Looking over supplement product labels, you’ve likely encountered citrulline malate. Nitric oxide boosters, pre-workout supplements, and male enhancement products all commonly include citrulline malate.
Why is citrulline malate so popular, and what does scientific research tell us about this ingredient? In essence, what are the side effects, either positive or negative, of taking citrulline malate? I dug through the research to find the answers.
Negative Side Effects of Citrulline Malate
Research and anecdotal reports show citrulline malate isn’t strongly associated with any side effects.
This is because citrulline malate is a combination of the amino acid citrulline and the natural chemical malic acid, both of which are safe to use regularly.
A few participants in one study reported slight stomach discomfort after taking citrulline malate. Even so, less than 15% of the participants reported this side effect. And, in other citrulline malate studies, no side effects were reported.
At least for now, it seems citrulline malate is one ingredient you can take without expecting major negative side effects. That quality certainly sets citrulline malate apart from many other ingredients, so it’s no wonder citrulline malate is the go-to supplement for athletes and bodybuilders.
Positive Side Effects of Citrulline Malate
Citrulline malate’s lack of negative effects is just one reason why it’s so popular to use. But, its positive effects are attracting all the attention.
While citrulline gets most of the credit for citrulline malate’s positive effects, both citrulline and malic acid provide exercise and other health benefits.
Let’s start by examining citrulline. Supplements include the amino acid citrulline because it encourages nitric oxide production.
Increasing nitric oxide levels by taking citrulline isn’t a one-step process, however. Citrulline first converts into arginine, another amino acid which directly increases nitric oxide levels.
So, why not take arginine instead? Unfortunately, arginine has limited absorption in the digestive system. In contrast, citrulline absorbs easily, giving it an advantage over arginine. Research confirms taking citrulline increases arginine and nitric oxide levels better than taking arginine.
This positive citrulline side effect explains why it’s found in so many supplement types. Nitric oxide promotes healthy blood flow, which has several effects. In athletes, it means nutrients and oxygen reach cells faster. And, for men trying to combat sexual performance issues, better blood flow means harder erections. Fifty percent of men with mild erectile dysfunction experienced significantly harder erections after taking citrulline for a month.
What does malate bring to the nitric oxide party started by citrulline?
According to a 2002 study from the British Journal of Sports Medicine, the malate in citrulline malate increases cells’ ability to go through the citric acid cycle. The citric acid cycle transforms stored glycogen into more usable energy in the form of ATP. The 6 gram citrulline malate dosage used in this study increased ATP production by 34%. It comes as no surprise then: participants in this study felt significantly less fatigued after taking citrulline malate.
Another study shows even more dramatic fatigue-reduction effects of citrulline malate supplementation. In this study, men who took citrulline malate performed 52.9% more reps of barbell bench presses than those who took the placebo. And, in the next 2 days, their muscles were 40% less sore, meaning citrulline malate decreased muscle recovery time.
Because it simultaneously boosts nitric oxide and ATP production without causing side effects, citrulline malate earns its position as a popular health supplement ingredient.
-  Rodrigues, Joey. “More on Citrulline Malate.” BodyBuilding.com. 2004 Jun 10.
- Perez-Guisada, J, and PM Jakeman. “Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness.” Journal of Strength and Conditioning Research. 24.5 (2010): 1215-22.
-  Moinard, C, I Nicolis, et al. “Dose-ranging effects of citrulline administration on plasma amino acids and hormonal patterns in healthy subjects: the Citrudose pharmacokinetic study.” British Journal of Nutrition. 99.4 (2008): 855-62.
-  Schwedhelm, E, R Maas, et al. “Pharmacokinetic and pharmacodynamics properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism.” British Journal of Clinical Pharmacology. 65.1 (2008): 51-9.
-  Bezaitis, Athan. “How Nitric Oxide Maintains Health.” USC News. University of Southern California. 2009 Feb 18.
-  Cormio, L, M De Siati, et al. “Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction.” Urology.. 77.1 (2011): 119-22.
-  Bendahan, D, JP Mattei, et al. “Citrulline/malate promotes aerobic energy production in human exercising muscle.” British Journal of Sports Medicine. 36.4 (2002): 282-9.