The amino acid citrulline is gaining popularity as a supplement for health and exercise performance.
It’s produced naturally in the body and found in foods, but taking supplements increases citrulline content in the body above typical levels.
While some people are convinced of its effectiveness for health and exercise performance, others are skeptical.
This article will tell you everything you need to know about citrulline and whether you should take it.
It is considered nonessential, meaning that your body can naturally produce some on its own.
However, you can increase your levels by eating foods containing citrulline or by taking dietary supplements, rather than relying on your body’s production alone.
These higher levels may produce beneficial effects on health and exercise performance, as discussed later in this article.
Citrulline has important roles in the body, but unlike some amino acids, it is not used to build proteins.
However, it plays a necessary part in the urea cycle, which rids your body of harmful compounds. Specifically, the urea cycle removes ammonia from the body. The final product of this cycle is urea, which your body gets rid of in urine.
Citrulline can also help widen your blood vessels and may play a role in muscle building.
One major way it works is by increasing vasodilation.
Vasodilation refers to the widening of arteries or veins. It’s associated with lower blood pressure and increased blood flow (5Trusted Source).
After citrulline is consumed, some is converted to another amino acid called arginine.
Arginine is converted into a molecule called nitric oxide, which causes vasodilation of blood vessels by relaxing the smooth muscle cells that constrict them (6Trusted Source).
Interestingly, consuming citrulline may increase arginine in the body more than consuming arginine itself (4Trusted Source).
This is because of differences in how the body processes and absorbs arginine and citrulline (2Trusted Source).
The increase in nitric oxide and blood flow may be one of the processes involved in citrulline’s beneficial effects on exercise performance.
Although citrulline isn’t an amino acid used directly to build proteins, it has been shown to increase protein synthesis by stimulating an important signaling pathway involved in muscle building (2Trusted Source, 7Trusted Source).
Citrulline may also reduce the liver’s uptake of certain amino acids and prevent their breakdown (4Trusted Source).
Through these dual effects on protein synthesis and amino acid breakdown, it may contribute to maintaining or increasing muscle mass.
However, most foods have not been analyzed for their content of this amino acid.
Foods known to contain citrulline include (7Trusted Source, 8Trusted Source):
However, when citrulline malate is used, it isn’t clear which health effects are due to citrulline and which are due to malate.
Studies have shown that a single dose of L-citrulline does not improve the ability of the arteries to widen in either healthy or diseased individuals (11Trusted Source, 12Trusted Source).
However, when people who have heart disease or are at risk of heart disease have consumed L-citrulline for seven days or longer, the ability of their arteries to widen has improved (13Trusted Source, 14Trusted Source).
So, although a single dose may not be very effective at widening your blood vessels, taking supplements in the longer term may be more effective.
Studies of 30 to 40 participants looked at the effects of citrulline supplements in adults with high blood pressure or other heart conditions.
They found that participants’ blood pressure had reduced by 4–15% after eight weeks (15Trusted Source, 16Trusted Source).
What’s more, in a small study examining 12 adults with normal blood pressure, researchers found that citrulline reduced blood pressure by 6–16% after 7 days (17Trusted Source).
However, the evidence in healthy individuals is not conclusive, since other researchers found no benefit of citrulline over periods of one to four weeks (14Trusted Source, 18Trusted Source).
Overall, it is unclear if it substantially affects blood pressure in healthy individuals.
The post-exercise rise in GH and other hormones may be involved in the beneficial adaptations your body experiences when you exercise (20Trusted Source).
The amino acid may also improve erections in men with erectile dysfunction, probably through its ability to increase blood flow (21Trusted Source).
It’s produced naturally in the body and found in foods, but taking supplements increases citrulline content in the body above typical levels.
While some people are convinced of its effectiveness for health and exercise performance, others are skeptical.
This article will tell you everything you need to know about citrulline and whether you should take it.
What Is Citrulline?
Citrulline is an amino acid that was first found in watermelon.It is considered nonessential, meaning that your body can naturally produce some on its own.
However, you can increase your levels by eating foods containing citrulline or by taking dietary supplements, rather than relying on your body’s production alone.
