Nitric Oxide — Frequently Asked Questions
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Frequently Asked Questions
Why is L-citrulline better than L-arginine for nitric oxide?
Why is L-citrulline better than L-arginine for nitric oxide?
L-arginine is the direct precursor to nitric oxide, but when taken orally, 40-60% is broken down by the enzyme arginase in the liver before reaching systemic circulation. L-citrulline bypasses this first-pass metabolism entirely. Once in the bloodstream, the kidneys convert citrulline to arginine, which is then used for NO production. A 2008 study by Schwedhelm et al. showed that oral citrulline raised plasma arginine levels more effectively than an equivalent dose of arginine itself.
Can I combine L-citrulline with beetroot for more nitric oxide?
Can I combine L-citrulline with beetroot for more nitric oxide?
Yes, and this is actually a smart approach. L-citrulline and beetroot increase NO through entirely different biochemical pathways: citrulline feeds the NOS enzyme pathway (arginine to NO), while dietary nitrate uses the nitrate-nitrite-NO pathway mediated by oral bacteria. Combining both provides multi-pathway NO support and may produce synergistic effects on blood flow and exercise performance.
Do nitric oxide supplements help with muscle pumps?
Do nitric oxide supplements help with muscle pumps?
Yes. The "pump" during exercise is caused by increased blood flow and fluid accumulation in working muscles — exactly what nitric oxide promotes. L-citrulline at 6-8g pre-workout reliably enhances the pump sensation by dilating blood vessels feeding skeletal muscle. While the pump itself is temporary, the improved nutrient and oxygen delivery during training may contribute to better long-term training adaptations.
References
- Schwedhelm E, Maas R, Freese R, Jung D, Lukacs Z, Jambrecina A, Spickler W, Schulze F, Boger RH (2008). Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. British Journal of Clinical Pharmacology. DOI PubMed
- Trexler ET, Persky AM, Ryan ED, Schwartz TA, Stoner L, Smith-Ryan AE (2019). Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis. Sports Medicine. DOI PubMed
- Siervo M, Lara J, Ogbonmwan I, Mathers JC (2013). Inorganic nitrate and beetroot juice supplementation reduces blood pressure in adults: a systematic review and meta-analysis. Journal of Nutrition. DOI PubMed
- Cormio L, De Siati M, Lorusso F, Selvaggio O, Mirabella L, Sanguedolce F, Carrieri G (2011). Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology. DOI PubMed