L-Citrulline: Benefits, Side Effects & Dosage
What is L-Citrulline? L-citrulline is a dietary amino acid that plays a role in the urea cycle, along with L-
arginine and L-ornithine. The body produces it naturally in the liver and intestines from 90 percent L-glutamine (x). Since it is a non-essential amino acid, one does not have to take it in through their diet. In reasonably high levels, though, it is quite beneficial in improving body function, performance and overall health.
L-citrulline was originally discovered in large amounts in watermelon (x). It was then named after the Latin word ‘Citrullus’ for watermelon. The amino acid is also present in a few other foods such as squash, pumpkins, cucumbers and melons (x, x).
Unlike the majority of amino acids present in the body, L-citrulline is not a building block for proteins (x). It converts to nitric oxide and L-arginine, which plays a very crucial role in the urea cycle; it helps the body get rid of ammonia and other toxic compounds in the ammonia cycling process. Moreover, it boosts nitric oxide metabolism, which makes it useful in treating erectile dysfunction, especially that caused by athletic activity and high blood pressure.
How it Works When one ingests L-citrulline, the kidneys convert it to amino acid arginine, which later converts to nitric oxide molecules in a process called nitric oxide synthase. It releases them into the bloodstream, and they circulate in the entire body. These smooth out the cells of the blood vessel walls and ease constriction, effectively leading to vasodilation (x). This is when the blood vessels widen, causing a reduction in blood pressure.
Nitrogen oxide molecules are attributed with many of the benefits of taking the supplement, such as correcting erectile dysfunction and good heart health (x).
L-Citrulline and L-Arginine Supplements As science would have it, L-citrulline supplements are better at producing arginine than L-arginine supplements themselves. The latter only lasts a short time in the body (x).
Many prefer L-citrulline supplements as the body easily ingests them (especially Lcitrulline powder) with no side effects. L-arginase, on the other hand, comes with side effects such as stomach upsets, diarrhea, nausea and vomiting.
When taken together, however, the two produce nitric oxide levels that would not be achieved on their own (x).
Types of L-Citrulline Supplements There are two significant types of citrulline:
â—? L-citrulline, which is the pure supplement without any additives. â—? Citrulline malate, which is a combination of the amino acid and another compound (malate). It is efficient in energy production, which is why many use it for exercise and athletic activity (x).
More research is necessary to determine the similarities and differences between L-
citrulline versus L-citrulline DL-malate benefits.
L-Citrulline Benefits L-Citrulline for Blood Pressure As mentioned earlier, the breakdown process of L-citrulline to L-arginine also produces nitric oxide, which is quite helpful in reducing blood pressure in the body. It works by increasing the dilation of blood vessels, therefore reducing the pressure of blood flow.
Two studies were conducted on 12 young men. The amino acid effectively reduced both systolic and diastolic blood pressure in each of the subjects (x, x).
Other studies were conducted on 30 to 40 adults who had high blood pressure or heart conditions. After eight weeks, the researchers found that L-citrulline reduced their blood pressure by five to 15 percent (x, x).
Studies in healthy individuals, however, have not shown any significant results. Researchers found little or no changes in individuals participating in the experiments between one to four weeks (x, x). Therefore, it remains unclear whether healthy individuals stand to gain this benefit from taking L-citrulline supplements.
Boosts Athletic Performance
Citrulline widens the blood vessels, which improves blood flow. Owing to this property, it has been studied for any benefits it may offer in improving exercise, particularly in strength training and endurance exercise.
Strength Training These tests used citrulline malate.
Forty-one men were studied for any improvements in weight training on their upper bodies after taking the supplement an hour before their exercise. They were able to increase their normal reps by 53 percent compared to those who were placed on a placebo (x).
There was also a drastic reduction in muscle soreness (by up to 40 percent) two days after the exercise.
Endurance Exercise A study observing cyclists found that those taking L-citrulline were able to cycle for up to 12 percent longer before exhaustion, compared to those placed on a placebo (x).
Generally, just one dose of the supplement does not produce any significant results in endurance exercise (x). Taking them for one to four weeks will increase the content of oxygen in the muscles without changing the rates of its consumption (x, x).
Another study on 30 people with heart failure further proves its potential as an endurance booster. Those who took the supplement before exercise were able to exercise for longer than those placed in placebo (x).
Erectile Dysfunction In Italy’s University of Foggia, a study to test the effect of L-citrulline on erectile dysfunction was conducted among 24 men, all past the age of 55. They were all diagnosed with mild erectile dysfunction and split into two groups; one took 1.5g of Lcitrulline each day for a month, and the other took a placebo.
