L-Theanine Impostors Abound: Peer-Reviewed Publication Declares Suntheanine® Genuine Article

Minneapolis - Researchers from Iowa State University analyzing a number of dietary supplement ingredients claiming to be L-theanine report that only Suntheanine® contains pure L-theanine. The results were published in the February 15 issue of Rapid Communications in Mass Spectrometry.

The study reports that all of the other commercially available materials claiming to be Ltheanine were actually nearly equal mixtures of D- and L-theanine, also known as racemic mixtures or racemates. L-theanine, an amino acid found in various teas derived from Camellia sinensis, has been shown in previous clinical studies to improve sleep quality and foster mental calmness.

“Our analyses reveal that several theanine ingredients marketed for use in dietary supplements are not what they claim to be,” offered Dr. Daniel Armstrong, Caldwell Distinguished Professor of Chemistry at Iowa State University. “Theanine extracted from tea is present in predominantly the L- form. Five of the six theanine ingredients we tested were racemates, suggesting they were chemically synthesized. Only Suntheanine, which is produced via an enzymatic process, appeared to be essentially pure L-theanine,” he added. The six samples of theanine were procured directly from their respective suppliers. The method employed by Dr. Armstrong and his graduate student Meera Desai was a refinement of a previous method developed in theanine isomer analyses of various tea products. The current method is able to resolve both D- and L-theanine isomers with even greater sensitivity and specificity.

Because virtually all of the animal and clinical research performed with theanine has used Suntheanine, a question arises whether theanine racemates would exhibit the same safety and efficacy. Studies with a variety of drugs have shown racemates to be inferior and/or less safe than single isomer forms. “It is quite possible that the pharmacological effects of L-theanine may be significantly different relative to a theanine ingredient containing appreciable quantities of D-theanine,” added Dr. Armstrong.

“We are reinforced by the findings of Dr. Armstrong’s lab. We have invested significant capital in the enzymatic production process, safety and efficacy studies, and intellectual property on Suntheanine,” said Scott Smith, Vice President of Taiyo International’s offices in Minneapolis. “These results add to the distinction of Suntheanine and its evidence base. Suntheanine is not simply a generic ingredient with a trademark. We believe it is the only clinical research-proven, pure L-theanine commercially available. We now have even more science to support this assertion,” he concluded.

The study was conceived and orchestrated by IMAGINutrition (Laguna Niguel, CA), on behalf of Taiyo. The research conducted by Dr. Armstrong’s laboratory in the Department of Chemistry at Iowa State University was supported by a grant from Taiyo. Dr. Armstrong has no other relationship or possible conflicts of interest involving Taiyo.


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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