A new study in the journal Chirality suggests that dietary supplements that do not use pure L-theanine may not deliver the expected benefits. Researchers from an Iowa State University (ISU) study compared the pharmacokinetics of L-theanine, D-theanine, and an ingredient commercially marketed as "L-theanine' that actually was a racemic mixture of theanine (a 50:50 D- and L-theanine mixture, also known as a racemate).

The research team orally supplemented rats with three different theanine ingredients: a commercially available "L-theanine" that actually was a racemate, pure D-theanine and pure L-theanine. They then followed blood concentrations, urinary excretion and a marker of theanine metabolism in the blood.

"Our results quite convincingly demonstrate that, at least in animals, their metabolism preferentially selects L-theanine, beginning with absorption in the gut," stated Dr. Daniel Armstrong, from ISU's Department of Chemistry and the director of the research team in this investigation. When equal amounts of L-theanine were administered, coming from pure L-theanine or the racemate, the concentration seen in the blood was greater with the pure L-theanine.

Virtually all of the clinical studies and the majority of the animal studies that have been performed assessing the bioactivity of theanine have used Taiyo's Suntheanine. Taiyo International, Scott Smith, 763-398-3003, scott@taiyoint.com, www.taiyointernational.com