A study recently published by the American College of Sports Medicine shows oral supplementation with L-citrulline before exercise may help reduce gastrointestinal (GI) problems associated with physical strain during strenuous exercise.
Participants in the double-blind, placebo-controlled study took 10 grams of L-citrulline orally before exercise. Subsequent tests showed increased levels of L-arginine, an amino acid critical to production of nitric oxide (NO). Blood flow in the stomach and small intestine drop during exercise, which can lead to damage to fragile linings and blood vessels and may be responsible for unpleasant GI symptoms. Nitric oxide is known to supports blood circulation, especially in the presence of L-arginine.
“The results of this study may be useful for athletes with ischemia-related abdominal symptoms during strenuous exercise,” said researcher Dr Kaatje Lenaerts of 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.”
According to Kyowa Hakko, L-citrulline is a better precursor of arginine and NO than arginine itself. This is shown by acute oral administration of L-citrulline raising plasma arginine levels to about 227 percent with 3.8 grams/body surface area of L-citrulline (within 4 hours) compared to only 90 percent with the equivalent dose of arginine.
And a related animal study published in November in Biochemical and Biophysical Research Communications showed L-citrulline plus L-arginine supplementation caused a more rapid increase in plasma L-arginine levels and marked enhancement of NO bioavailability, including plasma cGMP concentrations, than with dosage with the single amino acids. Blood flow in the central ear artery in rabbits was also significantly increased by L-citrulline plus L-arginine administration as compared with the control.
Kyowa Hakko Bio Co. Ltd. provided the L-citrulline used in the study.