Last updated: August 30, 2021

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Many of us dread the passage of time. While no one has yet to escape aging, the new challenges of growing older can cause distress in even the most rational individuals. This is why it isn't surprising that the supplementation industry is researching every possible remedy for the problems arising from this natural phenomenon.

Citrulline is a rare amino acid in our diet. When consumed in sufficient quantities, however, it may support normal cardiovascular health thanks to its antioxidant properties. This effect can potentially extend to the whole body and could improve sexual performance in both men and women. Are you ready to learn more about it?




Key Facts

  • Citrulline is an amino acid rarely found in our diet, except for watermelon.
  • Its consumption promotes blood flow and could improve sexual performance, increase muscle growth, and serve as a nutritional supplement in individuals with low levels of amino acids.
  • There are various factors to evaluate before purchasing a citrulline supplement. These include the presence of potential allergens, the product type, or the compatibility with a vegan diet, among others.

Our Selection: The Best Citrulline Supplements

We know just how difficult it can be to find the right supplement for your needs, which is why we have selected some of the best citrulline products currently available out there. Each of them stands out for its overall quality and value for money. We have included a description for all of them, so you can make an informed decision and reap all the benefits of citrulline.

Shopping Guide: Everything You Should Know About Citrulline

Citrulline is an amino acid capable of increasing arginine levels in your blood. This property will help lower blood pressure and improve blood perfusion in the muscles of older adults, promoting sports performance. Its most highly valued effect, however, is its role in the treatment of erectile dysfunction.

Watermelon pulp and skin are rich in citrulline.
(Source: Melpomen: 121481829/ 123rf.com)

What is citrulline exactly?

Citrulline is an amino acid, one of the building blocks your body uses to maintain a healthy balance. It plays a major role in forming new muscle proteins and replenishing the reserves of another amino acid, arginine.

Most foods of animal and plant origin provide tiny amounts of citrulline.

However, our organism can synthesize it from other amino acids – such as glutamine – without needing to ingest it directly. This characteristic makes citrulline a non-essential amino acid (1).

The intestine absorbs it efficiently, which means that it can cross the body's natural barriers easily to reach the bloodstream. The kidneys then metabolize it, transforming it into arginine. In the liver, citrulline will become part of the urea cycle, a chemical process that allows your body to eliminate toxins and potentially harmful substances.

Discovered in the 1930s, this amino acid is particularly attractive for its role as a pharmaconutrient, being able to be transformed into other compounds that are vital to the body. As a dietary supplement, it may be very beneficial for ill or convalescent people (2).

Did you know that watermelon skin is very rich in citrulline? Don't throw it away! It's perfectly edible and can be added to milkshakes and smoothies.

What is the purpose of citrulline?

Its primary function is to increase levels of arginine, an essential amino acid capable of preserving arterial and muscle health. In fact, citrulline consumption may be more effective than arginine intake to raise blood levels of the latter molecule.

Citrulline may be a powerful protector of the endothelium, the tissue that forms the blood vessels. In that regard, it increases the levels of vasodilatory substances, such as nitric oxide, and prevents the immune system from acting indiscriminately on the vessel tissue. This, in turn, contributes to combating premature aging of your arteries and veins.

In addition, studies have shown that citrulline had an anabolic potential by stimulating muscle blood flow and activating a chain of signaling molecules that regulate the growth of muscle fibers. In the table below, you can learn more about the different actions of this amino acid (2, 3):

System Function of citrulline Consequence
Musculoskeletal Activation of muscle synthesis.

Increase of the muscular blood flow.

Muscular growth.

Prevention of catabolism (muscle breakdown).

Hepatic Urea metabolism Elimination of excess ammonia in the blood
Cardiovascular Arginine synthesis.

Synthesis of nitric oxide (through arginine).

Vasodilation.

Decrease in arterial stiffness.

Reduction of blood pressure.

Prevention of myocardial damage.

Prevention of endothelial dysfunction.

Immune Decrease in the number of circulating white blood cells Protection against endothelial damage mediated by white blood cells
Metabolism Muscle vasodilation in response to increased glucose.

Increased cellular activity.

