Citrulline is an amino acid with a wide range of health benefits.
Taking citrulline supplements can reduce blood pressure and improve the ability of your arteries to expand.
The body can produce it naturally, and it is also available in some foods.
However, taking supplements increases the body’s citrulline content above typical levels.
While some people are aware of citrulline benefits for health and performance in exercise, others are skeptical.
How Does It Work?
Citrulline has several essential effects on the body. It operates primarily by enhancing vasodilation. The expansion of arteries or veins is referred to as vasodilation.
It has been linked to decreased blood pressure and enhanced blood flow (1).
After consuming citrulline, some of it is transformed into another amino acid known as arginine.
Arginine is turned into the chemical nitric oxide, which induces blood vessel dilatation by relaxing the smooth muscle cells that constrict them (2).
Ingesting citrulline may enhance arginine levels in the body more than arginine alone (3).
This is because of changes in how the body processes and absorbs arginine and citrulline (4).
One process involved in citrulline’s favorable benefits of exercise performance may be an increase in nitric oxide and blood flow.
Although citrulline is not an amino acid that is directly used to make proteins, it has been shown to boost protein synthesis by triggering a key signaling pathway involved in muscle development (5).
Citrulline may also decrease the intake of some amino acids by the liver and prevent their degradation (3).
It may help to maintain or increase muscle mass by having dual effects on protein synthesis and amino acid degradation.
Reduces Blood Pressure
Citrulline supplements can help lower blood pressure, especially in people who have high blood pressure. Studies in 40 participants show the effects of citrulline supplements on adults with high blood pressure or other heart conditions (6, 7).
They found that after eight weeks, the blood pressure of participants had decreased by 4–15%.
In a small study, researchers found that citrulline reduced blood pressure by 6–16% after 7 days, examining 12 adults with normal blood pressure (8).
The evidence is not conclusive in healthy individuals, as other researchers found no benefits from citrulline over periods of four weeks (9).
Overall, it is unclear whether it significantly affects healthy individuals’ blood pressure.
Widens Blood Vessels
Improving the ability of blood vessels to expand may enhance blood pressure and flow.
Studies have shown that a single dose of L-citrulline does not enlarge arteries in healthy or ill individuals (10, 11).
However, people who have heart disease or are at risk of heart disease have consumed L-citrulline for seven days or more had improved the ability of their arteries to widen (12), (13).
So, while a single dose may not be very effective in widening your blood vessels. Thus, taking citrulline supplements may have benefits over the long term.
Boosts Exercise Performance
Citrulline was studied in both endurance and strength-based exercises due to its ability to improve blood flow.
Several endurance exercise studies have used L-citrulline, while much of the resistance-based research has used citrulline malate.
A single dose of citrulline does not appear to improve the performance of endurance exercises (14).
Taking citrulline supplements for one to two weeks does not affect oxygen consumption. It can increase oxygen in muscle tissue (15).
This means the amino acid may not allow the body to use more oxygen. However, it may improve oxygen utilization in the exercising muscle.
This may allow for better results in exercise. Cyclists taking citrulline could cycle 12% longer before exhaustion than those taking placebos in one study (16).
Taking these supplements can also improve power output during cycling. In a certain amount of time, that is how much force it can produce.
Citrulline can affect the oxygen in the muscles, which can improve stamina (14).
Boosts Growth Hormone (GH)
Citrulline may boost growth hormone (GH) after exercise, which can cause muscle growth (17).
It may involve the rise in GH and other hormones after exercise in the beneficial adaptations that your body experiences when you are exercising (18).
The amino acid may also improve erections in men with erectile dysfunction, possibly by increasing blood flow (19).
Builds Muscle Faster
Several studies have shown that citrulline malate has the benefit of enhancing performance in weight training.
One study in 41 men examined the ability to perform repetitions during upper-body exercise (20).
After the consumption of citrulline malate, participants could perform 53% more repetitions than the placebo.
When they consumed citrulline malate before exercising, the participants’ muscle soreness after exercise was 40% less.
Other researchers also found that citrulline malate can reduce tiredness and increase the performance of the lower body in weight training (21).
Participants had taken the supplement 60 minutes before exercise in both studies.
Types of Citrulline
In dietary supplements, there are two primary forms of citrulline:
This refers to citrulline by itself, with nothing else combined.
Citrulline Malate: This refers to the combination of citrulline and another compound called malate, which is important for the production of energy (22).
Safety and Side Effects
However, the highest doses of arginine in the blood did not appear to increase as much as expected, meaning there is a limit to how much of this supplement your body can use.
Overall, the study showed that excessive doses are greater than 10 grams. Blood tests conducted in participants after taking citrulline supplements revealed no harmful changes to normal body functions or blood pressure. (23).
Conclusion
Citrulline is an amino acid that has several health benefits. It also seems to be safe, with no known side effects.
This supplement can promote healthy blood vessels and lower blood pressure, especially in people with heart disease or high blood pressure.
Citrulline malate was researched the most for weight training. An 8-gram dose could reduce fatigue and boost workout performance.
Citrulline may be the next supplement you should consider if you want to support heart health or boost your workout performance.
We strongly recommend consulting with your doctor before taking any supplements.
