Why citrulline beats arginine for making nitric oxide
Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Your body makes nitric oxide from arginine, but eating arginine pills doesn't work well because your liver breaks them down too fast. Citrulline pills go straight to the liver and get turned into arginine instead — so more nitric oxide gets made.
Surprising Findings
L-Arginine had zero measurable effect on plasma levels, nitrate, or cGMP — even at doses up to 1.6g twice daily.
For years, arginine was the go-to nitric oxide booster in sports and heart health supplements. This study shows it’s biologically ineffective in healthy people.
Practical Takeaways
Switch from L-arginine to L-citrulline supplements if you want to boost nitric oxide — take 3g twice daily.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Your body makes nitric oxide from arginine, but eating arginine pills doesn't work well because your liver breaks them down too fast. Citrulline pills go straight to the liver and get turned into arginine instead — so more nitric oxide gets made.
Surprising Findings
L-Arginine had zero measurable effect on plasma levels, nitrate, or cGMP — even at doses up to 1.6g twice daily.
For years, arginine was the go-to nitric oxide booster in sports and heart health supplements. This study shows it’s biologically ineffective in healthy people.
Practical Takeaways
Switch from L-arginine to L-citrulline supplements if you want to boost nitric oxide — take 3g twice daily.
Publication
Journal
British journal of clinical pharmacology
Year
2008
Authors
E. Schwedhelm, R. Maas, R. Freese, D. Jung, Z. Lukács, A. Jambrecina, W. Spickler, F. Schulze, R. Böger
Related Content
Claims (6)
Taking L-citrulline by mouth raises your blood levels of L-arginine better than taking L-arginine directly, because your body processes L-citrulline more efficiently and doesn’t break it down too early in the liver.
Taking L-citrulline or L-arginine supplements for a week didn’t make blood vessels relax better in healthy people, even though their bodies showed more of a chemical linked to blood vessel health. So, boosting that chemical briefly doesn’t seem to help blood flow in the short term.
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 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 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.