Citrulline May Help with Strength Performance and Delay Fatigue. What Are Its Other Benefits?

Citrulline is not as well known in sports nutrition as protein or creatine, but it definitely deserves attention. It is especially popular with strength athletes who take it before training with the goal of pumping up their muscles. However, they don’t do it just to look bigger and crave the admiring glances of other gym-goers. Thanks to muscle pumping, they’ll have the area in question well perfused with blood, which will translate into improved strength performance. But the effects of citrulline are far from over. In fact, it offers a number of benefits for strength and endurance athletes and also has interesting health benefits, which you will discover today.

In this article you will read about the effects of citrulline on these specific areas:

What is citrulline?

Citrulline is a non-essential amino acid that the body can make itself. In the body, it is produced as an intermediate from the amino acid ornithine and carbamoyl phosphate as part of the urea cycle. At the same time, you naturally ingest it from certain foods or supplements. Unlike other amino acids you know from sports nutrition, citrulline is not used in the body as a building block for the growth or regeneration of muscles and other tissues. However, it has a completely different function that is just as important for athletes. ^[3]

An interesting fact about citrulline is that the name was derived from the Latin word citrullus vulgaris, which translates as watermelon. It was from watermelon that the substance was first isolated in 1914. ^[7]

If you are interested in other amino acids and want to learn more about their effects, read our article Amino Acids: Classification, Functions in the Body, Effect on Athletic Performance and the Best Sources.

How does citrulline work?

Citrulline is involved in two key processes in the body. The first is the aforementioned urea cycle. This takes place mainly in the liver and is important for the removal of toxic ammonia from the body and its conversion to less toxic urea, which is then excreted in the urine. In addition to citrulline, ornithine and arginine are also involved in this detoxification process. In this way, citrulline is involved in processes related to the body’s natural detoxification. ^{[1, 3]}

The second process, which will be of greater interest to athletes, is the production of nitric oxide (NO). Citrulline can be converted into the amino acid arginine in the body. From this, nitric oxide is then formed, which has the effect of dilating blood vessels (vasodilation). This allows better blood flow to the tissues, which results in a greater muscle pump. This allows more oxygen and other nutrients to reach the muscles, and also results in more efficient removal of waste products of energy metabolism. All of this can result in better athletic performance.

What’s the difference between citrulline and arginine?

You may have immediately thought why take citrulline when you can just take arginine, which produces nitric oxide. The tricky part, however, is that your body can’t use the ingested arginine as efficiently as citrulline.

When you take arginine, it must first be metabolised in the gut and liver. This can reduce the amount of it in the blood, which is then available for the formation of nitric oxide. In contrast, most of the citrulline ingested goes straight into the blood where it is used for conversion to arginine. ^[3]

Researchers have also compared whether l-arginine or l-citrulline increases arginine levels in the body to a greater extent. In most studies, they concluded that l-citrulline supplementation is indeed more effective in this regard. Ultimately, it can produce more NO, which also means increased muscle circulation. ^[4]

However, studies also show that a combination of both amino acids can work well. That’s why a number of complex supplements contain both l-citrulline and l-arginine. ^{[2, 5]}

If you also want to learn more about arginine, you shouldn’t miss our article Arginine: Effects and Dosage for Athletic Performance and Health.

What is the difference between l-citrulline and citrulline malate?

Citrulline is most commonly found in supplements in the form of l-citrulline or l-citrulline malate (CM). In the second instance, the amino acid l-citrulline forms a complex with a salt of malic acid known as malate. The latter is involved in the body’s Krebs cycle, which produces ATP, the basic source of cellular energy. It serves as an energy fuel for the muscles, brain and basically the entire body. It thus has a more comprehensive effect on energy production, which is why this form is more often recommended to athletes. ^[1] 

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What are the effects of citrulline?

Thanks to its properties, citrulline has an effect not only on athletic performance, but also on some areas of your health.

1. Sports performance

Citrulline is most often sought after by athletes hoping for better performance in the gym, on the running track and during a long cycling stage. What effects does science say it has?

