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What is L-Citrulline & What Does It Do?

Citrulline is an amino acid that is produced naturally in the human body. It is also found in some types of food and it is widely available as a dietary supplement. In this article, we’ll take a look at some of the scientific facts about L-citrulline and learn more about the many benefits it has to offer.

Citrulline melate for fitness

Background Information About L-Citrulline

L-citrulline is an amino acid normally made by the human body. L-citrulline is considered a by-product of nitric oxide (NO) synthesis. The body converts L-citrulline to L-arginine, another type of amino acid. L-arginine improves blood flow. It does so by creating nitric oxide, a gas that helps dilate your blood vessels. L-arginine has been shown to help people with heart disease or clogged arteries because of its vessel-widening abilities.

Increasing your intake may also have beneficial effects on health and exercise performance. Citrulline may increase blood flow by increasing nitric oxide production. It may also produce positive effects on muscle by stimulating protein synthesis and decreasing amino acid breakdown. Based on current information, citrulline is safe and well-tolerated. However, doses of greater than 10 grams are probably unnecessary.

The same effect on blood vessels helps improve symptoms of erectile dysfunction (ED). As we will explain later, the L-citrulline to NO path increases blood flow to a man’s genitals. In one study, this  increase in blood flow appeared to decrease symptoms of mild ED and improve a man’s ability to maintain his erection. At this point in time, there have not been any studies on the use of L-citrulline in moderate to severe cases of ED. However, it has been found that oral l-citrulline supplementation improves erection hardness in men with mild erectile dysfunction.

When citrulline is taken in conjunction with a multivitamin such as our  VITAE Men’s Health Optimizer, it can lead to some noticeable benefits. VITAE was meticulously designed to amplify your performance in the office, gym, and in the bedroom. VITAE features full spectrum multivitamin, greens and superfood complex, and hormone optimizing compounds. Together with a nutritious diet, all of these ingredients can greatly improve your overall performance.

L-Citrulline 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. Some of the foods that are known to contain citrulline include: 

  • Watermelon 
  • Pumpkins 
  • Cucumber 
  • Melon
  • Gourds 

To get more L-citrulline in your diet, watermelon can be one of the best foods you can eat. Most legumes, meat, and various kinds of nuts also contain smaller quantities of the amino acid. But most people use supplements to increase the amount of L-citrulline in their diets. 

Citrulline is considered a non-essential amino acid, meaning that your body can naturally produce some on its own. However, you can increase your levels by eating foods like those listed above, rather than relying on your body’s production alone. Higher levels of L-citrulline may produce some real beneficial effects on health and exercise performance, as discussed later in this article. 

Citrulline plays some important roles in the human body, but unlike some amino acids, it is not used to build proteins. It does play 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 the form of urine. Both L-citrulline and L-arginine accelerate urea cycle enzymes, which can promote proper ammonia removal.

L-citrulline supplements are generally available over the counter. But few credible FDA or peer-reviewed studies have looked at the proper dosing for L-citrulline, so there are no official dosing recommendations. However, one study from the British Journal of Nutrition found that  doses between 2 and 15 grams (g) were safe and well-tolerated by the study’s participants. 

Supplements that are readily available in most stores generally range from 500 milligrams (mg) to 1.5 grams. Some supplements contain a mixture of L-citrulline and other ingredients, so always read the supplement label to see exactly how much of the amino acid you are taking with each type of supplement.

Should You Take Citrulline Supplements?

Citrulline is gaining popularity as a supplement to improve health and exercise performance, because taking supplements increases the citrulline content in your body. While some people are convinced of its effectiveness, others are more skeptical. This section will discuss everything you need to know about citrulline supplements and whether you should take them. 

L-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, which is associated with lower blood pressure and increased blood flow. 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.

Consuming citrulline may actually increase the arginine levels in your body more than simply consuming arginine by itself. This is because of differences in how the body processes and absorbs arginine and citrulline. The increase in nitric oxide and blood flow may be one of the reasons citrulline has 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. Citrulline may also reduce the liver’s uptake of certain amino acids and prevent their breakdown. Through these dual effects on protein synthesis and amino acid breakdown, it may help you maintain or increase your muscle mass.

Types of Citrulline Supplements 

There are two major forms of citrulline in dietary supplements. The first is simply known as l-citrulline, which refers to citrulline by itself, with nothing else attached. The second is citrulline malate, which refers to the combination of citrulline and another compound called malate, which is important for energy production. While these 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. 

Major Health Benefits 

Researchers have looked into the potential health effects of l-citrulline, including some of the effects it has on blood vessels, the effects it has on blood pressure, the effects it has on erectile dysfunction, and the effects it has on overall exercise performance across a wide range of activities. 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.

However, when people who have heart disease consumed L-citrulline for seven days or longer, the ability of their arteries to widen improved. So, although a single dose may not be very effective at widening your blood vessels, taking supplements over a longer term may prove more effective. Citrulline supplements may decrease blood pressure. Several studies have examined the effects of citrulline supplements in adults with high blood pressure (hypertension) or other heart conditions. They found that the blood pressure of their participants was reduced by up to 15% after eight weeks.

