Citrulline is a naturally occurring amino acid in your body and can also be sourced from various foods or through dietary supplements. Boosting your intake with citrulline supplements might enhance your health and athletic capabilities.
Recently, the spotlight has been on citrulline as a potential powerhouse for both health benefits and athletic prowess.
Although our bodies naturally produce this amino acid and it’s present in many foods, supplementing can elevate citrulline levels beyond the usual.
Opinions vary: while many advocate its positive impacts on health and athletic performance, some remain doubtful.
Delve into this guide to uncover the facts about citrulline and determine if it’s the right supplement for you.
In this article
What is citrulline?
Citrulline is an amino acid originally discovered in watermelon.
While it’s labeled as nonessential – implying our bodies can produce it on their own – there’s a benefit to boosting its levels through food or dietary supplements instead of just depending on natural production.
Elevated levels of citrulline can enhance both health and athletic performance, as we’ll explore further.
Interestingly, while citrulline plays vital roles within our system, it doesn’t contribute to protein synthesis like some other amino acids. Its primary function? Participating in the urea cycle. This essential process detoxifies our body by eliminating ammonia. The end product, urea, is then expelled from our system through urine.
Moreover, citrulline has the potential to expand blood vessels and might contribute to muscle growth.
Summary: Citrulline is an amino acid that naturally occurs in the body, and is also found in food and available as a dietary supplement. Increasing your intake may have positive effects on your health and exercise performance.
How does citrulline work?
Citrulline plays pivotal roles in our body’s health.
A primary function is its ability to promote vasodilation.
Vasodilation is the process of enlarging blood vessels. This phenomenon helps decrease blood pressure while enhancing blood circulation.
When you ingest citrulline, it transforms into another vital amino acid named arginine.
This arginine then morphs into nitric oxide. Nitric oxide induces vasodilation by making the muscle cells lining the blood vessels relax.
Remarkably, taking citrulline can elevate arginine levels in the system more than ingesting arginine directly.
This unique property stems from the distinct ways our body digests and absorbs the two amino acids.
Nitric oxide’s augmentation and improved blood circulation are potentially key to understanding citrulline’s positive impact on physical activity.
Even though citrulline isn’t a direct participant in protein formulation, research suggests it enhances protein creation by activating a crucial muscle-building signaling pathway.
Additionally, citrulline can limit the liver from absorbing certain amino acids, thereby preventing their degradation.
These combined roles in protein creation and amino acid preservation may be essential for sustaining or augmenting muscle bulk.
Summary: Citrulline may increase blood flow by increasing nitric oxide production. It may also positively affect muscle by stimulating protein synthesis and decreasing amino acid breakdown.
Citrulline is found in some common foods
In addition to being produced in the body, citrulline is found in several foods.
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However, most foods have not been analyzed for their amino acid content.
Foods known to contain citrulline include:
- Watermelon
- Pumpkins
- Cucumber
- Bitter melon
- Gourds
Summary: Citrulline is found in several foods, especially watermelon. Most foods have not been explicitly analyzed for their citrulline content.
Types of citrulline supplements
There are two significant forms of citrulline in dietary supplements:
- L-citrulline: This 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 essential for energy production.
While the two forms may produce some similar effects, citrulline malate is more common in sports supplements.
However, when citrulline malate is used, it isn’t clear which health effects are due to citrulline and which are due to malate.
Summary: L-citrulline and citrulline malate are the two forms typically found in dietary supplements. Citrulline and malate can each exert effects on the body.
Health benefits of citrulline
Researchers have looked into citrulline’s potential health effects, including effects on blood vessels, erectile dysfunction, and exercise performance.
Citrulline 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 arteries’ ability to widen in healthy or diseased individuals.
However, when people with 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.
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.
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Citrulline 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.
In a small study examining 12 adults with normal blood pressure, researchers found that citrulline reduced blood pressure by 6–16% after 7 days.
However, the evidence in healthy individuals is inconclusive, since other researchers found no benefit of citrulline over one to four weeks.
Overall, it is unclear if it substantially affects blood pressure in healthy individuals.
Other health benefits of citrulline
Citrulline can increase the rise in growth hormone (GH) seen after exercise.
The post-exercise rise in GH and other hormones may be involved in the beneficial adaptations your body experiences when you exercise.