• Helps reduce fatigue: During intense sports activity, the body produces more ammonia, which can increase the production of lactate (lactic acid) and cause muscle fatigue. Supplementation of citrulline can promote ammonia uptake, ultimately delaying fatigue and prolonging athletic performance, according to some studies. In addition, malate can prevent lactic acid build-up by helping to convert it into energy. ^{[6, 14]}
• Promotes energy production: This has been shown especially with CM. In fact, the malate contained can increase the production of ATP, the basic unit of cellular energy. ^[6]
• May improve strength performance: Studies show that citrulline supplementation can help you handle a higher number of reps and total training volume (reps × sets × load). This is mainly due to improved blood flow or the citrulline pump. This is because more oxygen and nutrients, i.e. fuel, get to the pumped muscles to help you get the most out of yourself.
• It helps you cope with high-intensity training: By delaying fatigue and supporting muscle function, it can also support high-intensity performance such as sprint running, HIIT (High Intensity Interval Training) or short CrossFit WODs (Workout Of The Day).^[8]
• It can boost endurance performance: In one study, for example, citrulline supplementation led to an improved time on a 4km ride on a cycle trainer. Participants also reported feeling less muscle fatigue. However, the beneficial effect of citrulline has not yet been confirmed for extended workout sessions. ^[9–10]

Citrulline supplementation can thus pay off for every athlete who strength trains at high intensity or wants to delay muscle fatigue. In the case of endurance athletes, the results are not entirely clear, but the physiology applies to everyone, so citrulline could have its role to play in their case as well.

What do you combine citrulline with to support athletic performance?

Citrulline can also be combined with other supplements that contribute to athletic performance.

• Creatine: It supports the recovery of ATP, which is the main source of energy for working muscles. Thanks to this, it increases physical performance during intense workouts.
• Arginine: Another NO supplement to help pump up your muscles and get them ready for training.
• Beta-alanine: It forms carnosine, which helps regulate muscle acidification during workouts.
• Caffeine: It will help energise you before a workout and keep you alert and focused.
• Pre-workout complex: Contains citrulline, arginine, beta-alanine and other substances to help prepare the body for performance.

2. Muscle growth

Although citrulline does not build muscle, it can still support the whole process of building active body mass. Scientists have found that it can activate the mTOR (Mammalian Target of Rapamycin) signalling pathway, which is at the origin of processes related to cell growth (muscle growth and anabolic events) and muscle protein formation MPS (Muscle Protein Synthesis). ^[1]

In addition, citrulline can promote the use of other amino acids, especially leucine, isoleucine and valine (BCAA) during exercise. This in turn can help to suppress catabolism (the breakdown of muscle tissue). The positive effect on muscle protection and growth is probably also due to an increase in growth hormone levels, which has also been observed when taking citrulline. ^[11]

In addition, it has been found that under energy-intensive conditions (insufficient energy intake, high energy expenditure), citrulline can redirect energy in the form of ATP, which is produced in the mitochondria, to be used for muscle formation. ^[12]

But you must not forget one more factor that can play a significant role in building muscle mass. When you train longer, at a higher intensity or do more reps with heavy weights as a result of taking citrulline, your muscles get a bigger training boost than without it. The body then responds to this load with adaptive processes that lead to muscle growth. Thus, the principle of progressive overload, which is the alpha and omega of building muscle mass and improving performance, is fulfilled.

What can you combine citrulline with to promote muscle growth?

You can also support building active mass with other nutritional supplements.

• Protein: A concentrated source of protein that promotes muscle growth as well as muscle protection.
• EAA: Contains essential amino acids that your body cannot produce on its own. They are used to form muscle mass or hormones.
• Gainer: A protein and carbohydrate complex to help increase energy and protein intake.

If you are trying to gain muscle and are wondering how to boost this, then you should not miss our article What to Eat and How to Exercise to Finally Gain Muscle?

3. Regeneration

Quality recovery after exercise is crucial not only for muscle growth, but for overall body regeneration and preparation for the next workout. Citrulline can help here too. It is no coincidence that many people like to take it after a workout.

