Scientists from Unilever R&D have modelled the absorption and breakdown of L-theanine in humans, with results that may cast more light on the potential brain benefits of the tea compound.
The new research is said to be the first study to measure the pharmacokinetic parameters of L-theanine – assessing how the compound is absorbed and removed from blood plasma after dietary ingestion.
The results of the study, published in the Journal of Functional Foods, are believed to provide new model data, which could support further research into the potential health benefits of L-theanine.
“The obtained set of pharmacokinetic parameters from this study allows accurate prediction of L-theanine concentrations in plasma over a relevant dose range.
“The ability to predict L-theanine concentration may facilitate research about putative health effects of L-theanine in the brain,” stated the Unilever scientists.
“The impact of the composition of other food matrices like sugar, milk and … ingested meals … on the pharmacokinetic behaviour of L-theanine is unknown and could be studied in future research,” they added.
Tea leaves contain numerous compounds, including caffeine and flavonoids – that dissolve when the leaves are mixed with hot water.
The amino acid L-theanine (c-glutamylethylamide) is almost exclusively found in tea plants. The compound only exists in the free form, and is the principal free amino acid in tea - accounting for approximately 50 percent of the total free amino acids.
Various health effects have been associated with L-theanine, including relaxation, neuroprotective effects, and improved attention.
During rest, L-theanine increases alpha activity in EEG models - suggesting greater relaxation. Whilst the amino acid is known to induce changes in alpha activity that indicates increased attentional processing during tasks that require attention.
The authors note that the source of L-theanine, and the matrix in which it is administered, might have an impact on its pharmacokinetics and absorption rate, respectively.
The new Unilever research investigated the pharmacokinetics of L-theanine in humans, using pure L-theanine from an aqueous solution, L-theanine from black tea, and L-theanine from enriched black tea.
In all cases, the researchers reported that L-theanine was absorbed quickly, and resulted in maximum plasma concentrations of up to approximately 5 mg/L.
The results revealed that in aqueous solutions, such as water or tea, almost immediate release of L-theanine can be expected.
The researchers noted that dose-independent pharmacokinetic parameters were fairly consistent across the various doses, L-theanine source and matrices, whilst dose dose-dependent parameters were consistent - after correction to allow for body weight.
The authors concluded that L-Theanine - be it pure, biosynthetic, or tea-derived - is quickly absorbed and eliminated from the systemic circulation in humans.
Researchers stated that the pharmacokinetic model “will facilitate the design of studies related to L-theanine effects.”
Source: Journal of Functional Foods
Published online ahead of print, doi: 10.1016/j.jff.2010.08.001
“Human disposition of L-theanine in tea or aqueous solution”
Authors: P.C. van der Pijl, L. Chen, T.P.J. Mulder