Citrulline: Amino Acid that Benefits Blood Flow & Performance (+ Foods & Dosage Info)

Citrulline is an amino acid often used to improve overall health and ramp up your fitness routine. Although it’s not considered an essential amino acid, it is still incredibly important to health, and there is a wide array of L-citrulline benefits.

Getting in your fix of foods rich in this key compound can help support better blood flow, enhance oxygen uptake and promote muscle growth, among other potential L-citrulline benefits.

So what is L-citrulline, and how can it impact your health? Keep reading for everything you need to know about this important amino acid, including the top L-citrulline benefits, plus some simple ways to quickly boost your intake.

What is citrulline?

Citrulline is a type of amino acid that has been associated with a long list of health benefits. It was first discovered in 1914 when it was isolated from watermelon, but it wasn’t actually identified until the year 1930.

This important amino acid is integral to the urea cycle, which is a pathway that helps excrete ammonia out of the body through the urine. Like alanine, arginine and glycine, it’s considered non-essential, meaning your body can produce it on its own.

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It can also be found in many different foods and supplements, which can help give your levels a boost to enhance the potential health benefits of this powerful amino acid.

This amino acid plays a key role in several processes within the body. For starters, it helps increase blood flow and reduce blood pressure by widening the arteries.

It also acts similar to nitric oxide supplements to increase levels of nitric oxide in the body, which is a compound that acts as a vasodilator to relax the muscles in the blood vessels and promote circulation. This is because it’s converted into arginine, another amino acid that is used to produce nitric oxide in the body.

Because of its ability to promote proper blood flow, it’s been linked to several possible health benefits. In particular, it is thought to decrease blood pressure, prevent erectile dysfunction (ED) and boost oxygen uptake to optimize exercise performance.

L-citrulline vs. L-arginine

What are the key differences between arginine vs. citrulline?

Both are non-essential amino acids that are necessary for several aspects of health. However, citrulline is actually converted into arginine, which is used to produce nitric oxide, an important compound that helps support better circulation by relaxing the muscles within the blood vessels.

Because of their similarities, L-citrulline and L-arginine taken together is common in supplements geared toward treating conditions like high blood pressure and erectile dysfunction. Interestingly enough, however, some studies have actually found that taking citrulline could increase arginine levels more effectively than arginine supplements alone.

In fact, one of the biggest differences between citrulline vs. arginine is in the way that these two amino acids are absorbed in the body. One study published in Nutrition noted that citrulline is absorbed especially well when taken orally.

Many supplements also combine these important amino acids to help treat issues like high blood pressure and impotence. However, more research is needed to determine the best L-arginine and L-citrulline dosage for ED and other conditions, as well as whether you should take them before bed, with meals or at other times throughout the day.

L-citrulline benefits

1. Helps balance blood pressure

Several promising studies have found a close connection between this amino acid and blood pressure levels. It’s been shown to help improve the function of the cells that line the blood vessels and act as a natural nitric oxide booster.

One study out of Japan showed that taking a citrulline supplement improved endothelial dysfunction and reduced lipoprotein oxidation, which can lead to the development of atherosclerosis, or fatty plaque in the arteries. Another study published in the European Journal of Applied Physiology revealed that taking this amino acid reduced systolic and diastolic blood pressure by 6 percent and 14 percent, respectively.

2. May help treat erectile dysfunction

Erectile dysfunction is the inability to get or maintain an erection, which can be caused by medical issues like high blood pressure as well as mental and emotional issues like stress. Citrulline is one of the most popular natural alternatives to prescription ED supplements thanks to its ability to improve blood flow and decrease blood pressure levels.

A 2011 study conducted by the University of Foggia in Italy found that, although this amino acid was not quite as effective as other prescription supplements for ED like sildenafil, it was able to improve several symptoms of erectile dysfunction after just one month.

In another randomized, double-blind, placebo-controlled, crossover pilot trial published in Sexual Medicine, 20 men with erectile dysfunction who were already using phosphodiesterase type 5 inhibitors (such as Viagra) took 800 milligrams per day of L-citrulline plus 300 milligrams a day of trans-resveratrol for one month, and they showed a significant increase in their Sexual Health Inventory for Men score compared to placebo.

So how long does it take for L-citrulline to work for ED? Although individual results can vary, most people experience symptom improvements within the  first few weeks of starting supplementation.

3. Supports muscle growth

Amino acids like this one are absolutely essential when it comes to muscle growth. Studies show that this important compound stimulates muscle protein synthesis and plays a central role in maintaining protein homeostasis.

