L-Arginine is an amino acid critical to the production of nitric oxide (NO) in the body. NO helps regulate and improve blood circulation. L-Citrulline is a major precursor to L-Arginine and has been shown in other studies to increase L-Arginine levels, and thus improve NO production.
“We measured blood L- Arginine levels and Nitric Oxide levels 40 minutes and 60 minutes after amino acids administration. At both time points, the combination of L-Citrulline and L-Arginine had a better effect than the single amino acids,” said Ryusuke Nakagiri, senior director of strategic science at Kyowa Hakko USA.
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 (Cyclic guanosine monophosphate) concentrations, than with dosage with the single amino acids.