Benefits of L-Ornithine

Evidence-Based Benefits

• Ammonia detoxification — ornithine stimulates the urea cycle, accelerating ammonia-to-urea conversion and reducing blood ammonia levels during prolonged exercise (Sugino et al., 2008)
• Exercise fatigue — a 2014 RCT found ornithine supplementation reduced perceived fatigue and improved energy during prolonged cycling, correlated with reduced blood ammonia (Demura et al., Clinical Nutrition)
• Sleep quality — 400 mg ornithine before bed improved sleep quality and reduced morning cortisol in stressed Japanese workers (Miyake et al., 2014, Nutrition Journal, n=52)
• Hepatic encephalopathy — L-ornithine-L-aspartate (LOLA) is an established treatment for hepatic encephalopathy (Butterworth & McPhail, 2019, meta-analysis)
• Growth hormone release — ornithine at 12 g stimulated GH release in some studies, though the practical significance is debated (Bucci et al., 1990)

What the Research Says

L-Ornithine's role in the urea cycle is well-established biochemistry, but supplementation evidence is still emerging. The most robust clinical use is as LOLA for hepatic encephalopathy. For exercise and sleep, studies are promising but small. The sleep study showing improved quality with just 400 mg is notable for its low effective dose. More large-scale RCTs are needed to confirm exercise performance benefits.

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