Tea Constituent Supports Slumber

Clinical study with Suntheanine® reveals superior sleep quality

Minneapolis – Researchers from the National Institute of Mental Health in Japan have found that taking a pure L-theanine dietary supplement (Suntheanine®) before bed produces a significant improvement in sleep quality. The results were released at the Society of Physiological Anthropology conference in Tokyo in late 2003 and will be presented at the 17th European Sleep Research Society (ESRS) Congress October 2004 in Prague.

The research team’s findings outline the first human study showing that L-theanine, an amino acid found in green tea, can enhance the quality of actual sleep experienced by young subjects.

“Our clinical study strongly suggests that Suntheanine supplementation of young men can improve both the quality of sleep and the mental state of being refreshed upon awakening,” offered Dr. Shuichiro Shirakawa, a professor at The National Center of Neurology and Psychiatry at NIMH in Tokyo. “These results add to previous human studies showing that Suntheanine supplementation can foster a relaxed state, which may improve one’s entry into, and maintenance of, sleep,” he added.

The Japanese research team first had 22 young men (12 daytime workers, average age of 28; 10 students, average age of 26) undergo 3-day acclimatization period. They then were asked to take 200 mg of Suntheanine or a placebo one hour before bedtime for six consecutive days. After subjects completed this first blinded supplementation phase they were then “crossed over” to receive the opposite treatment. Subjects’ sleep performance was assessed by interviews upon awakening, self-reported questionnaires, and a wrist actigraph, which records bodily movement during sleep.

The entire group reported a statistically significant absence of “feeling exhausted” and a reduced need for sleep during the Suntheanine administration period, relative to placebo. Seven of the ten collegiate males showed a statistically significant improvement in sleep efficiency, an index of actual sleep time enjoyed between the time of falling asleep and the final morning awakening. These subjects also reported a superior mental state prior to falling asleep and a decreased occurrence of nightmares during the Suntheanine phase but not during placebo. Notably, the total time from falling asleep to awakening was unchanged during both placebo and Suntheanine phases.

“We are quite encouraged by the results of this clinical trial with Suntheanine, which marry well with our previous findings of promoting a relaxed state as measured by brain alpha waves,” said Scott Smith, Vice President of Taiyo International’s offices in Minneapolis. “These findings augment the evidence base for our enzymatically produced L-theanine and further distance us from the numerous other ingredients that claim to be “L-theanine”. Research we supported at Dr. Daniel Armstrong’s laboratory at Iowa State University, published last month in Rapid Communications in Mass Spectrometry, underscores the chemical differences between Suntheanine and other theanine ingredients. Suntheanine is chemically unique and the only L-theanine with evidence of human safety and efficacy,” he concluded.


Taiyo International is the North American sales office for Taiyo Kagaku Japan, a leading manufacturer of functional ingredients for the food, beverage and dietary supplement industries. Taiyo focuses on the development of innovative ingredients, derived from natural sources, to further develop the body’s ability to protect and manage one’s health.

Suntheanine is Taiyo’s exclusive brand of pure L-theanine, supported by extensive clinical trials. Suntheanine is protected by over 40 U.S. and international patents for its various physiological efficacies and L-isomer-specific production processes.

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