Increased lipolysis (destruction of fat cells).

Decreased insulin resistance.

Increased energy synthesis.

Reduction of body weight.

Please keep in mind that this amino acid is still undergoing many investigations. Most of the findings presented above are the result of testing on animals (mice) or small groups of humans. While its beneficial role in cardiometabolic health has been proven (3), more studies are required to validate the incredible potential of this substance.

What foods are rich in citrulline?

As we explained earlier, this amino acid is difficult to obtain through a normal diet, with negligible amounts found in meat, fish, and vegetables. Watermelon is the only substantial source of citrulline, so it is certainly recommended if you're looking to increase your levels (2).

The content in the watermelon will depend on characteristics such as skin color, thickness of the rind, and the presence or absence of seeds, among others. It is estimated that the yellow watermelon is the richest in citrulline (around 36 milligrams per 100 grams) and that the common red watermelon has the lowest content (16 mg per 100 g) (4).

You should know that most of the effects of citrulline observed were obtained after supplementation with doses ranging from 3 to 5 grams (3,000-5,000 mg) (2). While the consumption of watermelon can add small amounts to your diet, reproducing the effects witnessed in clinical trials is challenging.

However, it is possible to extract the citrulline directly from the watermelon's skin. The dehydrated powder is then used to create natural supplements that provide this amino acid in a concentrated and convenient form. That way, you won't need to eat large quantities of watermelon, which could also be costly in the long run.

Citrulline may contribute to increasing your muscle mass.
(Source: Koval: 43123416/ 123rf.com)

What types of citrulline supplements are there?

If you're determined to use a citrulline supplement to raise your levels simply and effectively, you have various products at your disposal. We can categorize them in two main types – pure citrulline and citrulline malate.

  • Citrulline or L-citrulline: This is the name under which the active form of the amino acid is marketed, without any additional molecules.
  • Citrulline malate: The amino acid is combined with malic acid (malate), a compound found in nature and that was first isolated in apple cider. It is very present in the chemical reactions necessary to produce energy (ATP).

In that regard, citrulline malate supplements may provide the benefits of citrulline with an additional energy boost that can come in very handy for athletes and anyone looking to gather their strength during the day (5, 6). If you don't need to raise your energy levels, L-citrulline supplements are more affordable.

In addition, you can purchase supplements that blend citrulline with other L-citrulline function-enhancing molecules. These include the amino acids arginine and ornithine, which are part of the cycles of protein synthesis and waste disposal along with citrulline.

  • Citrulline + arginine: The combination of arginine and its precursor, citrulline, will produce a remarkable rise in the levels of the former. As you now know, higher arginine levels enhance the creation of the vasodilator nitric oxide, which may lower blood pressure, increase muscle blood flow, and regulate the immune function (7, 8).
  • Citrulline + ornithine: Ornithine is an amino acid linked to the metabolism of both citrulline and arginine. It may improve the response to stress, thus reducing the feeling of fatigue (9). While no reliable studies have been conducted on the actual effectiveness of this blend, it is marketed to the public as a supplement that speeds up muscle recovery.

Citrulline may improve sexual performance.
(Source: Shidlovski: 92909879/ 123rf.com)

What are the benefits of citrulline supplementation?

This amino acid offers a wide range of uses and benefits. In addition to improving the sexual health of men and women, this nutritional supplement will promote cardiovascular health, regulate your immune function, and exert an overall antioxidant effect on your organism. Here is a list of its main actions (2, 3, 15):

    • Cardiovascular health: Citrulline may attenuate the increase in blood pressure that occurs during stressful or physically demanding situations. This would be particularly beneficial for individuals diagnosed with prehypertension (above-normal blood pressure, but too low to need medication).
    • Muscle growth: Citrulline generates an increase in muscle blood flow and stimulates muscle protein synthesis, favoring an increase in lean mass.
    • Sports performance: Enhanced blood flow leads to a discreet-yet-significant increase in sports performance in older adults. In addition, it promotes post-training recovery. Note that young and healthy people cannot benefit from this phenomenon.
    • Nutrition: Studies have demonstrated that our organism is very tolerant to this amino acid and can absorb it well. This can be useful for convalescent individuals who require additional nutrition to improve their blood protein levels.

