Much is known about the antioxidant properties of the catechins that are found in tea. However, for catechins to have any health benefits they must be available for use in the human body. To further understand how the tea catechins EGC, EGCG, ECG and EC are metabolised by the body much work has been carried out in research institutes. The uptake and health benefits of tea consumption depend on two main factor, firstly the total consumption of the catechins and secondary the bioavailiability of catechins in the body.

The concentrations of catechins following consumption has been measured in numerous body parts. Upon consumption the presence of the four main types of catechins that are found in green tea (EGC, EGCG, ECG and EC) have been recorded in the portal vein, this indicates that these tea catechins are absorbed by the body through the intestines.

Catechin Levels in the Plasma

Although the total amounts of EGCG in tea given to rats was higher than that of EGC and EC, the concentrations of EGCG in the plasma was much lower. Interestingly in mice the opposite occurred with there being a higher concentration of EGCG the plasma. In humans EGCG is found at about 2.5 fold less than that of ECG and 4-fold less than that of EGC.

It is interesting that following consumption of catechins in humans that the levels of EGCG and EGC in the plasma soon returned to normal, whereas those of ECG remained higher for 24 hours. This suggests that either the EGCG and EGC catechins are either not took up by the plasma, or more likely (especially given that catechins are rapidly metabolised) that once took up by the body catechins are rapidly used by the body.

Tea Catechin Bioavailiability in Other Parts of the Body

In addition to the intestines and plasma catechins have been found at significant levels in other parts of the body following their consumption.

1. EGC and EC: high levels in the kidney, bladder, esophagus, large intestine and prostate: lower levels in the heart, liver, spleen and thyroid.
2. EGCG: highest levels in large intestine and esophagus. Lower levels in other organs.

References
Cabrera et al (2006). Beneficial effects of green tea - a review. J. Am. Coll. Nutr. 25: 79 to 99
Higdon and Frei (2003). Tea catechins and polyphenols: health effects, , and antioxidant functions. Critical Reviews in Food Science and Nutrition 43: 89to .
Khan and Mukhtar (2007) Tea polyphenols for health promotion. Life Sciences 81: 519 to 533
Kim et al (2000) Plasma and tissue levels of tea catechins in and mice during chronic consumption of green tea polyphenols. and Cancer 37: 41 to 48.