Green tea is rich in a polyphenol called epigallocatechin-3-gallate (EGCG), with beneficial effects in human health shown by some studies including:
- Protection against oxidative damage
- Prevention against cáncer
- Lowering of blood colesterol level
- Lowering of blood sugar level
As shown by pharmacokinetic studies, EGCG (and other catechins found in tea) are rapidly and extensively metabolized both by human and gut microbial metabolism. Therefore, the biological effects of these polyphenols in humans are attributed to the resulting compounds (the metabolites) rather than to the parent compound (EGCG or other catechins).
One interesting characteristic of polyphenols is that they can act in two opposing ways: as an antibiotic and as a prebiotic. Whether they act as one or the other depends on the microbe. This means that for some microbes, polyphenols are a poison, killing them, and for others are food, supporting them. As a consequence, polyphenols select different species of microbes thus altering and shaping the gut microbiota when they are included in the diet.