These higher levels may produce beneficial effects on health and exercise performance, as discussed later in this article.
Citrulline has important roles in the body, but unlike some amino acids, it is not used to build proteins.
However, it plays a necessary part in the urea cycle, which rids your body of harmful compounds. Specifically, the urea cycle removes ammonia from the body. The final product of this cycle is urea, which your body gets rid of in urine.
Citrulline can also help widen your blood vessels and may play a role in muscle building.
How Does It Work?
Citrulline produces several important effects in the body.One major way it works is by increasing vasodilation.
Vasodilation refers to the widening of arteries or veins. It’s associated with lower blood pressure and increased blood flow (5Trusted Source).
After citrulline is consumed, some is converted to another amino acid called arginine.
Arginine is converted into a molecule called nitric oxide, which causes vasodilation of blood vessels by relaxing the smooth muscle cells that constrict them (6Trusted Source).
Interestingly, consuming citrulline may increase arginine in the body more than consuming arginine itself (4Trusted Source).
This is because of differences in how the body processes and absorbs arginine and citrulline (2Trusted Source).
The increase in nitric oxide and blood flow may be one of the processes involved in citrulline’s beneficial effects on exercise performance.
Although citrulline isn’t an amino acid used directly to build proteins, it has been shown to increase protein synthesis by stimulating an important signaling pathway involved in muscle building (2Trusted Source, 7Trusted Source).
Citrulline may also reduce the liver’s uptake of certain amino acids and prevent their breakdown (4Trusted Source).
Through these dual effects on protein synthesis and amino acid breakdown, it may contribute to maintaining or increasing muscle mass.
It Is Found in Some Common Foods
In addition to being produced in the body, citrulline is found in several foods.However, most foods have not been analyzed for their content of this amino acid.
Foods known to contain citrulline include (7Trusted Source, 8Trusted Source):
- Watermelon
- Pumpkins
- Cucumber
- Bitter melon
- Gourds
Types of Citrulline Supplements
There are two major forms of citrulline in dietary supplements:- L-citrulline: This simply refers to citrulline by itself, with nothing else attached.
- Citrulline malate: This refers to the combination of citrulline and another compound called malate, which is important for energy production (9Trusted Source).
However, when citrulline malate is used, it isn’t clear which health effects are due to citrulline and which are due to malate.
It Has Several Benefits for Your Health
Researchers have looked into citrulline’s potential health effects, including effects on blood vessels, erectile dysfunction and exercise performance (5Trusted Source, 10Trusted Source).It May Help Your Blood Vessels Widen
Improving the ability of the blood vessels to widen can potentially improve blood pressure and blood flow to tissues.Studies have shown that a single dose of L-citrulline does not improve the ability of the arteries to widen in either healthy or diseased individuals (11Trusted Source, 12Trusted Source).
However, when people who have heart disease or are at risk of heart disease have consumed L-citrulline for seven days or longer, the ability of their arteries to widen has improved (13Trusted Source, 14Trusted Source).
So, although a single dose may not be very effective at widening your blood vessels, taking supplements in the longer term may be more effective.
It May Reduce Blood Pressure
Citrulline supplements may decrease blood pressure, particularly in people with high blood pressure.Studies of 30 to 40 participants looked at the effects of citrulline supplements in adults with high blood pressure or other heart conditions.
They found that participants’ blood pressure had reduced by 4–15% after eight weeks (15Trusted Source, 16Trusted Source).
What’s more, in a small study examining 12 adults with normal blood pressure, researchers found that citrulline reduced blood pressure by 6–16% after 7 days (17Trusted Source).
However, the evidence in healthy individuals is not conclusive, since other researchers found no benefit of citrulline over periods of one to four weeks (14Trusted Source, 18Trusted Source).
Overall, it is unclear if it substantially affects blood pressure in healthy individuals.
Other Health Benefits
Citrulline can increase the rise in growth hormone (GH) seen after exercise (19Trusted Source).The post-exercise rise in GH and other hormones may be involved in the beneficial adaptations your body experiences when you exercise (20Trusted Source).
The amino acid may also improve erections in men with erectile dysfunction, probably through its ability to increase blood flow (21Trusted Source).
