Isolated in watermelon in 1914 by two Japanese chemists, citrulline is an amino acid synthesized by the human body and plays an important role in the urea cycle. But it is its use as a supplement in the context of sport that has become more popular in recent years. Indeed, many studies have shown the beneficial effects of citrulline on certain physical functions such as vasodilation and muscle development, making it a supplement of choice in the context of physically rigorous activities such as weight training.
Citrulline is an amino acid first discovered in watermelon. It is considered non-essential, which means the body can naturally produce it on its own. However, it is possible to increase citrulline levels by eating foods containing citrulline or taking dietary supplements.
These higher levels produce beneficial effects on health and physical performance; especially in the context of sports training and bodybuilding. Citrulline plays an important role in the body, but unlike some amino acids, it is not used to make proteins. Citrulline can also help widen blood vessels and plays a role in muscle development. This is why the benefits of citrulline for muscle training are often touted.
Citrulline produces several important effects in the body. In particular, it increases vasodilation. Vasodilation refers to the widening of arteries or veins. It is associated with lower blood pressure and increased blood flow. Once citrulline is consumed, some of it is converted into another amino acid called arginine.
Arginine is converted into a molecule called nitric oxide, which causes blood vessels to vasodilate by relaxing the smooth muscle cells that constrict them. The increase in nitric oxide and blood flow is part of the process involved in the beneficial effects of citrulline on physical performance.
Although citrulline is not an amino acid used directly to synthesize protein, it has been shown to increase protein synthesis by stimulating an important signaling pathway involved in building muscle. Thanks to this double effect on protein synthesis and the breakdown of amino acids, it contributes to maintaining and increasing muscle mass.
Citrulline therefore works primarily in bodybuilders by helping to promote vasodilation. Widening blood vessels help increase the amount of nutrients and oxygen delivered to working muscles. This helps promote better performance, greater cellular energy production, better post-workout recovery, and improved muscle fiber condition once the workout is over.
Citrulline supplementation may also help promote better blood flow to the brain. Such a blood flow improves the athlete's cognitive pathways, thus improving their ability to adapt, plan and concentrate. Citrulline can thus replace pre-workout caffeine supplements.
Unlike many supplements, some preliminary safety information for citrulline at higher doses is available. One study looked at different doses in eight healthy men. Each participant consumed doses of 2, 5, 10, and 15 grams of L-citrulline on separate visits.
Even with the highest doses, participants reported no side effects. However, the higher doses did not seem to increase blood arginine as much as expected, which means there is a limit to how much of this supplement your body can use.
Overall, the study indicated that doses above 10 grams are unnecessary. Blood work done on participants after taking citrulline supplements showed no negative changes in normal bodily functions or blood pressure.
