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  Evaluated for:
Effectiveness Rating Effectiveness Rating
Blood Pressure Lowering
+1 (Slight Evidence)


  • Citrulline is an alpha-amino acid. The L- form of citrulline is naturally occurring, but is not essential for protein synthesis.
  • L-citrulline is obtained from both food and internal body sources in the intestines and liver. One rich source of L-citrulline is watermelon, which contains 0.7-3.6 mg per gram of fruit. Ingestion of 1-2 cups of watermelon juice three times daily provides 1-2 grams of L-citrulline.
  • L-citrulline is converted to L-arginine, which relaxes blood vessels (vasodilation) and reduces blood pressure via increased levels of nitrous oxide. By a related mechanism, L-citrulline may also provide an alternative to medications such as sildenafil (Viagra®) in treatment of mild-moderate erectile dysfunction.
  • One small study suggested that L-citrulline may be useful in adults with pre-hypertension. Mild blood pressure elevation is a documented risk factor for subsequent development of high blood pressure and heart disease. A study of watermelon extract supplementation showed improved arterial function in a small group of obese adults.


  • L-citruline-mediated vasodilation may lead to hypotension (low blood pressure) when taken with antihypertensives, nitrates, possibly erectile dysfunction medications, and certain prostate medications.
  • Few adverse effects are recorded for this product. Patients should be aware that while this may indicate relative safety, it may also be a reflection of the relatively small size and number of research studies conducted to date.

DOSAGE:In clinical trials, L-citrulline has been used safely for up to 9 months in doses up to 0.13 grams/kg/day, corresponding to 9 grams/day for a 70-kg person.

CONCLUSION:If you elect to try Citrulline, remember to include it in your list of medications when you visit your doctor and other health care providers.

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