Many people wonder whether or not citrulline supplements may contribute to weight loss. In reality, this amino acid increases lean mass and could even promote greater bone density, which would lead to paradoxical weight gain. That being said, this would not alter your physical appearance.

Your body metabolizes citrulline to produce arginine.
(Source: Sonyakamoz: 81976369/ 123rf.com)

Are citrulline or arginine supplements better?

You can learn more about the benefits of arginine in another shopping guide; closely related to citrulline, this amino acid can promote muscle growth, strengthen immunity, and help maintain healthy cardiovascular function. Its effects and those of citrulline are very similar, which is why many of us wonder which one is more efficient.

Both supplements are able to increase the concentrations of the vasodilator nitric oxide in your body, potentially leading to a lowering of the blood pressure. However, these products have significant differences, as you can see in the following table (18, 19, 20):

Arginine Citrulline
Effects Tissue renewal.

Increase of muscle mass.

Reduction of blood pressure.

Increase of muscular perfusion.

Improvement of sexual health.

Activation of the immunity.

Increase of the levels of arginine and its benefits.

Improvement of the nutritional status.

Increase of muscle mass.

Reduction of blood pressure.

Improvement of sexual health.

Regulation of immunity.

Absorption Good Better
Side effects Gastrointestinal intolerance.

Arterial hypotension.

Recurrent cold sores.

None
Interactions Antidiabetics.

Antihypertensive drugs.

Antidiabetics.

Antihypertensive drugs.

Nitrates.

Long-term safety Up to 3 years Up to 6 months

Studies in rats seem to confirm the activity of citrulline in increasing muscle mass and sports performance. In addition, these supplements may be better absorbed by the organism, and their intake would not cause gastrointestinal discomfort (the main side effect of arginine supplements).

The big remaining question regarding citrulline is its long-term safety. While arginine appears to be safe for long periods (up to 3 years in humans), the amino acid citrulline needs further study before it can be recommended for supplementation for more than six months at a time.

Is citrulline supplementation safe?

Supplementing with this amino acid for a limited time – one to six months – seems to be safe in healthy adults. Its properties would particularly benefit older people with vascular conditions, and it has not proven to be useful in people under the age of 50 (2).

While there have been no reports of relevant drug interactions, the effect of this supplement on blood pressure and metabolism could impact the effect of antidiabetics, antihypertensives, and nitrates (such as drugs for angina pectoris or erectile dysfunction). If you are treated with any of these, you are strongly advised to seek medical guidance before supplementing.

In a similar vein, the use of citrulline without medical supervision is not recommended for pregnant or breastfeeding women. These supplements should not be used freely by minors under the age of 18, by individuals with chronic diseases, or by people undergoing surgery.

Did you know that citrulline was first isolated from watermelon extract? The word itself comes from the Latin name for this fruit, Citrullus.

Buyer's Guide

As you noticed in our selection of products earlier, there is a wide range of citrulline supplements available on the market. If you're wondering how to pick the right one for your needs, the section below is what you need. We have detailed the main shopping criteria to take into account before you make your purchase.

Allergies & Intolerances

Watermelon allergy is a rare food intolerance. However, most citrulline supplements consist of the extract of this fruit, which is why you should avoid them if you suffer from this type of allergy. If you are intolerant to gluten, lactose, or nuts, on the other hand, carefully check the list of excipients before use.

Citrulline supplements are also marketed under the name L-citrulline.
(Source: Pustynnikova: 77497902/ 123rf.com)

Vegan or Vegetarian Diet

Citrulline is of plant origin, so you will find many vegan-friendly supplements out there. However, make sure that the capsule and excipients are free of animal products before you buy any product. You will want to avoid supplements that contain lactose and gelatin as part of their composition.

Dosage Form

Citrulline products come in capsule and powder form. The former provides a comfortable and fast supplementation, being particularly handy for individuals needing low doses of the amino acid. Powder preparations allow you to personalize the amount of citrulline you consume each day, adapting to your own needs.

