Citrulline: what is it and what is it used for?

Citrullin: Was ist das und wofür wird es verwendet?

Sporting activity is the ideal opportunity to forget everyday life for a certain time and do something for your health. But in competitive sports you can quickly reach your limits. Whether in the gym or in endurance sports, there are already a number of nutritional supplements to increase performance. This includes citrulline supplements.

Citrulline promotes blood circulation and contributes to the fact that more performance can be achieved during training and the regeneration time is shortened. Would you like to know what exactly citrulline is and what effect it actually has on your body? In this article, all relevant questions about citrulline are answered in detail.

the essentials in brief

  • Citrulline, also known as L-citrulline, is an amino acid that is produced by the body itself. It is formed in the urea cycle in the liver and is therefore involved in protein breakdown. Citrulline is mainly taken as a dietary supplement in sports and promises a pump effect for more training performance and endurance.
  • By taking citrulline, the amino acid is converted into L-arginine. Nitric oxide is produced from the amino acid arginine. Nitric oxide dilates the blood vessels and thus ensures better blood flow in the body.
  • Other areas of application of citrulline is in medicine or to increase potency. The preparation can be taken either in powder form or in capsules.

Background: What you should know about citrulline

Below you will find the most important information about citrulline. All relevant wh-questions are answered here. You will then understand the role in the body, how it works, and the different uses of citrulline.

What is L-Citrulline?

Along with carbohydrates and fats, proteins are one of the main nutrients in humans. They consist of essential and non-essential amino acids. Citrulline, also known as L-citrulline, is one of the non-essential amino acids.

In contrast to the essential amino acids, these can be produced by the body itself. Citrulline is also found in natural foods, such as watermelon (1).


The highest citrulline content in food is found in the rind of watermelon. That is why the watermelon was called Citrullus lanatus. (Image source: Art Sahand Babali/Unsplash)

Citrulline is considered a pumping agent for fitness and endurance units in sports, but is not as well known as creatine, for example. Furthermore, citrulline supplements can be taken as a dietary supplement.

What role does citrulline play in the body?

To understand the role of citrulline in the body, let's focus on the liver. The urea cycle, which is responsible for protein breakdown, takes place in the liver. Urea is formed here through various chemical reactions.

Citrulline has a key role in the urea cycle.(2)

The urea is used to detoxify the metabolic toxin ammonia, which is produced during protein breakdown. In one of these reactions, citrulline is formed through the synthesis of the amino acid ornithine and carbamoyl phosphate. The resulting citrulline is synthesized in further reactions to complete the urea cycle.

Citrulline is also produced by the NO synthases. These are enzymes that are found in various cells and synthesize nitric oxide from the amino acid L-arginine. This process produces citrulline as a by-product (3).Nitric oxide is very important because it dilates blood vessels, allowing for improved blood flow.

What are the effects of taking citrulline?

However, citrulline can also be taken through supplements or food. When ingested, citrulline is converted to arginine in the kidneys. As described above, the important substance nitrogen monoxide is produced from arginine. This lowers blood pressure and promotes blood circulation (4). This effect makes citrulline an important supplement in the fields of sports, medicine and sexuality.

For sports

Taking citrulline before exercise dilates your blood vessels. The blood transports important nutrients to your muscles. With a better supply of nutrients, you can set stronger training stimuli because the energy-giving product ATP is produced longer.

Citrulline enables better nutrient supply.

You can also train longer and your regeneration is promoted (5) . The blood flow is also promoted by the vasodilatation. When ingested with citrulline, waste products such as ammonia and lactate can be broken down faster and this reduces fatigue.

In the medicine

A study in which 12 young adults were tested shows the positive effect of citrulline on cardiovascular disease. The study found that citrulline lowered diastolic and systolic blood pressure. Diastolic blood pressure measures the blood pressure in the arteries when the heart is at rest, and systolic blood pressure measures the blood pressure in the arteries when the heart is beating.

The study also shows that citrulline increases heart rate. Thus, citrulline is suitable for patients with cardiac insufficiency and may serve as a therapy for heart failure (6). Also, some scientific studies show that taking citrulline can lower blood sugar levels in diabetics (7).

To increase potency

In people with erectile dysfunction, taking citrulline separately can increase potency. The cause of impotence can be a vascular dysfunction, for example due to low nitric oxide formation.

One study showed that most impotent patients on examination had low levels of citrulline and arginine (8). The supply of citrulline or arginine supplements improves blood circulation and thus increases potency.

How do I take citrulline?

Citrulline supplements are usually available in powder or capsule form. When choosing, you should make sure that the product is free of aromas, preservatives, sweeteners, colorings and flavorings.

Citrulline is available in either capsule or powder form.

Since the effect is different for each person, the following information is only a recommendation.

You can find out the best amount for you by trying. If the preparations are in powder form, you take them with water. The optimal dosage depends on the area of ​​application.

