Taking a specific amino acid supplement called L-citrulline twice a day for a week helps the body make more nitric oxide, which shows up as higher levels of certain waste products in the urine — this suggests the body’s blood vessels might be working better.

Taking a specific amino acid supplement called L-citrulline twice a day for a week helps your body make more nitric oxide, which shows up as higher levels of certain chemicals in your urine.

Taking a specific amino acid supplement called L-citrulline twice a day for a week can help improve a key balance in your blood that lets your body make more nitric oxide — a molecule that helps your blood vessels relax and work better.

Taking a specific amino acid supplement called L-citrulline twice a day for a week helps healthy people with high levels of a certain compound in their blood to produce more of a helpful molecule that improves blood flow.

Taking a specific amino acid called L-citrulline twice a day for a week boosts a related chemical in your blood more than taking that chemical directly, which might help your body make more of a molecule that relaxes your blood vessels.

Taking a specific amino acid called L-citrulline twice a day for a week helps raise levels of another amino acid, L-arginine, in the blood more than taking L-arginine directly—this might help your body make more nitric oxide, which is good for blood flow.