Citrulline may be an effective alternative to Viagra® in men with mild erectile dysfunction who do not want drug treatment.
(Source: Epicstockmedia: 31332528/ 123rf.com)

Summary

Citrulline is an amino acid with incredible potential. Its effects on cardiovascular health and muscle performance could improve the quality of life of older adults, allowing them to enjoy a fuller life both at the athletic and intimate levels. Indeed, it stands as an alternative to manage erectile dysfunction.

If you need to boost your cardiovascular and muscle health, citrulline may be able to support you during the more intense periods. This natural substance could enhance your recovery process or your libido. Who knew that watermelon could be so miraculous?

We hope you enjoyed our guide on citrulline. Don't forget to share it on your social media and leave us a comment in the section below!

(Source of featured image: Lightfieldstudios: 86092432/ 123rf.com)

References (20)

1. McNeal CJ, Meininger CJ, Reddy D, Wilborn CD, Wu G. Safety and Effectiveness of Arginine in Adults. J Nutr [Internet]. 2016 Dec 1 [cited 2019 Oct 23];146(12):2587S-2593S.
Source

2. Agarwal U, Didelija IC, Yuan Y, Wang X, Marini JC. Supplemental Citrulline Is More Efficient Than Arginine in Increasing Systemic Arginine Availability in Mice. J Nutr [Internet]. 2017 Apr [cited 2019 Oct 23];147(4):596–602.
Source

3. Mohan S, Wu C-C, Shin S, Fung H-L. Continuous exposure to l-arginine induces oxidative stress and physiological tolerance in cultured human endothelial cells. Amino Acids [Internet]. 2012 Sep 1 [cited 2019 Oct 23];43(3):1179–88.
Source

4. Sureda A, Córdova A, Ferrer MD, Pérez G, Tur JA, Pons A. L-Citrulline-malate influence over branched chain amino acid utilization during exercise. Eur J Appl Physiol [Internet]. 2010 Sep [cited 2019 Oct 23];110(2):341–51.
Source

5. Gonzales JU, Raymond A, Ashley J, Kim Y. Does citrulline supplementation improve exercise blood flow in older adults? Exp Physiol [Internet]. 2017 Dec 1 [cited 2019 Oct 23];102(12):1661–71.
Source

6. Barkhidarian B, Khorshidi M, Shab-Bidar S, Hashemi B. Effects of L-citrulline supplementation on blood pressure: A systematic review and meta-analysis. Avicenna J phytomedicine [Internet]. 2019 [cited 2019 Oct 23];9(1):10–20.
Source

7. Bottari A, Belcaro G, Ledda A, Luzzi R, Cesarone MR, Dugall M. Lady Prelox® improves sexual function in generally healthy women of reproductive age. Minerva Ginecol [Internet]. 2013 Aug [cited 2019 Oct 23];65(4):435–44.
Source

8. Shirai M, Hiramatsu I, Aoki Y, Shimoyama H, Mizuno T, Nozaki T, et al. Oral L-citrulline and Transresveratrol Supplementation Improves Erectile Function in Men With Phosphodiesterase 5 Inhibitors: A Randomized, Double-Blind, Placebo-Controlled Crossover Pilot Study. Sex Med [Internet]. 2018 Dec 1 [cited 2019 Oct 23];6(4):291–6.
Source

9. Cormio L, De Siati M, Lorusso F, Selvaggio O, Mirabella L, Sanguedolce F, et al. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology [Internet]. 2011 Jan [cited 2019 Oct 20];77(1):119–22.
Source

10. Davies KP. Development and therapeutic applications of nitric oxide releasing materials to treat erectile dysfunction. Futur Sci OA [Internet]. 2015 Aug 1 [cited 2019 Oct 23];1(1):fso.15.53.
Source

11. Hotta Y, Shiota A, Kataoka T, Motonari M, Maeda Y, Morita M, et al. Oral L-citrulline supplementation improves erectile function and penile structure in castrated rats. Int J Urol [Internet]. 2014 Jun [cited 2019 Oct 23];21(6):608–12.
Source

