University Study Shows Some Brands of 'L-Theanine' Can Be Imposters


AMES, Iowa, October 7, 2003 — L-theanine, an amino acid found in green tea and associated with relaxing effects, may sometimes have a different composition in bulk commercial products, researchers from Iowa State University announced today.

The findings of Dr. Daniel Armstrong, the Caldwell Professor of Chemistry at Iowa State University, are from a series of chemical analyses performed on several commercially available raw materials claiming to be pure L-theanine. Dr. Armstrong’s laboratory was the first to report on the chemical forms of L-theanine in brewed tea and tea leaves, published in the Journal of Agricultural and Food Chemistry in 2000.

“Our analysis of several ingredients being sold and marketed as “L-theanine” revealed that they indeed are not just the L-form,” said Armstrong. “We found all of those tested that are made through chemical synthesis or claiming to be extracted from green tea actually have about 50% present as D-theanine. The only material (tested) that proved to be pure L-theanine was the Suntheanine brand, produced via biofermentation, having greater than 99.95% L-theanine, our current detection limit.”

Armstrong said their method is very selective at separating out the D- and L-forms. “As amino acids go, in the body the D-form may have a very different action, like putting your left shoe on your right foot. There have been no studies on the biological effects of D-theanine or D-theanine-rich “L-theanine”, he added.

The purity of amino acids, which is related to their “stereochemistry”, can have a dramatic influence on their metabolism and biological activity. “Chemical synthesis of L-theanine, or its purported extraction from green tea, is fraught with the problem of forming much greater amounts of D-theanine than found in tea,” offered Scott Smith, Vice President of Taiyo International, Inc., based in Minneapolis, Minnesota. “Our proprietary biological fermentation process assures dietary supplement manufacturers, and consumers, that they are getting only pure L-theanine. We know the biological effects of our Suntheanine® brand L-theanine.” he concluded.

The study findings are being submitted for presentation at a national scientific research conference and for publication in a peer reviewed journal. The study was sponsored by Taiyo Kagaku Co., Ltd., Yokkaichi, Japan. (


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.

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