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.

In healthy adult volunteers, participants receive either 3 g L-citrulline twice daily or placebo for 7 days in two randomized, separated treatment periods with a washout interval; urinary nitrate and cGMP are measured before and after each period to quantify the 36% and 32% increases stated in the claim.

Healthy adults are randomly assigned to either L-citrulline (3g BID) or placebo for 7 days; urinary nitrate and cGMP are measured at baseline and day 7 to determine if the supplement group shows a statistically significant 36% and 32% increase compared to placebo.

Healthy adults take 3 g L-citrulline twice daily for 7 days, and urinary nitrate and cGMP are measured before and after to assess whether the reported 36% and 32% increases occur without a control group.

Healthy adults self-administer L-citrulline at 3g BID for 7 days and report urinary biomarker changes via home collection kits, with lab analysis to confirm the 36% and 32% increases.

Animal models or cell cultures exposed to L-citrulline at equivalent human doses to assess nitric oxide pathway activation and downstream cGMP/nitrate production as a proxy for human effects.