5 Health Benefits of L-Citrulline: What You Need to Know

Watermelons are almost everyone's favorite summertime fruit — sweet, juicy, and oh-so-refreshing after a grueling workout. What's not to like?

Aside from their thirst-quenching abilities, watermelons are one of nature's best sources of the amino acid L-citrulline. This specific amino acid has gained popularity as a nitric oxide (NO) booster, with potential benefits for improving aerobic and anaerobic exercise performance.

We'll get into the health and ergogenic benefits more in a minute, but L-citrulline supplements can be a good investment for virtually any adult, regardless of their activity level. Let's dive into the specifics of L-citrulline supplementation and how to use this intriguing non-essential amino acid for proper efficacy.

What Is L-Citrulline?

L-citrulline is a non-essential amino acid synthesized naturally in the human body. It derives its name from the Latin word for watermelon, "Citrullus," as the fruit is one of its most abundant natural sources. Aside from watermelons, L-citrulline can also be found in cucumbers, pumpkins, and various gourds.

L-citrulline supplementation boosts endogenous L-arginine levels and, subsequently, increases blood flow via a chemical called nitric oxide (NO)—this mechanism of action forms the foundation of citrulline's therapeutic potential. Citrulline supplements generally provide either free-form L-citrulline or L-citrulline malate (a salt form of citrulline combined with malic acid).

Why Is L-Citrulline Important?

In the human body, L-citrulline is important for renal physiology (the urea cycle) and blood pressure regulation. L-citrulline is converted into another amino acid, L-arginine, by the kidneys, which increases nitric oxide (NO) production. NO is a critical signaling molecule in cardiovascular and endothelial function, acting as a vasodilator that relaxes and widens blood vessels, thereby enhancing blood flow and reducing systolic/diastolic blood pressure levels

L-citrulline serves as a reservoir of arginine in the body, as the former is converted into the latter in the kidneys. Thus, greater L-citrulline availability indirectly boosts your nitric oxide levels to lower blood pressure/support normal blood pressure.

On the flip side, nitric oxide dysregulation correlates with high blood pressure, heart disease, diabetes, muscle atrophy, and even erectile dysfunction.

L-Citrulline vs. L-Arginine: Which Is Better for Athletic Performance?

You may think that supplementing with L-arginine instead of L-citrulline makes more sense for increasing blood flow. However, a pharmacokinetic study published in The British Journal of Clinical Pharmacology shows that arginine isn't as effective as L-citrulline when it comes to boosting nitric oxide production. 

The Journal of PLOS One also says consuming L-citrulline and L-arginine together leads to pronounced increases in nitric oxide production. Therefore, if you’re going to use one or the other, L-citrulline is better than L-arginine at increasing nitric oxide levels, but for even greater hyperemic effects, consider a dietary supplement with both L-citrulline and L-arginine.

5 L-Citrulline Benefits Backed by Science

Numerous studies have elucidated the benefits of L-citrulline, particularly in the context of cardiovascular health and exercise performance. For instance, clinical research has demonstrated that L-citrulline supplementation can enhance blood flow by increasing nitric oxide production, which in turn may improve exercise performance and contribute to overall wellness.

Below, we'll touch on various L-citrulline benefits to help you understand why this technically "non-essential" amino acid is, in fact, indispensable:

1. Boost Exercise Performance

Many fitness buffs and professional athletes already know about L-citrulline's potency in improving exercise performance. But since many are new to this information, let’s review:

• The British Journal of Sports Medicine explains that citrulline malate increases energy production during exercise.

• Because L-citrulline supercharges your nitric oxide metabolism, your muscle cells can count on more blood flow, and therefore, oxygen and nutrients, during weight-lifting. This also helps delay the onset of muscle fatigue — anything to get in one more bicep curl, right?

If you need further convincing, here's more data:

• The Journal of Strength and Conditioning Research found that healthy subjects who took 8 grams of citrulline malate increased their training volume for lower-body resistance exercises.

• According to The Journal of the International Society of Sports Nutrition, eight days of oral L-citrulline supplementation improved cyclists' exercise performance and reduced post-exercise muscle fatigue.

Whether you're into resistance training or cardio, L-citrulline supplements help amplify your athletic performance.

2. Improve Cardiovascular Functions (e.g. Blood Pressure Levels and Blood Flow)

Taking an L-citrulline can effectively reduce high blood pressure by promoting the relaxation of blood vessels, which is a critical factor in maintaining cardiac function. Research has indicated that regular citrulline supplementation may support improved arterial function and reduce the risk of cardiovascular diseases.

Thankfully, L-citrulline's ability to boost nitric oxide production also helps maintain heart health. Vasodilation improves blood flow and reduces pressure in the blood vessels. The Cardiology Journal also reports that L-citrulline supplements may even help treat heart failure.

3. Enhance Muscle Recovery

Achy, sore muscles don't just call for an ice bath after your workout, they can also prevent you from training for days. Thankfully, L-citrulline helps accelerate post-exercise muscle recovery.