The amino acid may also improve erections in men with erectile dysfunction, probably through its ability to increase blood flow.
Summary: Taking citrulline supplements may reduce blood pressure and improve your arteries’ widening ability. These effects may occur more consistently in people with disease.
Citrulline for exercise performance
Due to its ability to increase blood flow, citrulline has been studied in the context of both endurance and strength-based exercise.
Several endurance exercise studies have used L-citrulline, while much of the strength-based research has used the form of citrulline malate.
Endurance exercise
A single dose of citrulline does not seem to improve endurance exercise performance.
Taking supplements for one to two weeks does not change oxygen consumption.
However, it can increase the oxygen content in muscle tissue.
This means that although the amino acid may not allow more oxygen to be used by the body as a whole, it could improve oxygen usage in the exercising muscle. This may ultimately allow for better exercise performance.
This has been demonstrated in cycling, where citrulline supplements can increase performance.
In one study, cyclists taking citrulline could cycle for 12% longer before exhaustion than those taking a placebo.
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Taking these supplements for seven days can also improve power output during cycling. That’s how much force can be produced in a certain amount of time.
Overall, this supplement may beneficially affect oxygen usage in muscles, which could improve endurance.
Weight training
Several studies have shown that citrulline malate can improve weight training performance.
One study in 41 men assessed the effects of citrulline malate on the ability to perform repetitions during upper body exercise.
Participants were able to perform 53% more repetitions after ingesting citrulline malate, compared to a placebo.
Moreover, participants’ muscle soreness in the two days after exercise was 40% lower when they consumed citrulline malate before exercising.
Other researchers also found that citrulline malate decreased fatigue and increased lower body weight training performance.
In both of these studies, participants took the supplement 60 minutes before exercise.
Summary: Citrulline may increase oxygen content in the muscles and improve exercise performance. Both endurance performance and weight training performance may be improved by taking supplements.
How much citrulline should you take?
Based on current research, a recommended dose is 3–6 grams per day of L-citrulline or approximately 8 grams per day of citrulline malate.
The dose varies depending on the form because 1.75 grams of citrulline malate provides 1 gram of L-citrulline. The remaining 0.75 grams are malate.
Below are recommendations for specific uses:
- Weight training: Eight grams of citrulline malate provide about 4.5 grams of citrulline, an effective dose for weight training performance.
- Oxygen in muscle: To improve oxygen content in muscle, taking 6 or more grams of L-citrulline daily for seven days seems effective.
- Blood pressure: For improving blood pressure, the daily dose of L-citrulline used in research is typically 3–6 grams daily.
Furthermore, doses of 10 or more grams do not typically cause an upset stomach, unlike other amino acids.
An upset stomach is a sure way to derail a workout, so this is good news if you are taking this supplement to boost exercise performance.
Citrulline is probably better tolerated due to differences in how it is absorbed and processed compared to other amino acids.
Summary: Doses of 3–6 grams of L-citrulline or 8 grams of citrulline malate may be optimal. No known side effects have been reported with doses of at least 10 grams.
Safety of citrulline supplements
While there is limited research on the safety of taking citrulline supplements at higher doses, some preliminary information is available.
One small study examined different doses in eight healthy men. Each participant consumed doses of 2, 5, 10, and 15 grams of L-citrulline at separate visits.
Even with the highest doses, the participants reported no side effects.
However, the highest doses did not appear to increase arginine in the blood as much as expected, meaning there is a limit to how much of this supplement your body can use. Overall, the study indicated that doses greater than 10 grams are unnecessary.
Blood analysis performed on participants after taking citrulline supplements showed no adverse changes to normal body functions or blood pressure.
Summary: Based on current information, citrulline is safe and well-tolerated. However, doses of greater than 10 grams are probably unnecessary.
Summary
Citrulline is a beneficial amino acid that boasts numerous health advantages. It’s recognized for its safety, with no reported adverse effects to date.
This nutrient can support robust blood vessels and potentially reduce blood pressure, particularly in individuals with cardiac issues or elevated blood pressure.
In the realm of weight training, citrulline malate garners the most attention. An intake of 8 grams might diminish tiredness and enhance workout results.
Seeking a boost for your cardiac health or aiming to elevate your fitness regime? Citrulline could be the supplement to add to your list.
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