L-theanine Must be Pure for Proper Absorption, Study Finds

A new study finds that L-theanine must be administered in its pure form rather than as the mixture of D-theanine and L-theanine found in many nutritional supplements in order to be absorbed by the body.

Researchers from Iowa State University orally administered to rats pure L-theanine, pure D-theanine, and an ingredient commercially marketed as ?L-theanine? that actually was a racemic mixture (a 50:50 split between D- and L-theanine). They then measured blood concentrations, urinary excretion, and a marker of theanine metabolism in the blood.

The results show that the animals? bodies had a preference for pure L-theanine and that the pure form is better absorbed in the gut. The concentration of L-theanine seen in the blood was greater with the pure L-theanine than it was with the racemic mixture. There was also a trend toward greater urinary excretion of L-theanine when consumed as the racemic form.

The majority of clinical and animal studies determining the bioavailability of L-theanine have used Suntheanine, a form of pure L-theanine.

Simple HPLC analysis cannot discriminate between D- and L-theanine yet a number of companies are relying upon this method to assert that they have the pure L-isomer, declared Scott Smith, Vice President of Taiyo Kagaku, the manufacturer of Suntheanine in Minneapolis. The patented enzymatic synthesis method locks in the L-isomer and thus gives us pure L-theanine every batch. Suntheanine is an elegant example of where chemistry dictates biology.?

For the benefits of L-theanine and technical information click here

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Reference:
Desai MJ, Gill MS, Hsu WH, Armstrong DW. Pharmacokinetics of theanine enantiomers in rats. Chirality. 2005 Mar;17(3):154-62.

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