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

This study was a randomised, double-blind and placebo-controlled trial. Subjects were randomly allocated to either the L-ornithine group or placebo group.

Most previous studies have evaluated the short term effect of L-ornithine supplementation on healthy volunteers [26, 27]; we investigated the long term effect of L-ornithine supplementation on healthy volunteers. Eight weeks was chosen as the study period after consideration of the seasonal effect and the volunteer's burden.

Subjects ingested either L-ornithine or placebo capsules before going to bed every day for 8 weeks. Blood was collected four times during this clinical trial: before supplementation (0w), corresponding to the screening evaluation; 2 weeks (2w) and 4 weeks (4w) after taking the supplement; and at the end of the trial (8w).

We used the following three questionnaires to evaluate perceived stress, sleep quality and mood state: POMS [28], Athens Insomnia Scale (AIS) [29] and Ogri-Shirakawa-Azumi sleep inventory MA version (OSA-MA) [30]. The POMS questionnaire is a well established, factor-analytically derived measure of psychological distress, such as mood, for which high levels of reliability and validity have been documented. We used the short-form POMS, which consists of thirty adjectives rated on a 0–4 scale that can be consolidated into six mood scales: “tension-anxiety”, “depression-dejection”, “anger-hostility”, “vigor”, “fatigue” and “confusion”. The T score of the POMS questionnaire was calculated using the standard method [28], showing that higher T scores represent high levels of distress, with the exception of “vigor”. This questionnaire was completed by each study participant at 0, 2, 4, 6 and 8 weeks.

The AIS is a useful tool to assess the existence of insomnia. This self-administered psychometric instrument consists of eight items: difficulty with sleep induction, awakening during the night, early morning awakening, total sleep time, overall quality of sleep, problems with sense of well-being, and functioning, and sleepiness during the day. Each item was rated on a scale of 0 to 3, with 0 corresponding to “no problem at all” and 3 indicating “a very serious problem”. Thus, the total AIS score ranges from 0 (denoting absence of any sleep-related problem) to 24 (representing the most severe degree of insomnia). Volunteers completed this questionnaire at 0, 4, and 8 weeks.

The OSA sleep inventory is popularly used for evaluation of sleep quality in Japan. The MA version is more useful for middle-aged and old-aged people and consists of sixteen adjectives with responses rated on a 0–4 scale that can be consolidated into five factors: “sleepiness on rising”, “initiation and maintenance of sleep”, “frequent dreaming”, “refreshing” and “sleep length”. The OSA-MA score was calculated using an MS-Excel sheet [30], with higher scores indicating a good quality of sleep: this questionnaire was completed weekly for 8 weeks.

The present study was conducted according to the guidelines laid down in the Declaration of Helsinki and all procedures involving human subjects were approved by the local ethics committee of Medical Corporation, Akihabara Medical Clinic. Written informed consent was obtained from all participants.

Fifty-two apparently healthy Japanese individuals participated in this study. The volunteers ranged in age from 30 to 60 years (male: female ratio, 2:3), and had full-time jobs, excluding those who engaged in shift work or physical work, such as carpenter or delivery person, and irregular work schedules. Subjects were selected based on their POMS questionnaire score, which should be above 50 in T scores of “fatigue” and below 50 in T scores of “vigor”.

Smokers, pregnant or lactating women, or persons who habitually took L-ornithine, medication or supplements to improve stress, fatigue or sleep were excluded from this study. Also excluded were those with a past history of diabetes, hepatic disease, renal disease, hypertension, ischemic heart disease or abnormal glucose tolerance.

L-Ornithine monohydrochloride and microcrystalline cellulose (FD-301) were purchased from Kyowa Hakko Bio (Tokyo, Japan) and Asahi Kasei Chemicals (Tokyo, Japan), respectively. Two kinds of small hard capsules were prepared, with one type of capsule containing 500 mg of L-ornithine monohydrochloride (400 mg L-ornithine) and 160 mg of microcrystalline cellulose per 2 capsules and the other (placebo) containing 560 mg of microcrystalline cellulose per 2 capsules.

Participants were instructed not to eat breakfast after 8:00 am and abstain from smoking and caffeinated drinks prior to blood sampling. Blood samples were collected by venipuncture from all participants between 11:00 and 13:00. Serum cortisol and DHEAS levels were analyzed by commercial laboratories (BML Inc., Tokyo, Japan).

Values are presented as the mean ± standard error (SEM). Two-way analysis of variance was used to evaluate the significance of differences between the placebo and L-ornithine groups followed by pairwise comparisons and unpaired t tests. P values less than 0.05 were considered to be statistically significant.

There were no statistical differences between the two groups at baseline (Table 1). During the 8 study weeks of the study, no adverse events were observed.

Most of the study subjects were general office workers with 24 out of 26 participants in the placebo group, and 23 out of 26 participants in the L-ornithine group.

Changes in POMS scores are shown in Figure 1. There was a trend toward an improved mood indicated by each score compared to 0 weeks but there was no significant difference between the two groups. There was a significant improvement in self-reported “anger-hostility” at 2 weeks and 6 weeks in the L-ornithine group compared to the placebo group (Figure 1C).

As shown in Figure 2, the AIS score revealed a trend towards improved insomnia in both groups from 0 weeks to 8 weeks. Furthermore, the AIS score indicated significant improvement in the L-ornithine group at 4 weeks in comparison with the placebo group.Scores for the OSA-MA for each group over an 8-week period are shown in Figure 3. Scores of three OSA-MA items, “sleepiness on rising” (Figure 3A), “initiation and maintenance of sleep” (Figure 3B) and “refreshing” (Figure 3D), tended towards improved sleep quality in both groups without significant between-group differences. Scores for “frequent dreaming” (Figure 3C) and “sleep length” (Figure 3E) were unchanged in the placebo group, however, the score for the L-ornithine group significantly improved for self-reported “initiation and maintenance of sleep” (Figure 3B) at 4 weeks and “sleep length” (Figure 3E) at 5 to 7 weeks in comparison with the placebo group.

While the concentration of serum DHEA-S was not increased by L-ornithine intake, serum cortisol concentration decreased in the L-ornithine group. Although the change in either level did not differ significantly between the two groups at any examination point (Figure 4A, 4B), the change in cortisol/DHEA-S ratio significantly decreased in the L-ornithine group after 4 weeks (Figure 4C). The cortisol/DHEA-S (×100) ratio was calculated based on serum cortisol and DHEA-S concentrations.