Citrulline is gaining increasing popularity as a supplement that may increase blood flow, with some studies suggesting that it might help with power output and endurance during workouts. This non-essential amino acid is produced in the body and it’s found in nature in legumes, organ meat, and especially watermelon — the name “citrulline” is actually derived from the Latin word for watermelon — and there are dozens of different supplements on the market including powders, pills, and citrulline malate, a form that might be more useful for improving energy production.
We’ve taken a look at everything on offer to land on the best for your needs.
Editor’s Pick
KAGED MUSCLE Citrulline
KAGED MUSCLE is known for using fermented amino acids in their products — most competitors obtain amino acids from animal sources, so KAGED MUSCLE’s citrulline is vegan friendly. In addition, it’s been third party tested by Informed Choice, a well known organization that screens for banned substances and impurities. It’s also gluten free, non-GMO, and certified kosher.
Pros
- This citrulline is third party tested by the well regarded organization Informed Choice.
- This is one of the rare citrullines that is vegan friendly.
- The product is gluten free, non-GMO, and kosher.
Cons
- Many consumers report that while it’s tasteless, this citrulline has an unpleasant smell.
Third party tested, non-GMO, gluten free, and even vegan friendly, this is the crème de la crème of citrulline supplements.
Also Consider
Doctor’s Best L-Citrulline
Inexpensive and one of the few vegan-friendly citrulline supplements, Doctor’s Best has put together a solid product that ticks a lot of boxes: it’s non-GMO, soy-free, gluten-free, made in a cGMP facility, and perhaps most importantly it’s third party tested.
Pros
- This citrulline is vegan friendly.
- The product is third party tested to ensure label accuracy and purity.
Cons
- There are some reports that the bottle can come unsealed during shipping.
A well priced citrulline that's vegan friendly and has been third party tested for purity.
Best Value
Bulk Supplements Citrulline
As the name suggests, one can buy Bulk Supplements in bags as large as 25 kilograms, but whatever the size of the package (they come as low as 100 grams), it’s always terrific value. The no frills citrulline has no added ingredients and the final product is tested in house for purity.
Pros
- Bulk Supplements is extraordinarily inexpensive.
- The product is made in an allergen free, Good Manufacturing Practices-certified facility.
- It’s written that the citrulline is “lab tested for verification and guaranteed purity,” though it’s unclear if this means third party tested.
Cons
- Bulk Supplements doesn’t include a serving spoon in their bags.
- Oftentimes, the bag doesn’t reseal.
Far and away the most inexpensive citrulline supplement on the market, plus it's tested for purity and free from major allergens.
Best Pills
Nutricost L-Citrulline
Nutricost produces a lot of inexpensive supplements and their citrulline pills hit a nice sweet spot between quality and value. The citrulline is non-GMO, it’s gluten free, it’s made in an FDA-registered facility, and it’s third party tested to ensure purity and label accuracy.
Pros
- On a per gram basis, this is a pretty inexpensive citrulline product, particularly given the fact that it comes in capsules.
- This form of citrulline is easy to consume on the go.
- Nutricost’s citrulline is third party tested for purity and label accuracy.
Cons
- The capsules are made from gelatin, so they’re not vegetarian friendly.
- The capsules also contain magnesium stearate and stearic acid, which help keep the powder from sticking to the machinery in the facility in which it’s made — some consider these “fillers” undesirable.
Non-GMO, gluten free, made in an FDA-registered facility, and third party tested, these are the best citrulline pills on the market.
Best Citrulline Malate
Hard Rhino L-Citrulline DL-Malate
Citrulline malate has citrulline combined with malic acid, which is often included in supplements as a preservative but it may also help with stamina. Hard Rhino’s offering is great value, free from major allergens, and tested with Thermo Spectrum analysis to ensure purity and label accuracy.
Pros
- This citrulline malate is reasonably priced.
- The product is made in the United States at an FDA registered facility.
- It’s guaranteed to be free from major allergens.
Cons
- It’s been tested for purity and banned substances, but the testing was done in-house, not by a third party.
Lab tested for purity and label accuracy, Hard Rhino's citrulline malate is terrific value and free from major allergens.
What Are the Benefits of Citrulline?
Citrulline is an amino acid that appears to increase plasma levels of arginine and ornithine, improving nitric oxide metabolism.(1)(2)(3) Nitric oxide seems to play a big role in relaxing blood vessels, which has implications for circulatory health and blood flow, and some studies have even linked it to improved erection hardness, making citrulline a somewhat popular supplement for erectile dysfunction.(4)(5)
For athletes, an increase in nitric oxide production might improve both anaerobic training (like sprinting) and aerobic (endurance-based) workouts, in addition to potentially reducing the amount of oxygen needed for exertion.(6)(7)(8)(9)(10) Citrulline itself has been seen in a few studies to improve power output and time to fatigue in cyclists and tennis players.(11)(12)
As for dosing, research in the International Journal of Cardiology and the European Journal of Applied Physiology found that a dose of 5 or so grams of citrulline may increase nitric oxide production and blood flow. (13)(14)
Citrulline vs Citrulline Malate
Citrulline is the pure amino acid, while citrulline malate is an organic compound that occurs naturally in many fruits. It’s citrulline combined with malic acid, which contributes to the sour taste of fruits — it’s abundant in apples and is often used as a flavoring in supplements. While citrulline does have links with improved performance, citrulline malate may also help to provide more energy for high intensity exercise because of its potential role in converting food into usable energy because of its role in in the Krebs cycle.