12. Miyake M, Kirisako T, Kokubo T, Miura Y, Morishita K, Okamura H, et al. Randomised controlled trial of the effects of L-ornithine on stress markers and sleep quality in healthy workers. Nutr J [Internet]. 2014 Dec 3 [cited 2019 Oct 22];13(1):53.
Source

13. Morita M, Hayashi T, Ochiai M, Maeda M, Yamaguchi T, Ina K, et al. Oral supplementation with a combination of l-citrulline and l-arginine rapidly increases plasma l-arginine concentration and enhances NO bioavailability. Biochem Biophys Res Commun [Internet]. 2014 Nov 7 [cited 2019 Oct 22];454(1):53–7.
Source

14. McRae MP. Therapeutic Benefits of l-Arginine: An Umbrella Review of Meta-analyses. J Chiropr Med [Internet]. 2016 Sep [cited 2019 Oct 22];15(3):184–9.
Source

15. Glenn JM, Gray M, Jensen A, Stone MS, Vincenzo JL. Acute citrulline-malate supplementation improves maximal strength and anaerobic power in female, masters athletes tennis players. Eur J Sport Sci [Internet]. 2016 Nov 16 [cited 2019 Oct 22];16(8):1095–103.
Source

16. Pérez-Guisado J, Jakeman PM. Citrulline Malate Enhances Athletic Anaerobic Performance and Relieves Muscle Soreness. J Strength Cond Res [Internet]. 2010 May [cited 2019 Oct 22];24(5):1215–22.
Source

17. Rimando AM, Perkins-Veazie PM. Determination of citrulline in watermelon rind. J Chromatogr A [Internet]. 2005 Jun 17 [cited 2019 Oct 21];1078(1–2):196–200.
Source

18. Allerton TD, Proctor DN, Stephens JM, Dugas TR, Spielmann G, Irving BA. L-citrulline supplementation: Impact on cardiometabolic health. Vol. 10, Nutrients. MDPI AG; 2018.
Source

19. Papadia C, Osowska S, Cynober L, Forbes A. Citrulline in health and disease. Review on human studies. Clin Nutr [Internet]. 2018 Dec [cited 2019 Oct 20];37(6):1823–8.
Source

20. H. Stipanuk M, A. Caudill M. Biochemical, physiological, and molecular aspects of human nutrition. 3rd edition. Elsevier; 2013. 948 p.
Source

Why you can trust me?

