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.

In healthy adults with elevated ADMA (confirmed by baseline plasma measurement), participants receive L-citrulline (3 g twice daily) and L-arginine (matched dose) in randomized order with a 7-day washout between arms. Plasma L-arginine AUC and Cmin are measured via serial blood sampling over 24 hours after each intervention. Nitric oxide metabolites (nitrite/nitrate) are also measured as a downstream marker. Duration: 2 weeks per arm, total 4 weeks per participant.

Two groups of healthy adults with elevated ADMA are assigned to either L-citrulline (3 g twice daily) or L-arginine (3 g twice daily) for 7 days. Plasma L-arginine is measured at baseline and day 7 at multiple time points to calculate AUC and Cmin. Nitric oxide metabolites are assessed as a functional outcome. All participants maintain standardized diet and activity.

Healthy adults with elevated ADMA receive L-citrulline (3 g twice daily) for 7 days. Plasma L-arginine is measured at baseline and on day 7 at multiple time points to determine AUC and Cmin. The magnitude of increase is compared to published historical data for L-arginine in similar populations.

Human liver or endothelial cell lysates are exposed to L-citrulline or L-arginine at physiological concentrations. The rate of conversion to nitric oxide precursors and inhibition by ADMA is measured to assess whether L-citrulline bypasses ADMA-mediated inhibition more effectively.

A small group of healthy adults with elevated ADMA self-report or are monitored taking L-citrulline (3 g twice daily) for 7 days. Plasma L-arginine levels are measured before and after, and changes in AUC and Cmin are recorded without randomization or blinding.