As an intermediate in the urea cycle, L-citrulline promotes nitrogen waste removal from the body, which can reduce muscle fatigue and soreness. Also, The Journal of Nutrients also pointed out L-citrulline's anti-inflammatory abilities. This may help mitigate exercise-related inflammation and subsequent muscle soreness.

4. Bolster Lean Body Mass

Another health benefit of L-citrulline supplements is protecting skeletal muscle tissue from atrophy.

The Journal of Cachexia, Sarcopenia, and Muscle found that the effects of citrulline administration aren't only limited to energy production. It also directs part of your body's energy (in the form of adenosine triphosphate/ATP) towards muscle-building.

Also, a Citrudose pharmacokinetic study in The British Journal of Nutrition tested the effect of oral L-citrulline supplementation on plasma amino acids and hormonal patterns. The results showed higher levels of citrulline, arginine, and ornithine after supplementation.

Since amino acids are the building blocks of protein in muscle fibers, more plasma amino acids would mean more muscle growth.

Meanwhile, The European Journal of Applied Physiology says that L-citrulline malate raises growth hormone levels during exercise, which may also elevate protein synthesis and facilitate fat burning.

5. Manage Erectile Dysfunction

This may sound a little unexpected, but the health benefits of L-citrulline extend—no pun intended—to erectile function in men. The penis depends on proper blood flow to achieve and maintain a strong erection; naturally, researchers have investigated the effects of L-citrulline on erectile dysfunction. 

According to The Journal of Urology, one month of oral L-citrulline supplementation significantly improved symptoms of mild erectile dysfunction with no side effects.

Is it Safe to Take L-Citrulline?

While L-citrulline is generally well-tolerated with no significant side effects reported in clinical studies, it is important to be aware of some potential issues that may arise. Some individuals have experienced mild gastrointestinal discomfort when initially starting L-citrulline (malate) dietary supplements.

To mitigate GI side effects, it is recommended to begin with a lower dose of L-citrulline and gradually increase as tolerated. This can help the digestive system acclimate without causing significant distress. It is also advisable to take L-citrulline with food, which may further alleviate gastrointestinal discomfort. 

Individuals with specific health conditions or those currently taking certain medications should exercise caution when considering L-citrulline supplementation. This is particularly relevant for individuals managing hypertension (elevated diastolic/systolic blood pressure), cardiovascular disease, diabetes, or atherosclerosis. Additionally, pregnant or breastfeeding individuals are advised to avoid L-citrulline due to the lack of sufficient evidence regarding its safety in these populations. 

How to Use L-Citrulline Supplements

Ready to reap the L-citrulline benefits mentioned above? Before you head to the grocery store to stock up on watermelon, be aware that you'll have to eat about 2 pounds of watermelon flesh per day to reach the minimum effective dose of 2 g L-citrulline.

Thankfully, L-citrulline supplements are a practical and cost-effective option to fill the watermelon void. Here's how to use them properly:

• Dosage Recommendations: For general health and cardiovascular benefits, a daily intake of 3 grams of L-citrulline is considered effective. For athletic performance enhancement, particularly in endurance and strength sports, dosages can range from 6 to 8 grams per day. Citrulline malate, which combines citrulline with malic acid, is often used prior to resistance training and may be taken in doses ranging from 6 to 10 grams per day.

• Timing and Absorption: For exercise-related purposes, it is recommended to take L-citrulline or citrulline malate approximately 30 to 60 minutes before working out to enhance blood flow and oxygen delivery to muscle tissue. For general health benefits, L-citrulline can be consumed at any convenient time during the day, with or without food, as it does not have significant interactions with meals. Consistency in daily intake is key to achieving the desired outcomes, and splitting the dose into two smaller servings might improve absorption and reduce potential gastrointestinal discomfort.

Those who want an extra energy boost and increased blood flow on intense gym days can grab a bottle of PreSeries Pre-Workouts, each of which contains 6-8 grams of L-citrulline (malate) per serving.

Maximize Your Athletic Performance and Muscle Recovery

L-citrulline (malate) has been researched extensively, and new studies continue to unveil the many health benefits of this biologically important, albeit non-essential, amino acid. Attention has been given to its role in enhancing exercise performance through augmented blood flow and oxygen delivery, as well as its potential cardiovascular benefits and anti-hypertensive properties.

Noteworthy findings indicate that chronic L-citrulline supplementation may protect against acute endothelial dysfunction, reduce vascular stiffness, and promote adaptive responses to physiological and environmental stressors. Additionally, its systemic effects may have a positive impact on conditions such as hypertension, atherosclerosis, inflammation, insulin resistance, type 2 diabetes, and cardiovascular disease. 

Whether you're looking to improve athletic performance, build muscle tissue, or support cardiovascular health, incorporating an L-citrulline supplement into your fitness regimen will be well worth the price of admission.