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One trial out of Mallorca, Spain, even demonstrated that taking L-citrulline malate could improve the use of branched-chain amino acids during exercise and increase levels of human growth hormone, a type of protein hormone that is thought to improve physical capacity and muscle strength.

4. Can enhance exercise performance

Some research suggests that this amino acid can help improve oxygen usage in the muscles, which can bring some big benefits when it comes to your workout routine. For example, a study in Journal of the International Society of Sports Medicine found that taking this amino acid in supplement form improved physical performance for cyclists and even improved feelings of fatigue and concentration immediately after exercise.

Another study showed that it was effective at enhancing endurance and high-intensity exercise performance by increasing oxygen uptake.

5. May hold antidepressant effects

Emerging research suggests this compound may support mood regulation by influencing nitric oxide production. Studies have found that people with major depressive disorder often have lower circulating levels of citrulline, which may reflect impaired NO synthesis.

Because it is a precursor to arginine and thus may boost nitric oxide generation, it could indirectly help restore endothelial function associated with mood disorders.

In experimental in vitro models, this important amino acid has also shown neuroprotective effects under stress-like conditions (such as glutamate toxicity), potentially helping preserve blood-brain barrier function and support neuronal health.

6. Helps maintain healthy blood sugar levels

Supplementing with this amino acid may contribute to better blood sugar regulation through several mechanisms. In a randomized, controlled trial in people with type 2 diabetes, for instance, three grams of daily L-citrulline for eight weeks significantly lowered fasting glucose, insulin, HbA1c (a long-term blood sugar marker) and markers of inflammation.

Mechanistically, it can inhibit arginase, an enzyme that competes with nitric oxide synthase, which helps preserve arginine availability and boost nitric oxide production. In diabetic patients, L-citrulline has been shown to lower arginase activity and increase nitric oxide levels.

Additionally, it may enhance insulin secretion directly. In cell studies, citrulline has been shown to be metabolized in pancreatic beta cells in a way that stimulates nitric oxide production and promotes calcium signaling, which supports glucose-induced insulin release.

7. May help people with sickle cell disease

One of the promising L-citrulline benefits is its potential in people with sickle cell disease. In a small clinical trial, oral supplementation (given twice daily) raised plasma arginine levels and greatly reduced white blood cell counts, which are often elevated and contribute to complications in sickle cell disease.

This effect likely comes from this amino acid’s role in the arginine-nitric oxide pathway, which promotes vasodilation (widening of blood vessels) and may help reduce endothelial activation and inflammation in sickle cell patients.

Although early data are promising and participants reported improvements in well-being, long-term, large-scale trials are still needed to fully validate its therapeutic role in sickle cell disease.

Foods sources

What foods have citrulline? It can be found in a number of natural food sources, making it easy to meet your needs of this important amino acid by making a few simple switches to your diet.

Some of the top food sources of this amino acid include:

• Watermelon
• Bitter gourd
• Onions
• Garlic
• Nuts
• Chickpeas
• Liver
• Peanuts
• Salmon
• Pumpkin
• Cucumbers
• Gourds
• Squash
• Melons

How to add to diet

There are many different ways to start adding these nutritious foods to your diet. Here are some recipe ideas to help get you going:

• Watermelon aqua fresca
• Garlic baked chicken
• Watermelon salad with rosemary and yogurt
• Fried chickpeas
• Watermelon pizza
• Salmon patties
• Mint watermelon salad
• Cucumber salad with tomatoes and onions
• Watermelon smoothie with strawberries and banana
• Watermelon feta salad

Supplements and dosage

There are two common types of citrulline supplements available: L-citrulline and citrulline malate.

What’s the difference between L-citrulline and citrulline malate?

The main difference between citrulline vs. citrulline malate is the different compounds that they contain. While L-citrulline contains citrulline alone, citrulline malate contains L-citrulline and DL-malate, a compound that aids in energy production during exercise.

How much citrulline should you take a day, and when should I take it?

The L-citrulline dosage can vary based on the type of supplement that you take and the condition you’re trying to treat.

L-citrulline powder has been generally studied in doses of three to five grams per day. The citrulline malate dosage tends to be slightly higher, with a dosage ranging from six to eights grams daily for maximum results.

The L-citrulline dosage for ED may be a bit lower, with doses ranging between 1.5 to three grams per day.

There are no specific guidelines for citrulline malate dosage timing, but it’s recommended to take it around one hour before exercise if you’re looking to increase muscle recovery and endurance. For other conditions, you can split your supplement into several smaller citrulline dosages, which can be taken with meals throughout the day.

