Are Tea Antioxidants Absorbed By The Body?

By Phillip Hogan

February 10th, 2010
Posted in Health

A recent study in the Journal of Nutrition into the bioavailability and catabolism of green tea flavan-3-ols in humans was carried out by a team of Italian researchers. The study is the latest, and perhaps most convincing, in a long line of scientific investigations into the relationship between tea, specifically green tea, and antioxidant absorption in the human body.

The aim of the study was to investigate green tea flavan-3-ols, also known as flavanols, absorption in the human body; or perhaps more precisely what percentage of the antioxidants contained within green tea stay in the body after digestion.

By measuring the catabolism, plasma pharmacokinetics and urinary excretion using high performance liquid chromatography with tandem mass spectrometry, the researchers hoped to discover the absolute bioavailability of flavan-3-ols – taking into account interaction with the gastrointestinal tract and its host microflora.

Twenty healthy human volunteers were examined and then were asked to ingested 400 mL of a ready-to-drink (RTD) green tea containing approximately 400 μmol of flavan-3-ols. The RTD contained tea leaves from Sri Lankan, lemon juice, sugar, dextrose, ascorbic acid and flavouring.

Urine and plasma samples were then collected four and twenty-four hours after initial ingestion of the RTD and measurements and analysis was undertaken.

Thirty-nine relevant catabolites were identified in the biological fluids by tandem mass spectrometry.

Results showed a calculated bioavailability equal to 39 percent within the studied participants (almost a 40 percent absorption of antioxidants), with varying urinary excretion of colonic metabolites – believed to be related to individual differences in colonic microflora. Epigallocatechin-3-galate, which is the most commonly found catechin in tea, was the only un-metabolized compound as well as the highest in absolute concentration.

The study concluded by stating that its results not only demonstrated that green tea catechins are more bioavailable than previously thought, but also that regular consumption of RTD green tea containing flavan-3-ols allows a ‘non-marginal exposure of the human body to these catabolites, somehow justifying the numerous beneficial actions described as linked to green tea intake’.  

References:

Del Rio D, Calani L, Cordero C, Salvatore S, Pellegrini N, Brighenti F. Bioavailability and catabolism of green tea flavan-3-ols in humans.
Nutrition. 2010 Jan 14. [Epub ahead of print]

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Contact Phillip Hogan at phil@allabouttea.co.uk

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