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L-Citrulline
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Table of contents
- Definition: What is L-Citrulline?
- What are the functions of L-citrulline?
- L-Citrulline: Effects on men
- Do L-arginine and L-citrulline increase testosterone levels?
- What effect does L-citrulline have on the psyche?
- What makes L-citrulline unique?
- Is L-arginine or L-citrulline better?
- How much L-citrulline do you need per day?
- When do you especially need L-citrulline?
- Citrulline supplements for athletes
- How does a deficiency of L-citrulline develop and what are its symptoms?
- What should you pay attention to when taking L-citrulline?
- What is L-citrulline malate powder?
- Which foods contain particularly high levels of L-citrulline?
- Bibliography & Sources
Definition: What is L-Citrulline?
Citrulline is a basic, non-proteinogenic amino acid. Unlike proteinogenic amino acids, non-proteinogenic amino acids are not components of proteins.
Only the L-form of citrulline has biological significance. The mirror-image D-citrulline plays no role for humans. Therefore, high-quality dietary supplements contain only L-citrulline.
Citrulline owes its name to the watermelon, or Citrullus lanatus in Latin. Watermelons are particularly rich in this nutrient.¹
What are the functions of L-Citrulline?
L-citrulline is the direct precursor to the semi-essential amino acid arginine.² This, in turn, is a central building block for the body's own production of nitric oxide (NO). Nitric oxide is an important messenger substance that has a vasodilating effect and is therefore important for blood circulation and the health of the cardiovascular system.
L-citrulline, which is first converted into L-arginine and finally into nitric oxide, helps to lower blood pressure.³ Your muscles are better supplied with blood, which means more nutrients and oxygen reach the tissue, increasing performance. The veins become visibly prominent, which is known as the "pump effect" among bodybuilders.⁴
L-Citrulline: Effects on men
The vasodilation caused by nitric oxide, which is produced with the help of L-citrulline or L-arginine, plays an essential role in male potency. Good blood flow to the erectile tissue is important to achieve and maintain an erection. It is the inflowing blood that provides the necessary firmness of the penis.
Do L-arginine and L-citrulline increase testosterone levels?
Neither L-arginine nor L-citrulline have testosterone-boosting effects. However, both substances lead to an increased release of nitric oxide (NO) and thus to better blood circulation. This can improve a man's erectile function – but this is a vascular effect, not a hormonal one.
In addition, L-arginine and L-citrulline can help to increase training volume⁵ and reduce fatigue after exercise. Since intense strength training can temporarily raise testosterone levels⁶, the effect of the two amino acids should rather be considered indirect.
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What effect does L-citrulline have on the psyche?
L-citrulline does not have a direct mood-enhancing effect. However, through its role in nitric oxide metabolism and the associated improved blood flow, this amino acid can help reduce feelings of fatigue, particularly in the context of physical exertion and after long training sessions.⁷
What makes L-Citrulline unique?
L-citrulline has a higher bioavailability than L-arginine. This means that it can be more easily absorbed by the body. There is scientific evidence that orally administered L-citrulline is more efficient than L-arginine itself.⁸ More than 80 percent of the citrulline reaches the kidneys. There, L-citrulline is converted into L-arginine, which allows it to unfold its full effect.⁹
Is L-arginine or L-citrulline better?
High-quality dietary supplements often combine these two amino acids. While L-arginine acts more quickly, L-citrulline must first be converted into L-arginine in the body. However, L-citrulline can help inhibit the breakdown of arginine by the enzyme arginase, thus making more arginine available to the body overall.¹⁰
How much L-citrulline do you need per day?
Your body can produce L-citrulline itself. It is therefore a non-essential amino acid, meaning that this substance does not necessarily have to be ingested through food. Therefore, the German Nutrition Society (DGE) provides no recommendations for daily L-citrulline requirements.
The body's own production of L-citrulline occurs via the intestinal wall. This substance is formed as an intermediate product of the urea cycle from ornithine and carbamoyl phosphate and further reacts with aspartate to form argininosuccinate. The latter is finally converted into the proteinogenic amino acid arginine.¹¹
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When do you especially need L-citrulline?
