Tea is found to be, second only to water as the
healthiest beverage of choice for a healthy diet. What makes tea a healthy
beverage are the polyphenolic antioxidants called catechins found within.
Antioxidants are substances that protect our bodies from the damage caused
by free radicals. Free radicals are chemical compounds that can cause
damage to the cell and bring about various health problems such as aging
and cancer. Free radicals are results of over exposure to ultra-violet
rays, pollution, food additives and preservatives.
The most common forms of catechins are catechins, epicatechins,
gallocatechins, epigallocatechins, and catechin gallates (e.g.
epigallocatechin gallates [EGCG]), the most abundant catechins in
green tea.
Catechins comprise almost 25% of the dry weight of
the fresh tea leaf. All true teas such as
white tea, green tea, oolong tea, and black tea contain
catechins. The levels of catechins differ in each type of tea because of
the processing techniques used to produce the tea. Unfermented teas such
as green tea and white tea contain higher levels of catechins than the
fermented teas like oolong tea and black tea. This is because catechins
are converted into polymerized catechins such as theaflavins and
thearubigins, both of which also act as antioxidants, during fermentation
process of the tea leaves.
Catechins in tea are believed to have antioxidant,
anti-cancer, anti-inflammatory, anti-viral, and anti-bacterial effects. Catechins
in tea act as antioxidants by neutralizing the overly reactive
oxygen-containing free radicals in the body thus preventing cellular
damage caused by oxidative stress. Oxidative stress has been connected to
cancer, cardiovascular diseases, aging, inflammation, and
neurodegenerative diseases such as Parkinson’s and Alzheimer. Catechins,
particularly in green tea have been found to help prevent malignant
transformation and tumour growth. Green tea catechins such as
epigallocatechin gallates (EGCG) also inhibit the oxidation of the “bad”
low density lipoprotein (LDL) cholesterol thereby helping prevent
occurrence of heart attack and stroke.
Tea and Cardio Health
In the 2006 issue of the Journal of American Medical Association, a study
conducted by the Tohoku University School of Public Policy in Japan showed
that participants who consumed at least five cups of green tea per day had
a 16-26 percent lower risk of mortality due to cardiovascular diseases and
stroke. The research has shown that the catechins in tea may have helped
in the improvement of the blood vessels and endothelial functions as well
as the cholesterol levels.
Statistics have shown that incidence of cardiovascular diseases among
Chinese is almost 80% lower than those people from developed countries,
China being a leader in green tea consumption
Tea and Cholesterol
A study conducted by the researchers in the United States Department of
Agriculture has shown that levels of “bad” LDL (low density lipoprotein)
cholesterol was reduced by 11.1% and total cholesterol by 6.5% in adults
that drank at least five servings of black tea. The study was published in
the 2003 issue of the Journal of Nutrition. Another study that appeared in
the Archives of Internal Medicine in the same year claimed that green tea
had the same cholesterol lowering effect. Consumption of green tea reduced
the LDL cholesterol and total cholesterol by 16.4% and 11.3% respectively.
Tea and Cancer
In a Swedish study that appeared in the 2005 issue of Archives of Internal
Medicine, women who consumed two or more cups of tea had a 46% lower risk
of contacting ovarian cancer than non-tea drinkers. Likewise, a 2003
research that was published in the International Journal of Cancer found
that women who drank green tea had a significant lesser risk of breast
cancer than non-tea drinkers.
Tea, Fat Metabolism and Weight Loss
Catechins along with caffeine in green tea are found to increase energy
expenditure. A study that involved 35 Japanese men showed that consumption
of oolong tea with green tea extract for three months resulted in the
reduction of body weight by 5.3 pounds on the average, decrease in body
mass index (BMI), fat absorption, and waist line. In a study conducted at
the University of Geneva in Switzerland researches found that catechin
polyphenols in green tea increased thermogenesis, the rate at which
calories are burned and heat is produced.
Tea and Diabetes
The polyphenols called catechins in green tea are found to lower
blood sugar. Researchers at the United States Department of Agriculture
have found that epigallocatechins gallate (EGCG) in green tea
improves the action of insulin thus helps prevent type 2 diabetes
