Green tea extract has many naturally occurring biological components of which polyphenolic epicatechins (ECs) are predominantly active. These include (–)-epigallocatechin-3-gallate (EGCG), (–)-epigallocatechin (EGC), (–)-epicatechin-3-gallate (ECG), and (–)-EC. The EC and EGC are catechol catechins, EGC and EGCG are pyrogallol catechins, and ECG and EGCG are gallate catechins.
So far green tea was shown to have many impacts in carbohydrate metabolism. Epidemiologic studies have shown that the consumption of green tea may reduce bodyweight and fat accumulation by improving glucose and lipid metabolism, and it has also been shown that green tea extract and EGCG ameliorate hyperglycemia and insulin resistance in humans and animals.
Green tea is considered as an alternative medicine for diabetes mellitus. The pathology of diabetes mellitus is caused by reactive oxygen species that activate the non-enzymatic glycation of proteins (leads to structural and functional changes), the aldose reductase pathway (causes sorbitol accumulation) and oxidative stress (results in protein, DNA and lipid damage).
Polyphenols in green tea reduce carbohydrate digestion and absorption in the intestine by inhibiting carbohydrate digesting enzymes and inhibiting glucose transporters across the intestine.
The anti-oxidant effect of green tea is because of its polyphenol cathechine components to scavenge ROS. Catechins from tea suppress the absorption of glucose from the small intestine by inhibiting α-glucosidase activity.
They are also shown to increase secretion of insulin by pancreatic β cells and protect cytokine induced inflammatory damage of these cells. Increasing insulin activity and maintaining glucose homeostasis are other mechanisms by which green tea is involved in carbohydrate metabolism.
Green tea can reduce the risk of developing diabetes