There is scientific evidence that L-citrulline may have a potentially positive effect on vascular health and early vascular changes. Initial studies suggest that L-citrulline supplementation increases arginine levels, thereby lowering blood pressure and the risk of atherosclerosis.¹² If you belong to a risk group for these health problems, you should talk to your doctor about whether taking L-citrulline is right for you.
Citrulline supplements for athletes
Furthermore, L-citrulline can improve muscle blood flow, which makes this supplement interesting for athletes. On the one hand, it increases energy metabolism and cellular respiration in the muscles, and on the other hand, it enhances muscle growth and supports recovery after training.¹³
If a circulatory disorder is the cause of existing erectile dysfunction, citrulline can also have a supportive effect.1⁴
How does a deficiency of L-citrulline develop and what are its symptoms?
Since L-citrulline is produced by the body itself, a deficiency is unlikely. It probably arises as a result of intestinal damage, such as from short bowel syndrome, a previous intestinal transplant, or other chronic intestinal diseases. Certain cardiovascular diseases and diabetes mellitus can lead to disturbances in nitric oxide metabolism, thereby increasing the need for citrulline.
Possible consequences of a deficiency include impaired wound healing and a weakened immune system. Due to the inadequate blood flow, the risk of vascular diseases such as arteriosclerosis is increased.
What should you pay attention to when taking L-citrulline?
According to the Federal Office of Consumer Protection and Food Safety, dietary supplements containing L-arginine and L-citrulline are not suitable for children, pregnant women, breastfeeding mothers, or people who have suffered a heart attack. If you are taking medication to lower blood pressure, are on a low-protein diet, or suffer from kidney or liver disease, you should consult your doctor before taking L-citrulline in tablet, capsule, or powder form.¹⁵
What is L-citrulline malate powder?
The recommended daily dose is 3,000 milligrams of L-citrulline. Athletes, as well as people with high blood pressure, erectile dysfunction, or arteriosclerosis, can increase the dose if needed and after consulting their doctor. Citrulline is available pure, in combination with arginine, or as L-citrulline malate. Citrulline malate powder combines the esters and salts of malic acid with citrulline.
Which foods contain particularly high levels of L-citrulline?
Since the non-proteinogenic amino acid L-citrulline is not a building block of proteins, it is not necessarily found in high concentrations in protein-rich foods, unlike many other amino acids. The food richest in citrulline is watermelon – this amino acid owes its name to it.
Other good sources include other members of the cucurbit family such as cucumber, zucchini, and cantaloupe. However, oral intake plays a rather minor role compared to other nutrients, as the body can produce L-citrulline itself.
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This encyclopedia entry is based on carefully researched sources:
Bibliography & Sources
- chemie.de/lexikon/Citrullin.html
- vitamindoctor.com/naehrstoffe/aminosaeuren/citrullin
- pubmed.ncbi.nlm.nih.gov/30788274/
- ndr.de/ratgeber/gesundheit/arginin-wirkung-des-supplements-l-arginin,arginin-102.html
- pubmed.ncbi.nlm.nih.gov/30847640/
- pubmed.ncbi.nlm.nih.gov/15831061/
- pubmed.ncbi.nlm.nih.gov/26900386/
- pubmed.ncbi.nlm.nih.gov/17662090/
- vitamindoctor.com/naehrstoffe/aminosaeuren/citrullin
- ndr.de/ratgeber/gesundheit/arginin-wirkung-des-supplements-l-arginin,arginin-102.html
- chemie.de/lexikon/Citrullin.html
- pubmed.ncbi.nlm.nih.gov/41058823/
- pubmed.ncbi.nlm.nih.gov/26900386/
- pubmed.ncbi.nlm.nih.gov/21195829/
- bvl.bund.de/DE/Arbeitsbereiche/01_Lebensmittel/04_AntragstellerUnternehmen/07_Allgemeinverfuegungen/01_Archiv_Uebersicht/07_Nahrungsergaenzungsmittel/lm_av2350_018_01_basepage.html
