What is L-citrulline?
L-citrulline is a non-essential amino acid, which means the body already produces it naturally. Glutamine is the most abundant amino acid in the body, primarily producing L-citrulline.
Unlike many amino acids you may have heard of, L-citrulline is not used to make protein. Instead, it has other functions in the body.
L-citrulline participates in the urea cycle, where toxic ammonia is converted into urea. Ammonia is produced by bacteria and cells in the gut when they process proteins. Converts ammonia into urea, which is excreted in the urine.
L-citrulline aids in the formation of nitric oxide (NO). NO plays a role in vasodilation. It also helps release certain hormones, such as growth hormone and insulin.
What are the benefits of L-citrulline?
L-citrulline has a variety of benefits, including:
Exercise and sports performance
One of the main benefits of L-citrulline is that it can enhance exercise or sports performance. It does this by affecting the production of nitric oxide (NO).
The production of NO causes the breakdown of arginine into L-citrulline and NO. But L-citrulline is also a precursor of arginine. The body converts approximately 80% of citrulline into arginine.
Supplementing with L-citrulline increases arginine, which increases nitric oxide levels. Higher nitric oxide levels may lead to increased blood flow, which means your tissues receive more oxygen and nutrients.
According to some studies, L-citrulline can help increase oxygen uptake and muscle oxygenation. A 2021 study in rats found that taking L-citrulline orally increased levels of various substances delivered to muscles.
Small studies have found that taking L-citrulline supplements can improve aerobic exercise performance, specifically cycling and weightlifting.
The National Institutes of Health (NIH) says research on using L-citrulline to improve athletic performance is limited and conflicting. A recent review found that L-citrulline did not show any benefits in aerobic exercise or endurance performance.
As mentioned before, L-citrulline helps make NO. NO causes blood vessels to dilate. This can help lower blood pressure.
A 2019 review found that L-citrulline's blood pressure-lowering effects are unclear. It shows that L-citrulline reduces systolic blood pressure by 4.1–7.5 mmHg (millimeters of mercury) and diastolic blood pressure by 2.08–3.77 mmHg.
Another 2019 review looked at eight studies where researchers were looking at L-citrulline's effects on blood pressure. They found that lower doses of L-citrulline supplements reduced systolic blood pressure.
A 2018 review of studies showed that L-citrulline supplements did not help lower blood pressure.
Nitric oxide causes blood vessels to dilate, resulting in increased blood flow, including to the genitals. L-citrulline supplements may help treat erectile dysfunction (ED).
A small 2011 study found that taking 1.5 grams of L-citrulline daily for a month improved the ability of men with ED to maintain an erection.
However, L-citrulline is still less effective in treating ED than phosphodiesterase type 5 inhibitors such as sildenafil (Viagra) and tadalafil (Cialis).
What foods contain L-citrulline?
Watermelon is a major food source of L-citrulline. According to the NIH, researchers found that one cup of diced seedless watermelon contains about 365 milligrams of L-citrulline.
L-citrulline concentration depends on the specific type of watermelon. A 2019 study noted that Crimson Sweet and Dixielee varieties of watermelon contain high levels of L-citrulline.
Other foods have much lower levels of L-citrulline than watermelon. Some examples of other foods containing L-citrulline include:
- Other types of melons
Can you take L-citrulline supplements?
L-citrulline is available as a supplement. It usually comes in powder or capsule form.
There is no standard recommended daily dosage for L-citrulline.
The NIH noted that research found that non-athletes taking 6 grams of L-citrulline daily for four weeks showed no adverse effects.
More extensive research will determine the safety of L-citrulline, especially if you take the supplement for several months at a time.
Earlier research showed that study participants could tolerate up to 15 grams of L-citrulline for up to 8 hours without side effects.
Supplements containing L-citrulline come in two forms: citrulline and citrulline malate. Citrulline Malate is a 56.64% trusted source of citrulline. This means that 1 gram of citrulline malate contains slightly more than 0.5 grams of citrulline.
Who needs to avoid L-citrulline supplements?
Research reports some side effects of L-citrulline supplements. The National Institutes of Health notes that some people who take L-citrulline may experience stomach upset.
But research is unclear whether these supplements are safe and effective.
L-citrulline may also interact with certain prescription medications, such as:
- blood pressure medication
- erectile dysfunction drugs
However, L-citrulline may interact with some prescription medications, such as those that treat high blood pressure, cardiovascular disease, and erectile dysfunction.
Before starting any new supplements, consider talking to your doctor first. They can provide advice on whether a specific supplement is suitable for you.
Your doctor can recommend a dose of L-citrulline that's right for you and discuss side effects or drug interactions.
L-citrulline is a non-essential amino acid that has multiple functions in the body. You can use it as a supplement.
L-citrulline supplements may have a variety of health benefits, including improving athletic performance and lowering blood pressure. However, research into these areas is still limited, and more extensive research would help us better understand the benefits.
Although research is unclear whether L-citrulline is safe, it has shown some side effects associated with L-citrulline. Drug interactions may occur, so consult your doctor. They can tell you whether L-citrulline supplements are right for you and what dosage you should take.