What is L-citrulline good for?
L-citrulline is one of many amino acids that our body uses, and we also produce it ourselves, which makes it a non-essential amino acid.
However, unlike most amino acids, which are used in various combinations by the body to form assorted proteins, L-citrulline does not form a part of the protein-building process, and is instead involved in the urea cycle, which means that it assists in the detoxification and excretion of harmful substances through the urine.
L-citrulline for improved circulation
L-citrulline is also converted into L-arginine within the kidneys, which is a precursor to nitric oxide, an important substance that helps dilate blood vessels and improve circulation. In fact, most supplements that describe themselves as "nitric oxide boosters" are primarily composed of both L-citrulline and L-arginine.
L-citrulline for blood pressure
These properties are also thought to make L-citrulline a potential candidate for treating high blood pressure, as there is a growing body of research with multiple studies demonstrating L-citrulline's capacity to significantly lower blood pressure through daily supplementation of between 3g and 8g over the course of several months.
L-citrulline for athletic performance
It is also thought that the resulting increase in nitric oxide production from L-citrulline supplementation offers benefits in other areas, such as muscle function and athletic performance, simply by increasing blood flow to the muscles. Most research seems to suggest that these benefits are more pronounced in strength training rather than aerobic training.
That said, one study involving cyclists found that by taking 2.4g of L-citrulline daily in the week leading up to an event, participants were able to increase their exertion and also feel less exhausted after cycling 4km (roughly 2.5 miles).
Another study found that by taking 6g of L-citrulline daily for seven days, participants could exert themselves harder and for longer on a severe-intensity exercise test.
When should I take L-citrulline?
L-Citrulline can be taken at any time of day, with or without food, however it is most often recommended to be taken on an empty stomach in order to maximize absorption.
For taking advantage of it's benefits for physical performance, you will want to incorporate it into your pre-workout routine, optimally taking it between 30 and 60 minutes before exercise.
What does L-citrulline combine well with?
L-citrulline with L-arginine, for nitric oxide production
As mentioned above, L-citrulline has the capacity to increase the level of nitric oxide in your blood, which serves to dilate blood vessels, increasing circulation and reducing blood pressure. This is achieved by the way in which L-citrulline is converted in the kidneys into L-arginine, a precursor to nitric oxide.
These effects are enhanced even further when L-citrulline supplementation is combined directly with L-arginine supplementation, and both of these amino acids are frequently found together as the primary ingredients for nitric oxide boosting supplements.
What are natural sources of L-citrulline?
If you are interested in achieving your daily L-citrulline intake through your diet, rich sources of L-citrulline include:
- Watermelons
- Melons
- Cantaloupes
- Squash
- Pumpkins
- Cucumbers
- Parsley
- Fennel
- Lettuce
L-Citrulline data sources & further reading
Last updated by Asklepios on 30th January, 2025