400-mg capsule of L-ornithine improves sleep

If, every evening before going to sleep, you take a capsule containing 400 mg L-ornithine, the quality of your sleep will gradually improve. You’ll fall asleep faster, sleep more deeply and for longer, and you’ll feel better during the day, write researchers at the Japanese Kirin Company in Nutrition Journal.

Kirin is looking for applications for ornithine. This search has been prompted by animal studies in which orally administered L-ornithine had an anxiety reducing effect on mice subjected to stressful situations as a result of its activity in the brain. [Nutr Neurosci. 2011 Nov;14(6):243-8.] What exactly L-ornithine does there is not known. What is known is that it does not inhibit the synthesis of neurotransmitters such as dopamine. [Neurosci Lett. 2012 Jan 11;506(2):287-91.] L-Ornithine supplementation does inhibit the synthesis of the stress hormone cortisol in stressful situations.

In this study the researchers gave two dozen healthy subjects aged 30-60, who had complained in the past of mild work stress and moderate fatigue, a capsule containing 500 mg L-ornithine HCl every day for eight weeks. The amount of L-ornithine in each capsule was 400 mg. The subjects took the capsule before going to bed. A control group took a placebo.

The L-ornithine supplementation [black circles] lowered the cortisol level a little, but had no effect on DHEA synthesis. The cortisol:DHEA ratio improved significantly as a result of supplementation.


During the daytime the subjects in the ornithine group felt less hostile and angry. [#1]


The subjects that took ornithine fell asleep faster and slept more deeply. They scored these aspects of their sleep higher than the subjects in the placebo group did. [#2] In addition, the subjects in the ornithine group slept for longer. [#3]

“Our study suggested that L-ornithine has a positive effect on stress and sleep in healthy workers”, the Japanese wrote. “L-ornithine might be beneficial for people who live a stressful life.”

Randomised controlled trial of the effects of L-ornithine on stress markers and sleep quality in healthy workers.


L-ornithine is a non-essential, non-protein amino acid. Although L-ornithine is contained in various foods, the amount is usually small.Recently, studies have shown that orally administered L-ornithine reduced the stress response in animals.From these findings, we speculated that L-ornithine may play a role in the relieve of stress and improve sleep and fatigue symptoms in humans. Through a randomised, double-blind, placebo-controlled clinical study, we asked if L-ornithine could be beneficial to stress and sleep in healthy workers.

Fifty-two apparently healthy Japanese adults who had previously felt slight stress as well as fatigue were recruited to be study participants and were randomly divided into either the L-ornithine (400 mg/day) or placebo group. They orally consumed the respective test substance every day for 8 weeks. Serum was collected for the assessment of cortisol and dehydroepiandrosterone-sulphate (DHEA-S). Perceived mood and quality of sleep were measured by the Profile of Mood States (POMS), Athens Insomnia Scale (AIS), and Ogri-Shirakawa-Azumi sleep inventory MA version (OSA-MA).

Serum cortisol levels and the cortisol/DHEA-S ratio were significantly decreased in the L-ornithine group in comparison with the placebo group. Also, anger was reduced and perceived sleep quality was improved in the L-ornithine group.

L-ornithine supplementation has the potential to relieve stress and improve sleep quality related to fatigue, both objectively and subjectively.

PMID: 24889392 PMCID: PMC4055948 DOI: 10.1186/1475-2891-13-53 [PubMed – indexed for MEDLINE]

Source: http://www.ncbi.nlm.nih.gov/pubmed/24889392