The amino acid L-citrulline – which Kyowa Hakko manufactures in the US in Cape Girardeau, MO using a proprietary fermentation process – is said to play an important role in nitric oxide (NO) metabolism and regulation. L-Citrulline is converted to L-Arginine in the body to support L-Arginine and NO levels. Increased production of NO promotes vascular dilation which improves oxygen and blood circulation throughout the body.
Blood flow in the stomach and small intestine is known to drop during exercise, said the researchers, and this can lead to damage to fragile linings and blood vessels and may be responsible for unpleasant GI symptoms.
Researchers from Maastricht University Medical Centre in The Netherlands report that a single pre-exercise dose of L-citrulline is able to preserve blood flow to the intestine (splanchnic perfusion) and reduce intestinal injury during exercise.
“The mechanism probably entails increased arginine availability for NO-mediated vasodilatation. These data suggest oral L-citrulline supplementation to be a promising strategy to improve GI blood flow and prevent intestinal injury in athletes without adverse GI effects as observed for arginine,” wrote the researchers in the journal Medicine & Science in Sports & Exercise.
The Maastricht-based scientists recruited 10 men to participate in their double-blind, placebo-controlled study. Participants were given placebo or 10 grams of L-citrulline orally before exercise (cycling for 60 min at 70% of their maximum workload).
Results showed that plasma levels of arginine and citrulline increased as a result of L-citrulline ingestion, compared with that in placebo.
“Splanchnic hypoperfusion was prevented during exercise after L-citrulline ingestion,” they wrote, “whereas [splanchnic hypoperfusion] increased with placebo treatment.”
“The results of this study may be useful for athletes with ischemia-related abdominal symptoms during strenuous exercise,” said researcher Dr Kaatje Lenaerts from Maastricht University Medical Centre.
“The current study demonstrates that a single oral dose of L-Citrulline before exercise reduces intestinal injury and can be taken without side effects.”
The ingredient is preservative-free, allergen-free, and contains no artificial flavors or colors, said Kyowa.
L-Citrulline will be marketed by Kyowa Hakko USA as a food ingredient in the United States for use at levels of 275 mg of L-Citrulline/serving up to a maximum of 2000mg/day in various food products, such as beverages and beverages bases; grain products and pastas; and milk products.
Karen Todd, Senior Director Global Brand Marketing for Kyowa Hakko USA, told us that, to date, the L-citrulline business is currently in 80% sports nutrition and 20% cardiovascular health, with about 80% in supplements.
"We are looking to grow the food/beverage area," said Todd. "This ingredient was limited because of the Tawnsaura patents blocking the market, but the courts have ruled that their patent are void on Dec 14th. I think 2015 will be a nice year!"
Source: Medicine & Science in Sports & Exercise
Volume 46, Issue 11, Pages 2039-2046, doi: 10.1249/MSS.0000000000000332
“L-Citrulline Improves Splanchnic Perfusion and Reduces Gut Injury during Exercise”
Authors: K. van Wijck, K.A.P. Wijnands, D.M. Meesters, et al.