Generally, tea is divided into
at least six different types based on how it is processed, which are white tea
(wilted and un-oxidized), yellow tea (un-wilted and un-oxidized, but allowed to
yellow), green tea (un-wilted and un-oxidized), oolong tea (wilted, bruised,
and partially oxidized), black tea (Chinese red tea, wilted, sometimes crushed,
and fully oxidized,) and post-fermented tea (Chines black tea). But the most
common ones are white, green, oolong, black and post-fermented tea.
Due to un-oxidized, green tea,
for example, reportedly contains the highest concentration of powerful
antioxidants called polyphenols, substances that fight free radicals (reactive
oxygen species, ROS), which
damage compounds in the body that change cells, damage DNA, and even cause cell
death. There are several polyphenols in green tea, including
epicatechin (EC), 2epicatechin-3-gallate (ECG), epigallocatechin (EGC), epigallocatechin-3-gallate
(EGCG), catechin, and gallocatechin (GC),
in which EGCG is the most abundant, accounts
for 65% of the total polyphenolic content.
Those polyphenols have a
number of health benefits and medical valuations. High polyphenol components in green tea are reportedly believed more effective antioxidants than Vitamins C and E and to contribute to the aging process and
development of a number of health problems, including cancer and heart disease.
Chinese people traditionally used green tea as to help body to rid of excess
fluid and to improve body conditions, including regulating body
temperature and blood sugar, promoting digestion, and improving mental
processes.
Clinical studies have suggested that antioxidant properties of green tea may help prevent atherosclerosis, particularly coronary artery disease, green tea lowers total cholesterol and raises HDL ("good") cholesterol in both animals and people and green tea may help protect against cancers, in which polyphenols is assumed to help kill cancerous cells and stop them from growing.
Clinical studies have suggested that antioxidant properties of green tea may help prevent atherosclerosis, particularly coronary artery disease, green tea lowers total cholesterol and raises HDL ("good") cholesterol in both animals and people and green tea may help protect against cancers, in which polyphenols is assumed to help kill cancerous cells and stop them from growing.
Many clinical studies suggest
that the polyphenols in tea, especially green tea, may play an important role
in the prevention of cancers, including bladder
cancer, breast cancer, ovarian cancer, colorectal cancer, esophageal cancer, lung
cancer, pancreatic cancer, prostate
cancer, skin cancer and stomach cancer.
Green tea has
also been reportedly suggested to help reduce inflammation, help prevent
the development of type 1 diabetes and slow the progression once it has
developed, to protect the liver from the damaging effects of toxic substances
such as alcohol, help treat viral hepatitis, an inflammation of the liver, help
to boost metabolism and help burn fat - combination of catechins (one of the
polyphenols ) and caffeine to help body weight loss.
In addition, the
metal-chelating properties of polyphenols (e.g., EGCG) are also important
contributors to their protective effects (such as the iron-chelating properties
of EGCG) in neurodegenerative diseases ,
such as Parkinson's disease due to misregulated iron metabolism. Furthermore, polyphenols (e.g., catechin) have been reported to effects on
several cellular and molecular targets in signal transduction pathways
associated with cell death and cell survival (neuronal cells and in tumour
epithelial/endothelial cells).
Molecular structure of EGCG.
Molecular structure of catachin, one of flavanols in green tea.
Molecular structure of EGCG.
Molecular structure of catachin, one of flavanols in green tea.