Another small study examined 12 adults with normal blood pressure, and it was found that citrulline reduced blood pressure by up to 16% after a week. However, the evidence in healthy individuals is not conclusive. Overall, it is unclear if it substantially affects blood pressure in healthy individuals. The research to support the use of L-citrulline as an ED treatment is quite limited. Treatment with traditional ED medications (the phosphodiesterase type 5 inhibitors Cialis, Levitra, and Viagra) has proven to be very effective, but some men prefer not to use those medications because of possible risks or side effects.

This may be true especially for men who experience only mild erectile dysfunction. In those cases, the use of L-citrulline may be preferable, at least for short periods of time. L-citrulline is believed to be safe, as studies haven’t yet found any known side effects. However, there has been no large randomized clinical trial to assess the safety of L-citrulline for ED treatment. If you are taking any other medications, it’s important you talk with healthcare professionals about possible side effects. 

This is especially important if you are taking any other medications that also work to dilate your blood vessels, ​​or medications such as nitrates that increase the blood flow to your heart. L-citrulline supplements may have additional synthetic ingredients similar to traditional ED medications. Simultaneous use of L-citrulline supplements with other vasodilatory drugs can cause dangerous drops in blood pressure.

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. Citrulline also has a beneficial effect on the quality of sleep that you get each night, especially when it is taken as a supplement together with a product like our  SANA Deep Sleep Formula.

Endurance Exercise in Aerobic Activities

In general, a single dose of citrulline does not seem to improve overall endurance exercise athletic performance very much. Taking supplements for up to two weeks does not even change a person’s oxygen consumption. However, it can increase the oxygen content in muscle tissue. This means that although it may not allow more oxygen to be used by the body as a whole, it can improve oxygen usage in the exercising muscle, which may ultimately lead to better exercise performance.

This effect has been demonstrated in cycling, where performance can be increased by taking citrulline supplements. Some cyclists taking citrulline have been able to cycle for up to 12% longer before exhaustion than those taking a placebo. Taking these supplements for seven days can also improve your power output during your next cycling session. Overall, a citrulline supplement may beneficially affect oxygen usage in muscle, which is something that will greatly improve your endurance. 

Closeup of a muscular young man lifting weights on dark background

Weight Training 

Several studies have shown that citrulline malate can improve weight training performance. One study assessed the effects of citrulline malate on the ability to  perform repetitions during upper body exercise. Participants were able to perform greater than 50% more repetitions (reps) after they ingested citrulline malate, as compared to a placebo group.

That same study found that the amount of muscle soreness in the two days after exercise was 40% lower when the participants consumed citrulline malate before doing their exercises. Other researchers also found that l-citrulline malate can decrease fatigue and increase lower body weight training performance. In both of these studies, participants were instructed to take the supplement about an hour before they started exercising.

What is the Recommended Dosage?

Based on current research, a recommended dose is up to 6 grams per day of L-citrulline or approximately 8 grams per day of citrulline malate for most people. The dose varies depending on form because 1.75 grams of citrulline malate provides 1 gram of L-citrulline. The remaining 0.75 grams are malate. 

For people who are specifically focused on weight training, eight grams of citrulline malate provide about 4.5 grams of citrulline, an effective dose for weight training performance. To improve the amount of oxygen in your muscles, taking 6 or more grams of L-citrulline per day for seven days seems to be quite effective.

For those who want to lower their blood pressure, the daily dose of L-citrulline used in research is between 3 and 6 grams a day. Furthermore, doses of 10 or more grams do not typically cause an upset stomach, unlike other amino acids. In fact, L-citrulline may help treat intestinal problems. This is great news if you are taking the supplement to boost your exercise performance. Citrulline is probably better tolerated by most people due to differences in how it is absorbed and processed compared to other amino acids.

Health Concerns and Side Effects 

Unlike many supplements, some preliminary information about citrulline’s safety at higher doses 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 when taken at 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 in participants after they took citrulline supplements did not show any negative changes to normal body functions or blood pressure. 

An Overview of L-Citruline

Due to its impressive ability to increase the amount of blood flow in the human body, citrulline has been studied within the context of both endurance and strength-based types of exercises. Several studies of endurance exercise have focused on L-citrulline, while much of the strength-based research continues to use the form of citrulline malate. A dose of 8 grams may reduce fatigue and improve your performance in the gym. 

Final Verdict

So, citrulline can be considered an amino acid that offers several health benefits. It also appears to be safe and there are currently very few known side effects. In supplement form, it may boost your immune system, promote healthier blood vessels, and lower your blood pressure. If you want to lower your cholesterol levels, improve your heart health and reduce your risk of cardiovascular disease, or simply improve your overall exercise performance, citrulline may be the type of supplement you should be considering.

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