some nitric oxide boosters, citrulline is generally well-tolerated and transient side effects are uncommon. However, those with citrullinemia, a genetic disorder of the urea cycle, should avoid citrulline supplements as they will exacerbate the condition.

Some people supplementing with citrulline may notice slight gastrointestinal distress, but this can be mitigated by taking citrulline on an empty stomach.

L-Citrulline vs. Citrulline Malate FAQ

Q: I’ve heard L-citrulline and citrulline malate should be taken on an empty stomach, is this true?

A: This is likely due to the rare occurrence of stomach distress side effects that may occur after ingesting citrulline; it's fine to take citrulline with or without a meal, depending on how you tolerate it.

Q: How long will it take to notice the effects/benefits of citrulline?

A: This will vary for most individuals, but acute effects such as endotoxin removal will happen after the first dose. More progressive benefits such as strength increases and decreased delayed-onset muscle soreness may take a few weeks to notice.

Q: Is it true citrulline might enhance libido and treat erectile dysfunction?

A: This is actually another nice “benefit” of citrulline supplementation as the increase in nitric oxide will relax blood vessels and increase blood flow (which can help improve erections, among other things).

Q: Can I just eat watermelon rather than taking L-citrulline?

A: Unfortunately, it’s not very practical to obtain the doses of citrulline suggested herein through diet, and most of the citrulline found in watermelon is actually in the rind of the fruit, not the flesh (the most edible part). Nevertheless, some people claim that drinking watermelon juice is as effective as using an L-citrulline supplement.

Best Citrulline Supplements Before Hitting the Gym

Now that you have a better grasp of the different forms of citrulline found in dietary supplements, be sure to check out the range of Jacked Factory pre-workout powders!

You may notice that ALTIUS Pre-Workout contains a much higher amount of L-citrulline malate than most pre-workout powders. The reason for that is many companies use a minimal dose of citrulline in their products just to make them seem better when all they really are is under-dosed garbage. Each serving of ALTIUS provides an evidence-based dose of L-citrulline malate, yielding 4,000 mg of citrulline.

Use the stim-free pre-workout PUMPSURGE if you prefer a supplement without caffeine before you hit the gym. PUMPSURGE contains 5,000 mg of pure L-citrulline in every serving.