by Heidi Kyser

A team of researchers in Itlay has provided what it describes as the clearest evidence yet that antioxidants in green tea are absorbed by the human body after consumption.

Researchers from the Universities of Parma and Torina, and from the Research and Development Center in Alba, all in Italy, conducted the study, titled "Bioavailability and catabolism of green tea flavan-3-ols in humans." The results are published in the current edition of the medical journal Nutrition (click here for an abstract).

The team set out to determine the "absolute bioavailability" of green tea flavan-3-ols(sometimes referred to as flavanols, and including catechins); in other words, what percentage of the antioxidants in green tea stay in the body after being ingested. As the researchers noted in their report, previous studies have sought to answer this question; however, their results were limited by small sample groups, the inability to account for the activities of microflora in the intestines, and/or insufficient technology for measuring compounds that are either absorbed by the body or pass through it.

In this case, the team used a very high-tech method of analysis: high-performance liquid chromatography with tandem mass spectrometry on the urine and plasma of human subjects. Twenty volunteers, all healthy, took 400 milliliters of RTD green tea. Soremartec Italia of Alba, Italy, supplied the tea, which was brewed from tea leaves grown in Sri Lanka. According to Furio Brighenti, professor in the department of public health at the University of Parma, and one of the lead researchers in the study, the RTD consisted of an infusion of the leaves, plus sugar, dextrose, lemon juice, ascorbic acid and flavoring.

After four and 24 hours, the researchers collected fluid samples from the volunteers and performed the measurements. They discovered that epigallocatechin-3-gallate (commonly called EGCG) was the only un-metabolized compound and the highest in absolute concentration, compared with the other flavan-3-ols measured. Overall, "on average (in 20 healthy volunteers) and with all the possible errors due to analytical constraints, almost 40 percent of green tea flavan-3-ols were absorbed by the human body," said Brighenti.

He summarized the significance of the findings as follows: "To justify the benefits associated to the consumption of green tea, the ability of the human body to absorb its peculiar polyphenolic fraction should be demonstrated. With this study, we have shown that these molecules are efficiently absorbed in healthy volunteers and that they remain within the body for more than 24 hours after tea intake."