  • For sport : a daily dose of 3 grams is recommended, for bodybuilders 3-6 grams a day. Optimally, you take citrulline about 30 minutes before training. But you can also take citrulline during and after training.
  • In medicine : To lower blood pressure, between 6 and 10 grams should be taken a day. Here you should first consult with your doctor before taking it.
  • Against impotence : 1-3 grams of citrulline are normally sufficient to increase potency. Again, I recommend that you see a doctor beforehand.

What is the difference between citrulline and citrulline malate?

Often there are citrulline products that also contain malate. Malates are a term for the salts and esters of malic acid, which gives apples their sweet and sour flavor (9).

Malate is also involved in several biochemical processes in your body, for example in energy production. The combination citrulline malate is a commonly used supplement by endurance athletes.

Woman in starting position from sprint

The dietary supplement citrulline malate is increasingly being taken by professional athletes to increase performance and improve regeneration. (Image source: Bradon Collum/unsplash)

The citrulline provides the necessary nitric oxide production. The malate optimizes the aerobic metabolism and ensures that your muscles receive enough energy to keep going even during longer training sessions.

What Are the Side Effects of Citrulline?

So far, no serious side effects of citrulline have been scientifically researched. However, some people may experience side effects. So far, mild side effects such as abdominal pain and nausea are known to users. People with certain medical conditions such as diabetes, low blood pressure or joint disorders should be a little more careful when taking it.

Gradually increasing the dosage is a good way to detect possible complications at an early stage. In addition, women who are pregnant or breastfeeding should not take citrulline. A serious illness caused by an overdose is also not known in science.

Can I stack citrulline with medications and other supplements?

In principle, caution is advised when taking citrulline with other medications. If you suffer from high blood pressure and your doctor has already prescribed you antihypertensive medication, then you should be very careful when taking citrulline. To be on the safe side, you should discuss this with your doctor in order not to achieve an increasing effect of lowering blood pressure.

The citrulline dose should also be reduced when taking medication for heart disease, so that there is no amplifying effect here either. In addition, the sexual enhancer Viagra should not be taken with citrulline. Various products can be combined to form citrulline. These include, for example, creatine, beta-alanine and L-arginine. Endurance athletes also like to take additional magnesium .

Which of the two amino acids is better, citrulline or arginine?

Now you're probably wondering why you shouldn't take arginine instead, because citrulline is converted to arginine in the body. However, citrulline is more easily absorbed by the body than arginine and has a higher bioavailability.

Compared to arginine, citrulline is not absorbed and consumed by the organs. The fact that arginine, unlike citrulline, is absorbed and used by the organs means that arginine levels are higher when citrulline is consumed than when arginine itself is consumed (9,12).

Furthermore, the side effects of arginine are known when using both preparations, while side effects only occur occasionally when taking citrulline and are therefore not that serious (10) . The possible side effects of taking arginine are a dry cough, gastrointestinal problems, loss of appetite and sleep disorders.

Accordingly, I recommend that you take citrulline as a dietary supplement. However, because taking both preparations achieves the same effect, namely the production of nitric oxide, both citrulline intake and arginine intake make sense.

What foods is citrulline found in?

Citrulline is a non-essential amino acid, so it does not have to be obtained from food. However, citrulline is also found in some foods. Citrulline is most found in watermelon. Unlike other amino acids, citrulline is not an essential component of proteins. Thus, it is not typically found in protein-rich foods.

The 5 best citrulline suppliers per 100 grams
watermelon 210-285 mg
Cucumber 20-30mg
pumpkin 10-50mg
Cantaloupe and honeydew melon 20-90 mg
zucchini 4-9 mg

The five best citrulline suppliers include watermelon, cucumber, pumpkin, cantaloupe and honeydew melon and zucchini. However, in order for citrulline to develop its active ingredient, an intake of at least 1000 mg citrulline is required, depending on the area of ​​application. So if you want to take citrulline for sports, for example, you have to resort to dietary supplements.

When is supplementation with additional L-citrulline useful?

A supplementation with additional citrulline is particularly useful for increasing performance in endurance and strength sports and is also used there the most. Citrulline is most beneficial when taken before a workout.

By increasing and assisting in nitric oxide production and the associated good supply of nutrients to the muscles, it influences your training performance and endurance. In addition, muscle soreness is prevented by taking it and thus regeneration is accelerated.

Citrulline Capsules

In addition to citrulline consumption, a balanced and macronutrient-rich diet is essential for optimal results in sports. (Image source: Sharon McCutcheon/

In a study, the effect of citrulline malate was tested on 23 handball players who did intensive training 4 times a week for 4 weeks. 12 of them were given 1g citrulline malate in the morning, at noon and in the evening.

The remaining 11 handball players received a placebo product. After the training sessions, the handball players who received citrulline malate had a 60.7% lower blood lactate value. This suggests that taking citrulline effectively promotes recovery and increases performance (11).

Especially in the bodybuilding sector, citrulline is best known. However, in order to achieve optimal values, the general nutrient requirement must of course not be ignored. Only with a sufficient amount of nutrients for muscle building can endurance or strength training also lead to more muscle mass.

