In short, some of L-citrulline will be converted to arginine and boost the production of nitric oxide and nitric oxide helps our arteries to relax (smooth muscle cells in blood vessel) resulting oxygen rich blood circulating through arteries and work better in terms of improving blood flow throughout our body, we called it vasodilation. Why don’t we take L-arginine you ask? Well, interestingly, consuming citrulline may increase arginine in the body more than consuming arginine itself, we will discuss about this further. Other than that, it is also associate with lower blood pressure. Imagine there is no traffic jam in highway, Smooth! Besides, people also take L-citrulline for improving athletic performance. Citrulline has important roles in our body, but unlike for other amino acids, it is not used to build proteins. Although it is not directly use to build proteins, it has been shown to increase protein synthesis by stimulating signalling pathway involved in muscle building. That’s why you can see citrulline in various muscle building supplement range especially for pre-workout supplements. Furthermore, it plays a necessary part in urea cycle, especially removing ammonia from our body as it increases plasma level of ornithine and arginine and improve ammonia recycling process and nitric oxide metabolisms. In addition, citrulline may reduce the liver’s uptake of certain amino acids and prevent their breakdown.
There is evidence show that L-citrulline supplement may help to lower blood pressure in people with elevated blood pressure. Elevated blood pressure increases the risk for high blood pressure and heart disease.
Let’s dive down a little bit. Oral L-arginine undergo significant breakdown occurs by enzyme arginase in our gastrointestinal pathway that hydrolyses arginine into ornithine and urea. This result in low plasma L-arginine levels and reduced bioavailability of L-arginine as a substrate for endothelial nitric oxide synthesis (eNOS). L-citrulline itself is a precursor arginine, either natural or synthetic citrulline can be converted into arginine effectively in the urea cycle. Unlike L-arginine, dietary L-citrulline is not broken down by arginase and bypasses liver uptake and degradation. It has been shown that L-citrulline is an inhibitor of arginase. Therefore, it can be said that L-citrulline is a more efficient intervention for increasing L-arginine bioavailability and nitric oxide production than oral L-arginine.