5 L-Citrulline Benefits Backed By Science (Plus 1 You're Overlooking!)

Authored by Elliot Reimers, M.S.(C), CISSN, CNC

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 its thirst-quenching abilities, watermelons are also rich in L-citrulline — an amino acid that's highly popular due to its range of health benefits, like enhancing athletic performance and promoting heart health.

Whether it's for the gym or daily wellness, L-citrulline can benefit virtually anyone. So, we wrote a guide to get you up to speed on L-citrulline benefits and how to use this intriguing amino acid supplement.

What Is L-Citrulline?

l citrulline benefits: chemical formula

L-citrulline (or citrulline) is derived from Citrullus vulgaris, which is the scientific jargon for the watermelon fruit. It's also produced in your small intestines, making it a non-essential amino acid.

While L-citrulline has traditionally been used to treat urea cycle disorders (UCDs) and kidney damage, the amino acid can also be found in dietary supplements to boost your body's citrulline (and by extension, L-arginine) levels, according to the Food and Drug Administration (FDA).

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?

L-citrulline benefits are mainly linked to nitric oxide metabolism. The main benefit of nitric oxide is vasodilation — it relaxes and widens your blood vessels to increase blood flow — which is linked to better heart health and athletic performance.

Here’s the link between L-citrulline and nitric oxide metabolism: The Journal of Nutrients explains that a precursor called L-arginine regulates nitric oxide production in your body, and higher arginine levels produce more nitric oxide. L-citrulline serves as a reservoir of arginine in the body, as the former is converted into the latter in the kidneys. So, higher L-citrulline content indirectly boosts your nitric oxide levels.

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

To recap:

  • Higher nitric oxide content is beneficial for your health as it expands blood vessels and supports cardiovascular function.
  • L-citrulline and arginine supplementation increases your body's nitric oxide levels.

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

    At this point, you may think that it makes more sense to just supplement with L-arginine instead of L-citrulline for increasing nitric oxide levels.

    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 led to the largest increase 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. For even higher nitric oxide production, consider a dietary supplement with both L-citrulline and L-arginine.

    5 L-Citrulline Benefits You Need to Know

    Below, we'll touch on various L-citrulline benefits to help you understand why this non-essential amino acid is actually pretty essential.

    1. Enhance Exercise Performance

    man in the gym looking at his tumbler

    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:

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

    2. Speed up 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.

    3. Promote Muscle Growth

    One of the many L-citrulline benefits is increased muscle mass and strength.

    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.

    4. Improve Heart Health

    As you age, your body is less efficient in producing nitric oxide. Lower levels of nitric oxide heighten the risk of cardiovascular diseases and high blood pressure.

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

    5. Manage Erectile Dysfunction

    This may sound a little unexpected, but L-citrulline benefits can even help with 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.

    In other words, you might want to skip the Viagra (which can cause a range of  side effects, notably headaches and stomach problems) and take an L-citrulline supplement instead.

    Is it Safe to Take L-Citrulline?

    While there are many L-citrulline benefits, some may be concerned about its safety as a dietary supplement.

    To set your mind at ease, know that the FDA states L-citrulline supplements are safe for consumption, even at relatively high doses. A Citrudose pharmacokinetic study backs this up, as healthy subjects responded well to a daily dose of 15 grams of citrulline.

    With that said, minor side effects of L-citrulline such as nausea and indigestion may occur. L-citrulline supplements may also interact with other medications for heart disease and high blood pressure.

    As such, it's best to consult a healthcare professional to see if an L-citrulline supplement is right for you.

    Get More L-Citrulline Through Your Diet

    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.

    For a high-quality citrulline powder supplement, check out Transparent Labs RawSeries Fermented L-Citrulline. With 2 grams of pure L-citrulline per scoop, this vegan-friendly supplement is the perfect addition to your pre-workout and post-workout shakes.

    Those who want an extra energy boost on intense gym days can grab a bottle of PreSeries Stim-Booster — it contains 2 grams of L-citrulline, Infinergy™ Di-caffeine malate, caffeine, and theobromine for greater blood flow and focus during training.

    But if you want to kick your caffeine habit to the curb, the PreSeries STIM-FREE Pre-Workout is ideal before hitting the gym. This stimulant-free pre-workout powder features clinically effective doses of citrulline malate, beta-alanine, betaine anhydrous, and several other ergogenic ingredients to help you perform at peak capacity without the unwanted side effects of being overstimulated.

    Maximize Your Athletic Performance and Muscle Recovery

    Unlike other ergogenic supplements that are largely for athletic performance goals, L-citrulline is a 2-in-1 dietary supplement that maximizes both your fitness and general health. Enhancing exercise performance, reducing muscle soreness, and improving heart health are just some of the major L-citrulline benefits.

    To ensure you're checking off every health and fitness goal, supplement your body's L-citrulline levels with the right diet. Watermelons may get the job done, but they aren't as effortless as popping a scoop of L-citrulline supplement into your pre-workout drink — time to click "Purchase" on that dietary supplement you've been eyeing.

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