At the end of the study, about 50 percent of the men taking the supplement gained normal erections and significantly increased their frequency of sexual intercourse (x).
Another study in Japan involved three groups of 15-week old rats. When the castrated group took the supplement, their erectile response improved significantly (x).
Boosts the Immune System In Spain, a laboratory conducted a study on 17 professional male cyclists to determine the effect of oral L-citrulline on the immune system. The men split into two groups; the first was the control, and the second took doses of the supplement.
Blood samples collected twice after the race showed that the L-citrulline increased the concentration of plasma when taken before the exercise (x).
It is particularly beneficial as neutrophils, an-infection-fighting type of white blood cells. This experiment, however, only used oral L-citrulline.
L-Citrulline Side Effects A study to test any possible side effects of L-citrulline was performed on a group of men who were administered with 2g, 5g, 10g and 15g. There were no side effects present in any of them (x). A follow-up analysis was done on blood samples taken from these subjects, and there were no deviations from the normal body functioning, including the blood pressure.
There have been only a few cases where patients reported mild stomach discomfort after taking the supplement (x). That aside, it would be safe to say that L-citrulline has no serious health effects.
It has been observed that high levels of the amino acid supplement do not increase arginine levels in the body, which suggests that there is a limit for maximum production of arginine, beyond which there is no significant increase. Scientists advise not taking more than 10g of it.
More research, however, is necessary to confirm the long-term effects of taking the supplement in high doses.
Drug Interactions It is advisable to avoid L-citrulline if you are taking any of the following medications:
● Drugs for erectile dysfunction such as Viagra and Levitra ● Nitrates for heart disease ● Medicines to treat high blood pressure ● Any drugs to treat any form of heart disease
Risks It would be safe to make thorough consultations with a professional health practitioner, or avoid L-citrulline if you are pregnant, breastfeeding or taking any of the medications mentioned above.
Remember to consult your doctor and keep them updated on any supplements you want to take so that he/she can advise you accordingly. Other factors could be important in determining the safety of taking these drugs, such as your medical history, illnesses or even inherited conditions from your family. Also, do not self-diagnose yourself for any condition. Supplements are meant to boost your health and not treat illnesses.
L-Citrulline Supplement L-Citrulline Dosage and Instructions These supplements are neither endorsed or regulated by the FDA, which leaves it to the manufacturers to suggest the best dosage for their products.
Research, however, suggests that an average adult should take a dose of 3g to 6g of
citrulline per day, and about 8g of citrulline malate. As mentioned earlier, the body has a limit beyond which any additional L-citrulline will not produce any supplemental arginine. This is thought to be 10g, and doses beyond this may not cause any stomach upsets or some of the other side effects experienced with other amino acid supplements. This is probably because L-citrulline in food or supplement is absorbed and processed more quickly than other amino acids (x).
Here are some recommendations for the following uses:
To Reduce Blood Pressure The optimal doses would be between 3g and 6g. This, of course, may also depend on other factors such as the severity of hypertension and other drugs one is taking for the same cause. Always consult a doctor before taking it.
To Boost Oxygen Levels in the Muscles To increase the volume of oxygen in the muscles, it is advisable to take 6g or more for at least a week. This, again, may also depend on several factors, such as the intensity of exercise and physical factors (x).
L-Citrulline for Bodybuilding 4.5g of citrulline would do just fine for effective performance, and that equals to 8g of citrulline malate (x).
Erectile Dysfunction Your doctor should help you work out a suitable dosage. 1,500mg of L-citrulline is recommendable.
Endurance Training 2,400mg of the supplement daily would be useful in reducing fatigue and increasing capacity for exercise before complete exhaustion.
For Heart Failure As per clinical trials, 3,000 mg of the supplement daily should be sufficient enough to reduce complications that result from heart failure.
The Bottom Line L-citrulline is a non-essential and non-building amino acid that is found in watermelons and other foods. It is extracted as a supplement and taken for health benefits such as reducing high blood pressure, correcting erectile dysfunction, minimizing complications of heart failure and boosting the immune system. L-citrulline is also essential in increasing oxygen in the muscles, which boosts exercise and athletic performance as well as reducing fatigue and muscle soreness.
While there are no apparent side effects of taking citrulline in both optimal and high doses, the body can only convert up to 10g of it into arginine and nitric oxide. The
supplement may interact negatively with drugs such as those for reducing blood pressure and correct heart disorders. Pregnant and breastfeeding women should avoid it or consult with their doctors before taking it.
The FDA does not regulate L-citrulline supplements, and there is no standard dosage. Scientists, however, recommend a dose of between three and six grams daily for an average adult. This, however, may vary depending on the purpose and other factors such as the health of the individual.