The main mechanism of this effect is probably the effect of citrulline on the removal of ammonia produced in the body during training. In addition, better blood flow to the muscles may contribute to more efficient removal of other waste products that are produced during muscle work. Likewise, nutrients needed to repair damaged tissue such as muscles or ligaments can reach the muscles better. ^[13]

Another study also found a link between citrulline intake and reduced post-exercise Delayed Onset Muscle Soreness (DOMS). Taking 8 g of citrulline malate before training resulted in a 40% decrease in sore strained muscles 24 and 48 hours after training. The authors of the study conclude that athletes who train at high intensity, prepare for competitions or have a high overall training volume will benefit most from taking citrulline malate. ^[14]

However, endurance athletes can also benefit from these effects. In one study, for example, runners drank 500 ml of watermelon juice enriched with citrulline before a half marathon. After completing the lengthy run, they reported reduced muscle pain in the 24 to 72 hours after reaching the finish line. ^[15]

What can you combine citrulline with to support recovery?

It’s not just citrulline that can help you recover faster after a workout.

• Whey protein: It has a favourable representation of amino acids, which are necessary for the start of recovery processes after training.
• Complex joint nutrition: Usually contains chondroitin, glucosamine, MSM and other substances that help with musculoskeletal system care.
• Quick carbs: They will help replenish stored levels of the carbohydrate glycogen, which will then be available as an energy source for the next workout.

For more ways to boost recovery, read our article How to Boost Recovery with a Massage Gun and Other Aids?

4. Heart health

Not only your muscles, but also your heart and blood vessels benefit from the effects of citrulline. This is mainly due to its ability to convert into nitric oxide (NO). This is because it is involved in dilating blood vessels, and helps to maintain normal blood pressure. It also plays a role in protecting blood vessels from the deposition of atherosclerotic plaque, which can lead to atherosclerosis (blockage of blood vessels) and an increased risk of heart attack. NO also helps to keep the surface of blood vessels smooth, preventing the formation of thrombi (blood clots). However, the body’s ability to make NO may decline with age. Lower levels of this substance are then a risk factor for developing high blood pressure (hypertension) and other heart and blood vessel diseases. ^[17–18]

Therefore, researchers began to investigate whether citrulline supplementation could help increase NO levels and support cardiovascular function. As a result, they found that this substance may indeed be beneficial for cardiovascular function. A number of studies have confirmed beneficial effects on blood pressure in people with elevated blood pressure. Citrulline has even proven itself as a complementary treatment for heart failure. ^[16–18]

With what can you combine citrulline for a healthy heart?

There are other supplements that also have a beneficial effect on the heart.

• Omega 3 fatty acids: They contain the main omega-3 fatty acids in the form of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), which are beneficial fats that support a healthy heart.
• Vitamin D: Supports proper immune function and overall health.
• Antioxidant Complex: A combination of minerals, vitamins and natural antioxidants such as resveratrol, quercetin or curcumin. Ideal for heart care and overall vitality.

You can also support your heart and overall health with regular sports activity. To learn more about the benefits of physical activity, see our article Why Play Sport and Exercise? Stronger Immunity, Heart and 8 Other Reasons.

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5. Sexual health

According to studies, citrulline is also beneficial for male sexual health, specifically erectile function. Erection is accompanied by dilation of blood vessels (vasodilation) and their relaxation, which is influenced by nitric oxide, which is indirectly produced from citrulline.

A number of studies have also confirmed the positive effects. In one, participants took 1.5 g of l-citrulline daily for 1 month. At the end of the study, 12 out of 24 men reported improved erectile dysfunction and greater satisfaction with their sex life. ^[19]

With what can you combine citrulline for sexual health support?

Men can also support their sexual health with other supplements.

• Tribulus Terrestris: An extract which is used in the care of hormonal health and muscle mass.
• D-Aspartic Acid (DAA): An amino acid involved in the production of growth hormone and testosterone.
• Fenugreek A plant extract containing steroidal saponins that are used in testosterone and libido care.
• AlphaMale Testobooster: A vitamin, mineral, adaptogen and herbal extract complex designed to support men’s health.
• Ashwagandha: It is one of the more popular adaptogens and research shows that it can also support optimal hormonal balance.
• Maca: A plant extract that is beneficial for sexual health care.
• Ginseng: An adaptogen that is known for its beneficial effects on sexual health and vitality.

