L-CitrullineThe amino acid before arginine.

Citrulline takes its name from Citrullus, the Latin name for watermelon. The body can convert it into L-Arginine, which is then used in the pathway that produces nitric oxide: a short-lived signalling molecule involved in normal blood-vessel relaxation.

Why citrulline, not only arginine?

Oral arginine is substantially handled by the gut and liver before it reaches the circulation. Citrulline follows a different route and can raise circulating arginine. That biochemical pathway is established; the size and practical meaning of any benefit still depend on dose, population and outcome measured.

What the evidence can—and cannot—say

Human studies have examined citrulline across exercise and vascular settings, often at doses higher than the 1,500 milligrams used in XUFU Original. Some trials report changes in nitric-oxide markers or measures of vascular function; results should not be stretched into a promise about an individual outcome.

XUFU Original combines 1,500 milligrams of L-Citrulline with 250 milligrams of L-Arginine per full four-capsule serving. We describe the pathway and the formulation, not a guaranteed effect.

Safety before mythology

If you take prescription medicine—especially nitrates, blood-pressure medicine, blood thinners or prescription erection tablets—speak to a GP or pharmacist before use. Do the same if you have a diagnosed cardiovascular condition. This page is general information, not medical advice.

Sources and further reading

1. A critical review of L-Citrulline, L-Arginine and vascular function, Nutrients, 2023.
2. Randomised trial examining L-Citrulline and nitric-oxide markers after exercise, British Journal of Nutrition, 2022.
3. Review of potential therapeutic uses and evidence limitations, Journal of Inherited Metabolic Disease, 2024.

Editorial review: 28 October 2026. We link to the research so readers can inspect the evidence and study doses directly.

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