Figure 1. Chemical structure of L-theanine, glutamic acid and glutamate.
| Journal of Food Bioactives, ISSN 2637-8752 print, 2637-8779 online |
| Journal website www.isnff-jfb.com |
Review
Volume 13, March 2021, pages 32-39
Theanine as a promising agent for health-promotion: a review
Figure
Table
| Functions | Study design | Outcomes | Reference |
|---|---|---|---|
| Relieving stress and anxiety | L-theanine (25–50 mg twice daily) for the anxious dogs | Effective for treating anxiety-related behaviors without causing any side effects | Araujo et al. (2010) |
| L-theanine (2 and 4 mg/kg) for the stressed mice | Ameliorated chronic stress-induced disorders | Tian et al. (2013) | |
| 4-week L-theanine intake (200 mg/day) on healthy adults | Ameliorated stress-related ailments and cognitive impairments | Hidese et. al., 2019) | |
| Oral administration of L-theanine (200 mg) on the students | Increased α-brain wave activity in the occipital and parietal regions of the brains | Kobayashi et al. (1998) | |
| Oral intake of 200 mg L-theanine on the healthy participants with induced high-stress | Attenuated the rise in heart rate, salivary immunoglobulin A responses and blood pressure | Kimura et al. (2007); Yoto et al. (2012) | |
| Improving sleep quality | Low (22.5 and 37.5 mg/kg) and high (75 and 150 mg/kg) doses of L-theanine administration on the rats | Low dose attenuated the caffeine-induced sleep disturbances, while high dose exhibited the opposite effect | Jang et al. (2012) |
| 4-week administration of L-theanine (200 mg daily) on healthy adults | Improved sleep quality via reducing sleep latency, sleep disturbance, and use of sleep medication | Hidese et al. (2019) | |
| 6-week administration of L-theanine (400 mg daily) on the boys with ADHD | Improved sleep percentage and sleep efficiency scores, along with a non-significant trend for less activity during sleep | Lyon et al. (2011) | |
| Alleviating depression | 10-day L-theanine administration (1, 4 and 20 mg/kg) on the depressed mice | Reduced the immobility time in both the forced swim test and tail suspension test | Yin et al. (2011) |
| 21-day L-theanine administration (2 mg/kg) on the rats with depression | Ameliorate behavioral disorders and increased circulating monoamine neurotransmitters | Shen et al. (2019) | |
| 8-week L-theanine administration (250 mg daily) on the patients with major depressive disorder | Exerted multiple beneficial effects on depressive symptoms, as well as anxiety, sleep disorder and cognitive impairments | Hidese et al. (2017) | |
| Enhancing learning ability and memory | 4-month L-theanine administration (180 mg daily) on the rats | Showed improved learning ability and memory | Juneja et al. (1999) |
| 6-week L-theanine administration (4 mg/kg daily) on young rats | Facilitated neurogenesis in the developing hippocampus, and thus improve recognition memory | Takeda et al. (2011) | |
| There doses (100, 200 and 400 mg) of L-theanine and a placebo were consumed by 27 healthy young adults | Improved attention in a dose-dependent manner | Dassanayake et al. (2020) | |
| The combination (200 mg L-theanine and 160 mg caffeine) was consumed by healthy participants | L-theanine and caffeine could exert a synergistic effect to decrease fMRI responses to distractor stimuli | Kahathuduwa et al. (2018) | |
| Decreasing the risks of neurodegenerative diseases | Oral administration of L-theanine (200 mg/kg) by the rats with induced oxidative damage in the brain | Increased the status of antioxidants, and the activities of creatine kinase, AchE, and ATPases | Sumathi et al. (2016) |
| L-theanine (25–50 mg/kg) intake by the rats with induced striatal toxicity | Decreased proinflammatory cytokines levels and restored striatal GABA, glutamate and catecholamine levels | Jamwal and Kumar (2017) | |
| 8-week injection of L-theanine (100 or 200 mg/kg/day) in the mice with Cadmium (Cd)-induced brain injury | Reduced Cd level in the brain and plasma, and inhibited Cd-induced neuronal cell death | Ben et al. (2016) |