Nitric Oxide Gets Blood Flowing
At last, a gas that everyone is glad to have. The biological gas nitric oxide (NO) lowers blood pressure, improves blood flow and blood vessel diameter, and is derived from the amino acid L-arginine. When nitric oxide is formed through an enzymatic reaction in the body, an even more useful amino acid is formed: L-citrulline. The body can recycle L-citrulline back into L-arginine, which can then be converted back into nitric oxide—and more NO is a yes for the body. Though L-citrulline is an amino acid, it is not found in the proteins we consume, but it is produced in notable amounts by the liver and intestines from other amino acids.

Now, scientists think that L-citrulline itself may serve as a blood vessel/pressure regulator, and an even more efficient modulator than L-arginine. A study on rats found that L-citrulline—by recycling back into L-arginine—produced substantial relaxation of blood vessels and increased the production of nitric oxide.

Research has suggested that L-citrulline may be a more efficient way to get more L-arginine to the body, even better than consuming it directly, since dietary L-arginine is not readily absorbed. L-citrulline is credited not only with enhancing blood flow, but also for improving erectile function and reducing symptoms of sickle cell anemia. Systematic evaluations of this theory will soon begin.

Nutrition and exercise biochemist Anthony Almada, MS, has collaborated on more than 45 university-based studies, is co-founder of Experimental and Applied Sciences (EAS) and founder and chief scientific officer of IMAGINutrition (