Scientific article
McNeal CJ, Meininger CJ, Reddy D, Wilborn CD, Wu G. Safety and Effectiveness of Arginine in Adults. J Nutr [Internet]. 2016 Dec 1 [cited 2019 Oct 23];146(12):2587S-2593S.
Go to source
Scientific article
Agarwal U, Didelija IC, Yuan Y, Wang X, Marini JC. Supplemental Citrulline Is More Efficient Than Arginine in Increasing Systemic Arginine Availability in Mice. J Nutr [Internet]. 2017 Apr [cited 2019 Oct 23];147(4):596–602.
Go to source
Scientific article
Mohan S, Wu C-C, Shin S, Fung H-L. Continuous exposure to l-arginine induces oxidative stress and physiological tolerance in cultured human endothelial cells. Amino Acids [Internet]. 2012 Sep 1 [cited 2019 Oct 23];43(3):1179–88.
Go to source
Clinical study
Sureda A, Córdova A, Ferrer MD, Pérez G, Tur JA, Pons A. L-Citrulline-malate influence over branched chain amino acid utilization during exercise. Eur J Appl Physiol [Internet]. 2010 Sep [cited 2019 Oct 23];110(2):341–51.
Go to source
Clinical study
Gonzales JU, Raymond A, Ashley J, Kim Y. Does citrulline supplementation improve exercise blood flow in older adults? Exp Physiol [Internet]. 2017 Dec 1 [cited 2019 Oct 23];102(12):1661–71.
Go to source
Systematic review
Barkhidarian B, Khorshidi M, Shab-Bidar S, Hashemi B. Effects of L-citrulline supplementation on blood pressure: A systematic review and meta-analysis. Avicenna J phytomedicine [Internet]. 2019 [cited 2019 Oct 23];9(1):10–20.
Go to source
Clinical study
Bottari A, Belcaro G, Ledda A, Luzzi R, Cesarone MR, Dugall M. Lady Prelox® improves sexual function in generally healthy women of reproductive age. Minerva Ginecol [Internet]. 2013 Aug [cited 2019 Oct 23];65(4):435–44.
Go to source
Clinical study
Shirai M, Hiramatsu I, Aoki Y, Shimoyama H, Mizuno T, Nozaki T, et al. Oral L-citrulline and Transresveratrol Supplementation Improves Erectile Function in Men With Phosphodiesterase 5 Inhibitors: A Randomized, Double-Blind, Placebo-Controlled Crossover Pilot Study. Sex Med [Internet]. 2018 Dec 1 [cited 2019 Oct 23];6(4):291–6.
Go to source
Clinical study
Cormio L, De Siati M, Lorusso F, Selvaggio O, Mirabella L, Sanguedolce F, et al. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology [Internet]. 2011 Jan [cited 2019 Oct 20];77(1):119–22.
Go to source
Review article
Davies KP. Development and therapeutic applications of nitric oxide releasing materials to treat erectile dysfunction. Futur Sci OA [Internet]. 2015 Aug 1 [cited 2019 Oct 23];1(1):fso.15.53.
Go to source
Clinical study
Hotta Y, Shiota A, Kataoka T, Motonari M, Maeda Y, Morita M, et al. Oral L-citrulline supplementation improves erectile function and penile structure in castrated rats. Int J Urol [Internet]. 2014 Jun [cited 2019 Oct 23];21(6):608–12.
Go to source
Scientific article
Miyake M, Kirisako T, Kokubo T, Miura Y, Morishita K, Okamura H, et al. Randomised controlled trial of the effects of L-ornithine on stress markers and sleep quality in healthy workers. Nutr J [Internet]. 2014 Dec 3 [cited 2019 Oct 22];13(1):53.
Go to source
Scientific article
Morita M, Hayashi T, Ochiai M, Maeda M, Yamaguchi T, Ina K, et al. Oral supplementation with a combination of l-citrulline and l-arginine rapidly increases plasma l-arginine concentration and enhances NO bioavailability. Biochem Biophys Res Commun [Internet]. 2014 Nov 7 [cited 2019 Oct 22];454(1):53–7.
Go to source
Meta analysis
McRae MP. Therapeutic Benefits of l-Arginine: An Umbrella Review of Meta-analyses. J Chiropr Med [Internet]. 2016 Sep [cited 2019 Oct 22];15(3):184–9.
Go to source
Scientific article
Glenn JM, Gray M, Jensen A, Stone MS, Vincenzo JL. Acute citrulline-malate supplementation improves maximal strength and anaerobic power in female, masters athletes tennis players. Eur J Sport Sci [Internet]. 2016 Nov 16 [cited 2019 Oct 22];16(8):1095–103.
Go to source
Scientific article
Pérez-Guisado J, Jakeman PM. Citrulline Malate Enhances Athletic Anaerobic Performance and Relieves Muscle Soreness. J Strength Cond Res [Internet]. 2010 May [cited 2019 Oct 22];24(5):1215–22.
Go to source
Scientific study
Rimando AM, Perkins-Veazie PM. Determination of citrulline in watermelon rind. J Chromatogr A [Internet]. 2005 Jun 17 [cited 2019 Oct 21];1078(1–2):196–200.
Go to source
Review article
Allerton TD, Proctor DN, Stephens JM, Dugas TR, Spielmann G, Irving BA. L-citrulline supplementation: Impact on cardiometabolic health. Vol. 10, Nutrients. MDPI AG; 2018.
Go to source
Review article
Papadia C, Osowska S, Cynober L, Forbes A. Citrulline in health and disease. Review on human studies. Clin Nutr [Internet]. 2018 Dec [cited 2019 Oct 20];37(6):1823–8.
Go to source
Academic book
H. Stipanuk M, A. Caudill M. Biochemical, physiological, and molecular aspects of human nutrition. 3rd edition. Elsevier; 2013. 948 p.
Go to source
Reviews