If you’re wondering what other substances and nutrients can help support men’s health, open our article Men and Nutrition: The Most Important Vitamins and Minerals for Health, Testosterone, and Performance

6. Other effects of citrulline

Citrulline is also being investigated in a number of other areas, such as its effect on cognitive function (memory and learning), metabolism, regulation of insulin hormone levels, and type 2 diabetes. Similarly, scientists are also looking at its anti-inflammatory effects. ^{[1, 20]}

What foods contain citrulline?

Normally you find amino acids in protein sources such as meat, eggs or dairy products. However, citrulline can also be found in a completely different category of foods, namely vegetables. The richest source of this amino acid is found in watermelon, after which it was named.

• Watermelon contains approximately 2.1 mg of citrulline in 1 g of flesh. ^[21]
• For an intake of 10 g of l-citrulline, a person would need to eat approximately 3-5 kg of watermelon. ^[6]
• Other sources are yellow or sugar melon, cantaloupe, pumpkin, cucumber or zucchini.

Having watermelon as a pre-workout snack will be a value-added refreshment in the summer. However, no one can manage to eat 3 kg of watermelon in one sitting to take in an effective amount of citrulline without digestive problems. Moreover, watermelon is more than 90% water, so you would probably have to alternate each set of exercises with a visit to the toilet. That’s why it’s better to bet on nutritional supplements.

How should you take citrulline?

The recommended dosage of citrulline varies depending on the purpose for which you are taking it. It also depends on whether you take l-citrulline or citrulline malate, of which you need to take more to ensure adequate citrulline intake. ^[1]

For cardiovascular and sexual health support:

• Take 2 g of l-citrulline 3 times a day for a total of 6 mg per day.
• With citrulline malate, increase the dose to 3.5 g to achieve a daily intake of 10.5 g.
• You can take with food, but it is not necessary.

To support sports performance:

• Take 3.5-4.5 g of l-citrulline one hour before exercise.
• For citrulline malate, increase the dose to 6-8 g.
• On days when you don’t exercise, you can divide the same amount into smaller doses.

Dietary supplements containing citrulline

You can take citrulline in the form of l-citrulline alone or citrulline malate. You can choose between a capsule form or a soluble powder that you simply add to a shaker and mix in water, perhaps with beta-alanine, arginine and other pre-workouts.

Due to its effects, citrulline is also a key ingredient in complex pre-workouts and NO supplements such as FuePump, in which it is combined with arginine or beetroot extract for maximum muscle pump. The ingredients in these products are designed to best prepare your muscles for any upcoming athletic performance.

How does citrulline taste?

Pure l-citrulline has no specific taste. However, in the case of citrulline malate, expect it to have a slightly sour taste, reminiscent of citrus or other fruits. This is due to the malic acid or malate content.

Who can benefit most from citrulline?

Due to its effects, citrulline is suitable for athletes from various disciplines. It is suitable for strength athletes (bodybuilders, weightlifters, powerlifters), for whom it will help to manage more repetitions thanks to a better supply of nutrients and oxygen to the working muscles.

It can also be equally useful for sprinters, combat athletes, HIIT fans or cross fitters, which will then allow them to give their best intensively till every interval. Not forgetting runners, cyclists and other endurance athletes who can help delay fatigue and train longer.

Side effects of citrulline

In the event that you are healthy and take citrulline as recommended, you do not have to worry about side effects. It is a safe substance that is inherent to your body, but if you are being treated, for example, for high blood pressure or taking heart medication, you should consult your doctor about the suitability of citrulline. ^[22]

How much citrulline is too much, you may ask? It is not to be taken in excess, but the safety of citrulline has been confirmed in studies with a daily dose of up to 15 g. However, it is sufficient if you stick to the above-mentioned dosage.

What should you remember?

Citrulline is one of those supplements that are worth taking if you want to improve your athletic performance. It pumps up your muscles, which will be better supplied with oxygen and nutrients, while taking care of waste removal. This can be seen through improved performance at the gym as well as greater regeneration. It can also be beneficial for heart function, blood vessels and male sexual health. However, you should always consider your overall lifestyle and not rely on just citrulline alone.

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