That’s the theory, anyway. Evidence is a little mixed; there is evidence, like a study published in 2010, that found citrulline malate to be useful at improving the number of repetitions in a training session and improve recovery, and another found it to postpone exercise fatigue in handball players.(15)(16) Other studies have found no effect on performance or muscle soreness.(17)(18)
At this time, we don’t have good research comparing the two supplements against one another and the additional benefits of adding malate aren’t concrete, but it’s a promising supplement nonetheless.
BarBend Tips
- Be mindful of the dosage of citrulline. Many supplements will include one or two grams, but research suggests five to eight grams is ideal for the benefits.
- It’s possible that loading citrulline over time may be an ideal way to accrue the potential benefits. Some users take a few grams every day for a week before expecting results. At the moment, there’s not quite enough evidence to suggest either acute or chronic dosing is superior.
- If natural sources of citrulline are preferred, watermelon is widely considered the best source, though the exact amount present in a serving is unclear. Some estimate that there is about 0.25 to 0.5 grams of citrulline per cup of watermelon flesh; it’s most concentrated in the white rind surrounding the flesh.
- Side effects aren’t widely reported from citrulline supplementation. A very small minority experience upset stomachs or heartburn, so it may be prudent to start with a small dosage and gradually increase.
Wrapping Up
Citrulline is generally considered safe and today it’s one of the most popular ingredients in pre workouts. But always remember, especially if the intention is to take citrulline to improve circulatory health or erectile dysfunction, that it’s important to speak with a physician before starting a new supplement regimen.
References
1. Flam BR, et al. Endothelial nitric oxide production is tightly coupled to the citrulline-NO cycle. Nitric Oxide. 2007 Nov-Dec;17(3-4):115-21.
2. Sureda A, et al. Effects of L-citrulline oral supplementation on polymorphonuclear neutrophils oxidative burst and nitric oxide production after exercise. Free Radic Res. 2009 Sep;43(9):828-35.
3. Nakata M, et al. Endocrinology: nitric oxide-mediated insulin secretion in response to citrulline in islet beta-cells. Pancreas. 2003 Oct;27(3):209-13.
4. Moncada S, et al. The discovery of nitric oxide as the endogenous nitrovasodilator. Hypertension. 1988 Oct;12(4):365-72.
5. Cormio L, et al. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology. 2011 Jan;77(1):119-22.
6. Wylie LJ, et al. Dietary nitrate supplementation improves team sport-specific intense intermittent exercise performance. Eur J Appl Physiol. 2013 Jul;113(7):1673-84.
7. Lansley KE, et al. Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. J Appl Physiol (1985). 2011 Mar;110(3):591-600.
8. Kelly J, et al. Effects of short-term dietary nitrate supplementation on blood pressure, O2 uptake kinetics, and muscle and cognitive function in older adults. Am J Physiol Regul Integr Comp Physiol. 2013 Jan 15;304(2):R73-83.
9. Murphy M, et al. Whole beetroot consumption acutely improves running performance. J Acad Nutr Diet. 2012 Apr;112(4):548-52.
10. Lansley KE, et al. Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. J Appl Physiol (1985). 2011 Mar;110(3):591-600.
11. Suzuki, T. et al. (2016) Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men: Double-blind randomized placebo-controlled 2-way crossover study. J Int Soc Sports Nutr. 2016 Feb 19;13:6.
12. Glenn, JM. et al. (2016) Acute citrulline-malate supplementation improves maximal strength and anaerobic power in female, masters athletes tennis players. Eur J Sport Sci. 2016 Nov;16(8):1095-103.
13. Sureda A, et al. L-citrulline-malate influence over branched chain amino acid utilization during exercise. Eur J Appl Physiol. 2010 Sep;110(2):341-51.
14. Ochiai M, et al. Short-term effects of L-citrulline supplementation on arterial stiffness in middle-aged men. Int J Cardiol. 2012 Mar 8;155(2):257-61.
15. Pérez-Guisado J, et al. Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. J Strength Cond Res. 2010 May;24(5):1215-22.
16. Kiyici F, et al. The Effect of Citrulline/Malate on Blood Lactate Levels in Intensive Exercise. Biochem Genet. 2017 Dec;55(5-6):387-394.
17. Chappell AJ, et al. Citrulline malate supplementation does not improve German Volume Training performance or reduce muscle soreness in moderately trained males and females. J Int Soc Sports Nutr. 2018 Aug 10;15(1):42.
18. da Silva DK, et al. Citrulline Malate Does Not Improve Muscle Recovery after Resistance Exercise in Untrained Young Adult Men. Nutrients. 2017 Oct 18;9(10).