For the medical field, the use of citrulline should be consumed with caution, because there are many studies whose results are not yet mature and sometimes contradict each other. Nevertheless, citrulline can increase potency and lower blood pressure. For the medical field, I recommend that you see a doctor first, because there are many medications and supplements whose effects are irreversibly verifiable.


Now you have received a large overview of the topic of citrulline. Due to the versatile effects of citrulline, taking it as a dietary supplement is highly recommended.

In addition, science has so far not found any major side effects when taking citrulline. If you want more energy during your workouts and faster regeneration, I recommend the combination of citrulline and malate as a dietary supplement.

Many professional athletes also rely on the supplement and report a positive effect. Before you want to take citrulline to lower blood pressure or increase potency, you should consult your doctor. Otherwise, you can try it out and see which dosage achieves the best effect for you.

Individual proofs(12)

  1. Rimando, AM, Perkins-Veazie, PM (2005). University, MS 38677, USA. Journal of Chromatography A. Determination of citrulline in watermelon cattle. Source
  2. Sewell, AC "Citrulline." Lexicon of medical laboratory diagnostics. Springer, Berlin, Heidelberg, 2019. 593-594. Source
  3. Figueroa A, Trivino JA, Sanchez-Gonzalez MA, Vicil F. Oral L-citrulline supplementation attenuates blood pressure response to cold pressor test in young men. Am J Hypertense. 2010 Jan;23(1):12-6. doi: 10.1038/ajh.2009.195. Epub 2009 Oct 22. PMID: 19851298. Source
  4. Figueroa A, Wong A, Jaime SJ, Gonzales JU. Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance. Curr Opin Clin Nutr Metab Care. 2017 Jan;20(1):92-98. doi: 10.1097/MCO.0000000000000340 Transfer title to Citavi project based on this DOI. PMID: 27749691 Transfer title to Citavi project using this Pubmed ID. Source
  5. Alsop P, Hauton D. Oral nitrate and citrulline decrease blood pressure and increase vascular conductance in young adults: a potential therapy for heart failure. Eur J Appl Physiol. 2016 Sep;116(9):1651-61. doi: 10.1007/s00421-016-3418-7 Transfer title to Citavi project based on this DOI. Epub 2016 Jun 22. PMID: 27333912 Transfer title to Citavi project using this Pubmed ID; PMCID: PMC4983290. Transfer title to Citavi project based on this PMC ID Source
  6. Barassi A, Corsi Romanelli MM, Pezzilli R, Damele CA, Vaccalluzzo L, Goi G, Papini N, Colpi GM, Massaccesi L, Melzi d'Eril GV. Levels of l-arginine and l-citrulline in patients with erectile dysfunction of different etiology. Andrology. 2017 Mar;5(2):256-261. doi: 10.1111/andr.12293. Epub 2017 Feb 8. PMID: 28178400. Source
  7. Azizi S, Mahdavi R, Vaghef- Mehrabany E, Maleki V, Karamzad N, Ebrahimi-Mameghani M. Potential roles of citrulline and watermelon extract on metabolic and inflammatory variables in diabetes mellitus, current evidence and future directions: A systematic review. Clin Exp Pharmacol Physiol. 2020 Feb;47(2):187-198. doi: 10.1111/1440-1681.13190. Epub 2019 Nov 17. PMID: 31612510. Source
  8. Hartmann-Schreier J, Malate, RD-13-00318 (2003) in Böckler F, Dill B, Dingerdissen U, Eisenbrand G, Faupel F, Fugmann B, Gamse T, Matissek R, Pohnert G ., Sprenger G., RÖMPP [Online], Stuttgart, Georg Thieme Verlag, [February 2021] Source
  9. Papadia C, Osowska S, Cynober L, Forbes A. Citrullines in health and disease. Review on human studies. Clin Nutr. 2018 Dec;37(6pt A):1823-1828. doi: 10.1016/j.clnu.2017.10.009. Epub 2017 Oct 16. PMID: 29107336. Source
  10. TY-JOUR AU - Botchlett, Rachel AU - Lawler, John AU - Wu, Guoyao PY - 2013/08/01 SP-439 EP-446 T1 - L-Arginine and L-Citrulline in Sports Nutrition and Health DO - 10.1016/B978-0-12-396454-0.00045-X JO - Nutrition and Enhanced Sports Performance: Muscle Building, Endurance, and Strength HE - Source
  11. Kiyici F, Eroğlu H, Kishali NF, Burmaoglu G. The Effect of Citrulline/Malate on Blood Lactate Levels in Intensive Exercise. Biochem Genet. 2017 Dec;55(5-6):387-394. doi: 10.1007/s10528-017-9807-8. Epub 2017 Jun 29. PMID: 28664349. Source
  12. Bahri S, Zerrouk N, Aussel C, Moinard C, Crenn P, Curis E, Chaumeil JC, Cynober L, Sfar S. Citrullines: from metabolism to therapeutic use. Nutrition. 2013 Mar;29(3):479-84. doi: 10.1016/j.nut.2012.07.002. Epub 2012 Sep 28. PMID: 23022123. Source
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