New Research Finds Applications for L-Citrulline

Evidence from Kyowa Shows Benefits beyond Nitric Oxide Production Through Citrulline Supplementation 

NEW YORK CITY, NY (May 22, 2013) – New research from Kyowa Hakko Bio shows that L-citrulline is 1.6 times more effective at elevating plasma L-arginine levels than taking arginine alone. New findings using data from rat subjects also associate citrulline supplementation with reduced sensitivity to cold by increasing blood flow to the skin. The research will be presented next week by Dr. Darryn Willoughby at the International Society of Sports Nutrition (ISSN) Conference and Expo in Colorado Springs on June 14-15, 2013.

Nitric Oxide (NO) is a key molecular and cellular messenger in the body that, among other biological processes, is used to increase blood flow in the body through dilation of blood vessels. Arginine, a precursor to NO, has long been the standard means of triggering increased production of NO in the body. The new research suggests citrulline may be a more effective way of elevating arginine levels and NO in the body.

“The importance of L-citrulline for ergogenic support is because L-citrulline is not subject to pre-systemic elimination and could be a more efficient way to elevate extracellular L-arginine levels,” said Dr. Darryn Willoughby, an ISSN Fellow and Associate Professor of Exercise and Nutritional Biochemistry and Molecular Physiology at Baylor University. “Preliminary research with oral L-citrulline has shown elevated plasma L-arginine concentration and augmented NO-dependent signaling.”

Along with vitality benefits such as improved circulation and reduction in sensitivity to cold, this new evidence opens new doors for citrulline application in heart health as well. A short-term citrulline supplementation could functionally improve atrial stiffness in humans by increasing vascular relaxation and increasing blood flow to the body. 

Citrulline also may find new applications in the muscle building, fatigue relief and energy markets considering the link between NO production and athletic performance. “Compared to L-arginine, L-citrulline may be an alternative approach at NO-induced increases in muscle blood flow that may provide an anabolic approach to exercise training,” said Dr. Willoughby.

Dr. Willoughby’s session at ISSN, “Expanding the Knowledge on Applications for L-Citrulline: Exercise Performance and Beyond”, will take place on Saturday, June 15, 2013 at 8 AM. 

About Kyowa Hakko USA
Kyowa Hakko USA is the North American sales office for Kyowa Hakko Bio Co. Ltd., an international health ingredients manufacturer and world leader in the development, manufacturing and marketing of pharmaceuticals, nutraceuticals and food products. Kyowa is the maker of branded ingredients including Cognizin® Citicoline, Lumistor® L-Hydroxyproline, Pantesin® Pantethine, Setria® Glutathione, as well as SustamineTM L-Alanyl-L-Glutamine. For more information visit

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