L-arginine vs L-citrulline

Arginine and citrulline are very common compounds that are responsible for the muscle pump effect. Which one to choose? In our article, we compare both preparations to make your choice easier and to present them in a more detailed way.


  1. What is arginine?

L-arginine is one of the endogenous amino acids. Despite this, the human body’s ability to produce it begins to be reduced with age. In addition, it is a very common product – the main source of this compound are products with a significant amount of protein. The most frequently mentioned foodstuffs are milk products (milk, yoghurts), curd cheese, meat (poultry, beef, pork, fish) and some plant foods (soy, almonds, lentils).


  1. The action of arginine

Arginine is considered one of the basic elements of supplementation in strength sports. The above compound is a fundamental substrate in the synthesis of nitric oxide (NO). He is responsible for the expansion of the lumen of the blood vessels in muscle tissue, which enables the delivery of more numerous nutrients. Nitric oxide also affects relaxation of the smooth muscle, which is part of the prevention of heart attacks and promotes the normalization of blood pressure.

Arginine is also a precursor of polyamines. These compounds are very important in protein anabolism. They are primarily responsible for the reproduction of genetic information that is necessary for the synthesis of new proteins in muscle tissues. We are talking not only about specific fragments, but the entire original. This situation occurs when the body needs to create a new cell. It can therefore be concluded that L-arginine is a substance that is not only conducive to the synthesis of protein molecules, but whole muscle cells.

Arginine is also converted in the body by decarboxylase in a compound called agmatine. It is primarily responsible for increasing the level of cyclic nucleotides. In turn, they are involved in the creation of a force impulse of muscle fibers. If you want to learn more about agmatine itself, I refer to the previous text that we published in our portal.

In addition, L-arginine is assigned a number of other health-promoting properties. It is responsible, among others, for wound healing, regulation of the influence of growth hormone and insulin, and also has a strong antioxidant effect. Thanks to this, it promotes purification of the body with ammonia, protection of the nervous system and liver, and also delays the aging process.


  1. Arginine – dosage

The use of arginine should involve the use of specific doses. It is assumed that the daily portion of this substance should be between 3 and 8 g. It is also worth mentioning that the best effects of using arginine occur at the time of its supplementation before training and also before bedtime. This relationship is not free of drawbacks, although the side effects are mainly due to improper supplementation. The most common symptoms include an excessive rise in blood pressure, a drop in the quality of myocardial function and problems with digestion.


  1. Arginine – reviews

When reviewing the literature, it turns out that L-arginine has been the subject of many scientific studies for over 30 years. One example is the 2001 experiment, in which the effect of this compound on the improvement of peripheral and hepatic insulin sensitivity was sought.


The study lasted a quarter and was carried out on a group of 12 people suffering from type II diabetes. A control group of ten healthy people used a normal diet and a placebo. In turn, the research group used the diet for the first two months and took the placebo agent, which was then changed to a portion of 3 g of L-arginine. The results confirmed the effectiveness of using this substance in the treatment of type II diabetes – in the study group there was a decrease in systolic blood pressure (by 14%) and glucose production (by 29%).

Another example is the experience from 2005, which was attended by 80 patients with intermittent claudication. The patients were divided into four groups, where one took placebo and the other

L-arginine (in doses of 3, 6 and 9 g). As the results show, people using a 6-gram portion improved their score (in the passage of the longest and at the same time painless distance) from 113 to 179 meters.


The experiment from 2011 is equally interesting. The researchers carried out an experiment consisting in determining the benefits flowing from oral supplementation with an arginine bolus at a dose of 10 g. The second group of respondents additionally used a 10 g portion of various amino acids. The results confirmed an increase in the level of growth hormone in the blood plasma in people using arginine supplementation after physical exercise.


  1. What is citrulline?

The above name is defined as a chemical compound which is a product of the transformation of another substance called ornithine. This substance is a very important amino acid, although it does not participate in the process of protein synthesis. In our body, it occurs primarily in the urea cycle. Citrulline was obtained from watermelon for the first time. Its natural source are watermelons.


  1. The effect of citrulline

L-citrulline, along with previously described substances – arginine and ornithine – participate in the process of the urea cycle. This cycle is extremely important for the human body, because it leads to the neutralization and detoxification of harmful ammonia. This compound is a side product of amino acid transformation. What’s more, this activity leads to an increase in the pH value in our system, thanks to which it reduces the amount of lactic acid. As is widely known, this substance contributes to the formation of DOMS, which is commonly referred to as “sourdoughs”.


In addition, citrulline is a substrate in the synthesis of nitric oxide (NO). This relationship was often mentioned by me in the context of a muscle pump. What’s more, the company with adenosine triphosphate (ATP) affects the contraction of muscle fibers. Citrulline also regulates blood flow to tissues and accelerates the healing process. This conditions the functioning of human metabolism and also reduces the amount of time needed for regeneration.


  1. Citrulline – dosage

Supplementation with citrulline malate should be in a dose of 2 to 6 g per day. It is recommended that this dose be divided into two smaller portions. First morning (3 g), and the second in the evening or immediately before training. The amount of citrulline used can be increased if our body reacts positively to it. Later it can be successfully taken in an amount of 10 g. It is also worth mentioning that this amino acid is a safe compound and does not cause side effects.


  1. Citrulline – reviews

It turns out that there is a large number of empirical evidence for the health-promoting effects of L-citrulline. The first example can be tests carried out at the Pudure University. Although the mice were the research material, the results confirm that the systematic use of watermelon juice (and hence the citrulline included in it) reduces the accretion rate by more than 50% of LDL cholesterol.


Another research is the experiment of scientists from the Technical University of Carthage. Researchers administered three preparations of watermelon juice, juice with an additional portion of citrulline malate and a control substance to volunteers one hour before the workout. As it turned out, the first two beverages significantly influenced the reduction of pain symptoms from the muscular system. In addition, the first specific showed greater bioavailability. The above test also had one more goal – to demonstrate the effect of citrulline on cancer cells of colon cancer.

Scientists used this time a pasteurized and unpasteurized watermelon drink and water. Each of the preparations had identical content

L-citrulline. After almost 10 minutes, it turned out that the test compound was absorbed from unpasteurized juice. It can therefore be assumed that despite the reduction of harmful microbes by the pasteurization process, it leads to a reduction of bioavailability.


  1. L-arginine vs L-citrulline – verdict

It is difficult to state clearly which of the preparations is better. On the one hand, arginine in addition to the synthesis of nitric oxide contributes to the formation of new protein structures and agmatine. What’s more, its use carries a number of pro-health benefits for the body. On the other side we have citrulline, which is more conducive to regeneration and removal of urea from the body. In addition, the product is completely safe to use, and therefore its doses may be increased over time.

In conclusion – you have to decide for yourself which of the preparations is more appealing to you and will be better suited to your expectations. It’s worth to confront each of these supplements with your own training plan and other nutrients (if you use any). Personally, I would suggest each of them to test on themselves and see which will work better for you. Despite many similarities in physiology, each organism is different and what works for one person does not have to be beneficial to the other.