Tea Intervention Trial in Smokers (1998-2002)

We have recently completed a Phase II randomized, controlled, dietary intervention study among smokers to study the effect of high consumption (4 cups per day) of decaffeinated green and black tea on oxidative DNA damage as measured by urinary levels of 8-OHdG, 8-epi-PGF2, MDA and tyrosines and 8-OHdG in white blood cells. The main aim of the study was to compare high consumers of green or black tea to the control group for change of oxidative DNA lipid and protein damage in urine and white blood cell. Adherence data show that consumption of 4 cups of tea per day is a feasible and safe approach.

Figure 1 shows that subjects on either green or black tea (n=142) are able to maintain high tea intake over the 4-month intervention and at 1 month later (follow-up).

Figure 1: Tea consumption (cups/month)

We also determined the systemic availability of tea polyphenols after 4 months of green and black tea consumption in urine and plasma samples using high performance liquid chromatography with the coulometric electrode array detection system. Figure 2 and Figure 3 illustrate the high levels of urinary and plasma catechins with consumption of decaffeinated green tea.

Our data showed a significant decrease in the urinary levels of 8-OHdG among the green tea group (Figure 4).