Risks, side effects and interactions

In most cases, this important amino acid is safe, effective and associated with very few L-citrulline side effects. In fact, one study out of Paris relayed that taking even high doses up to 15 grams per day was safe and well-tolerated by participants.

Women who are pregnant or breastfeeding should avoid supplementation to prevent any potential citrulline side effects. It’s also not recommended for those taking other medications like nitrates for high blood pressure, heart disease or erectile dysfunction.

Taking it in combination with these medications can cause dangerous drops in blood pressure, which could potentially be harmful.

Therefore, it’s best to talk to your doctor before starting supplementation if you are taking any medications or have any underlying health conditions. Additionally, be sure to use only as directed to prevent any adverse effects on health.

Frequently asked questions

What is L-citrulline good for?

It is best known for supporting healthy blood flow, exercise performance, energy and cardiovascular function. One of the biggest L-citrulline benefits is its ability to boost nitric oxide production, which helps relax blood vessels, promote better circulation and enhance oxygen delivery to muscles. This is why it is commonly used for workouts, muscle pumps, recovery and overall heart health.

Is L-citrulline good for erectile dysfunction?

Yes, research suggests that L-citrulline benefits include potentially helping mild to moderate erectile dysfunction because it increases nitric oxide, which supports healthy blood flow to the pelvic area. While it’s not considered a replacement for ED medications, it may offer a natural option for improving firmness and performance, especially in men with poor circulation.

Is it safe to take L-citrulline every day?

For most people, L-citrulline is considered safe to take daily when used at recommended dosages. Most studies use between 2,000-6,000 milligrams per day, depending on the goal. As with any supplement, people with cardiovascular conditions, low blood pressure or those taking blood pressure medications should speak with a healthcare provider before regular use.

What happens if you take L-citrulline every day?

Daily L-citrulline may help improve blood flow, support workout performance, enhance recovery and maintain healthier vascular function. Many people notice better stamina, reduced muscle soreness, improved strength and more consistent energy levels. Some men also report improvements in erectile function due to the L-citrulline benefits for circulation.

Which is better, L-arginine or L-citrulline?

L-citrulline is generally considered more effective than L-arginine for boosting nitric oxide. Although L-arginine is the direct precursor to nitric oxide, the body absorbs L-citrulline more efficiently, allowing it to raise arginine levels more reliably. As a result, L-citrulline benefits, such as enhanced blood flow and performance, tend to be stronger and more consistent compared to L-arginine.

Is L-citrulline good for testosterone?

L-citrulline is not a testosterone booster, but it may indirectly support male performance by improving blood flow, energy and exercise capacity. Better circulation and improved workout output can support healthy hormone balance overall, but citrulline itself does not directly increase testosterone levels in studies.

What are the disadvantages of citrulline?

Citrulline is generally well-tolerated, but possible disadvantages include digestive discomfort, especially at higher doses, as well as potential interactions with blood pressure medications or erectile dysfunction medications, since it naturally enhances blood flow. Some people may also experience headaches or lightheadedness due to blood vessel dilation. Starting with lower doses can help minimize side effects.

Does citrulline increase muscle pumps?

Yes, one of the most noticeable citrulline benefits during workouts is a stronger “pump.” Because citrulline benefits nitric oxide production, it enhances blood flow to active muscle groups, which can increase vascularity, performance and endurance.

How long does it take for L-citrulline to work?

Most people feel the effects within 30 to 60 minutes, especially for exercise performance. For cardiovascular or circulation-related benefits, consistent daily use for several weeks may provide best results when it comes to L-citrulline benefits.

Can you take citrulline on an empty stomach?

Yes, it is typically well-tolerated on an empty stomach and may even absorb better this way. However, people with sensitive digestion may prefer taking it with food.

Final thoughts

• What is L-citrulline? It is an important non-essential amino acid that plays a key role in several aspects of health.
• It’s converted into arginine in the body, which is used to make nitric oxide, a compound that helps dilate and relax the blood vessels to promote proper circulation.
• Potential L-citrulline benefits include decreased blood pressure, increased muscle growth and improved exercise performance. Citrulline malate benefits certain health conditions like erectile dysfunction as well, thanks to its ability to increase blood flow through the body.
• Although it’s generally safe and associated with very few side effects, it’s not recommended for those taking nitrates or medications for high  blood pressure, heart disease or erectile dysfunction, as well as women who are pregnant or breastfeeding.