Wrong form of theanine interferes with absorption

- Last updated on GMT

Related tags: Tea, Metabolism

D-theanine can inhibit the body's absorption of the amino
L-theanine and may present a health risk to consumers, suggest
researchers at Iowa University.

Found in green tea, L-theanine is believed to have relaxing, stress relieving properties, as well as the ability to improve mental acuity and improve sleep quality.

D-theanine is a different amino acid and its biological effects are unknown since no studies have been carried out, according to according to Dr Daniel Armstrong, who led the research team.

In a study published in Chiralty journal, Armstrong's team fed different theanine ingredients to three groups of rats. One received a commercially-available product claiming to be L-theanine but which actually also contained D-theanine, the second group received pure D-theanine and the third group pure L-theanine.

After measuring blood concentrations, urinary excretion and theanine metabolism in the blood, they noted that, although administered in equal amounts, more L-theanine was absorbed from the pure source than from the source which also contained D-theanine.

"What poses a potential concern to the consumer is the safety and efficacy of theanine racemates sold as L-theanine, as this is a complete unknown," said Armstrong.

The latest study builds on Armstrong's research in 2003 when, after analysing several commercially available raw materials claiming to be pure L-theanine, he found that most contained more than just the L-form.

The presence of D-theanine is difficult to detect, which means that some companies are able to pass off adulterated product as the real thing.

"Simple HPLC analysis cannot discriminate between D- and L-theanine," said Scott Smith, VP of Taiyo International, the maker of Suntheanine.

Taiyo claims Suntheanine may be the only pure source on the market, guaranteed as such since it produced using a patented enzymatic synthesis method that locks in the L-isomer.

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