Citrulline is an α-amino acid (alpha-amino acid), that is a non-proteic amino acid that is found in high concentrations in watermelon, from which it receives its name deriving from the Latin term for watermelon (Citrullus vulgaris).

Citrulline is usually available in the form of citrulline malate supplements.

This compound consists of esterified citrulline amino acid together with malic acid (an apple derivative).

The latest clinical research has discovered the enormous potential of citrulline (in the form of citrulline malate) as a dietary supplement, which is perfect for people who do bodybuilding or endurance sports. What is the reason for this? What benefits can be expected of citrulline? We'll explain it to you in detail here.

Citrulline improves performance in bodybuilders and those involved in endurance sports

One of the most important studies on the effects of citrulline in bodybuilders was published in 2010 by Perez-Guisado and Jakeman in the "Strength and Conditioning Journal". This study measured the different levels of physical endurance in the bench press of 41 men, comparing the results between those who had been given citrulline malate and those who took a placebo.

The men being studied executed their moves with the bench press, doing 80% of their maximum repetitions followed by a pause for 60 seconds.

It was observed that starting from the third repetition, those who had taken citrulline malate had a considerably superior performance, doing up to almost 53% more bench press repetitions than those who had taken a placebo.

It was also found that those who had taken citrulline malate experienced a reduction of 40 percent in muscle aches during 24-48 hours after the training session, compared to the placebo group. Those participating in this study had taken 8 grammes of citrulline malate, 1 hour before training.

Citrulline also has positive effects on physical recovery, producing a greater elimination of ammonia (NH3). Ammonium is very dangerous and can kill cells, increase infections caused by viruses and promote the growth of cancer cells. Those involved in the sport of bodybuilding have a high protein intake, which carries the risk of the body accumulating ammonium, so we recommend paying more attention to the elimination of this toxic substance.

Citrulline’s properties also include the fact that it is a precursor to the endogenous synthesis of creatine.

Athletes who do intensive training can achieve better performances by taking citrulline, especially those who predominantly do anaerobic activities like bodybuilding, weight training and resistance-based sports.

This is probably due to the fact that a greater muscle detoxification and elimination of ammonia play important roles in increasing physical performance. In a 2010 clinical study, it was found that taking 6 grammes of citrulline malate increased levels of growth hormones in cyclists to an impressive extent, from 24% to 66% compared to those who took a placebo.

It was also found that after three days of intensive training an increase of growth hormones of around 28% was detected.

Human growth hormone (HGH) acts on anabolic amino acids and lipolytic fat cells (shedding fat). Because of these unique effects, HGH is also used to increase resistance in different sports, such as bodybuilding.

If you acquire these levels of growth hormone through the administration of citrulline malate it can give a clear you athletic advantage. The effects of citrulline malate are magnified when it is eaten on an empty stomach.

This trial also revealed that after taking citrulline malate a more effective result of the amino acids is produced, especially of the branched chain amino acids (BCAA). This improved usage brings about an increase in energy during training.

Comparison of citrulline with arginine

Scientific studies are focusing on the study of citrulline, as the semi-essential amino acid, arginine, is metabolised relatively quickly in the ornithine cycle (urea).

Arginine is an amino acid that is converted to nitric oxide in the blood. Arginine helps to stimulate the production of growth hormones, natural sterols that help rebuild muscles after intensive training.

Citrulline also acts as a vasodilator, helping to open up and expand blood vessels. Citrulline, also helps to remove nitric acid and lactic acid that are generated in the intensive training involved in muscle-building exercises and other resistance-based sports.

Citrulline produces a greater increase of NO (nitric oxide) levels than does arginine. If arginine is taken directly, the amino acid is processed and degraded in the liver by the enzyme arginase. Arginine is first oxidised and then the citrulline through the release of nitric oxide. Citrulline facilitates the production of arginine.

Clinical studies have also shown that citrulline malate increases the levels of plasma in tissues more than arginine. In general, arginine is arguably more effective in the short term, while citrulline is more effective in the long run.

Citrulline also promotes vasodilation (widening of the blood vessels) and increased blood flow. With increase blood flow oxygen and nutrients are better distributed to the muscles, promoting physical performance and a higher capacity for intense training, thereby obtaining better results in muscle development and resistance-based sports.

It is believed that citrulline produces the same effects as arginine, but that it also has other beneficial effects that arginine lacks.

Another advantage of citrulline malate is that it has a better flavour (similar to lemon juice) than arginine. The pleasant taste of citrulline malate is mainly due to the esterification of citrulline with malic acid, which has a lemon flavour. In summary, citrulline is far superior to arginine in many respects.

The role of nitric oxide (NO) in the human body

Nitric oxide is involved in various processes in the human body. It regulates blood flow, vasodilation, platelet function and mitochondrial respiration among other things. As a result nitric oxide can make the blood circulate faster and reach all the parts of the body, thereby increasing the flow of blood and oxygen to the cells. This increase contributes to a better physical performance and recovery after physical effort and training.

Conclusion, recommended doses of citrulline malate

In summary, we can say that citrulline is an amino acid with great future potential, since many of its benefits may still be waiting to be discovered by science. Although the effects on strength have been proven in clinical studies, we have pointed out that they do not occur in everyone to the same degree. Citrulline malate presents other less obvious effects, such as elevated levels of HGH, which can offer clear advantages to athletes, especially with regard to the reduction of lactic acid and ammonia, therefore being of great assistance to bodybuilders.

The recommended dosage of citrulline malate ranges from 5 to 8 grammes.

The only observed side effect consists of a mild abdominal pain, though it only manifests itself in 10 to 15 percent of the observed subjects, who had ingested 8 grammes of citrulline malate.

However, people suffering from cardiovascular illnesses or who are taking blood thinners should be careful and first consult a physcian before taking citrulline malate. Although science currently considers citrulline as a potential "medicine", more trials must be undertaken to assess its effects.

In short: citrulline, as with any other dietary supplement, is not a panacea, but for those who are looking for a supplement that provides improved heart function, increased blood flow and higher HGH levels, citrulline malate is the best option.


  • Perez Guisado J, Jak Eman PM.: Citrulline malate, improvements in anaerobic athletic performance and muscle pain.
  • A Sureda, A. Pons: Arginine supplements and citrulline in sports and exercise: ergogenic nutrients?
  • Sureda A Cordova A, Ferrer MD, Perez G, TUR, Pons, A.: Influence of L - citrulline malate on the utilisation of branched chain amino acids during exercise.
  • Willard J. Visek: Diet and modulation growth through ammonium
  • Caldwell, Caldwell RB, Romero MJ, DH Platt RW.: Therapeutic use of citrulline in cardiovascular disease.
  • Bescos R, Sureda A, Pons A.: The effect of nitric oxide supplements in physical performance.