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Japan researchers are the first to publish credible research showing moderate doses of the humble amino acid l-ornithine may help dampen stress levels and improve sleep quality1. In our fast-paced western world, less stress and better sleep are highly desirable for most individuals. Inspiration for the study came from initial findings on the response of rats to l-ornithine administration by the same authors2. After feeding orally on l-ornithine, rats were found to  have a lower stress response – prompting researchers to see if similar results could be produced in humans.

To test their hypothesis, the researchers gave a total of fifty-two otherwise healthy Japanese individuals either 400mg of l-ornithine just before bed or a matching placebo. Sleep quality was measured using a standardised and validated questionnaire (called the Athens Insomnia Scale) while stress levels were evaluated by means of dehydroepiandrosterone-sulphate (DHEA-S) and cortisol levels. The study was conducted over an 8-week period, which the authors deemed to be long-term compared with previous studies on l-ornithine which have lasted just a few weeks.

According to the sleep questionnaire, subjects experienced greater sleep quality and lower stress by virtue of lower serum cortisol levels and a decreased cortisol/DHEA-S ratio levels after taking the encapsulated l-ornithine compared with placebo. Studies way back in the early 1970’s3 and mid-80’s4 were the first to show that oral administration of ornithine could increase growth hormone release and possibly promote better sleep. So it’s good to see some up-to-date research which seems to validate these earlier findings.

Ornithine is traditionally known for the important role it plays in ammonia detoxification in the liver. As a toxic by-product of protein, ammonia levels can sometimes raise to dangerous levels in individuals consuming very high protein diets. In this sense, supplementing with ornithine is a beneficial strategy for anyone pushing the boundaries of protein intake. It’s important to note, however, that in order to see the growth hormone boosting and sleep benefits with ornithine supplementation, it’s important that it’s taken last thing at night before going to bed and preferably on an empty stomach.


1. Miyake et al. Randomised controlled trial of the effects of L-ornithine on stress markers and sleep quality in healthy workers. Nutrition Journal. 2014;13:53.
2. Kurata K, et al. Orally administered L-ornithine reduces restraint stress-induced activation of the hypothalamic-pituitary-adrenal axis in mice. Neurosci Lett. 2012;506:287–291.
3. Gourmelen M, et al. Effect of ornithine hydrochloride on growth hormone (HGH) plasma levels. Ann Endocrinol (Paris). 1972;33(5):526-8.
4. Krassowski J, The effect of ornithine alpha-ketoglutarate on growth hormone (GH) and prolactin (PRL) release in normal subjects. Endokrynol Pol. 1986;37(1):11-5.

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