Tea is a popular beverage consumed worldwide. Drinking tea regularly is thought to benefit your health in a number of ways and may help prevent cardiovascular disease and stroke, lower your risk of dementia and certain cancers, and even help you live longer.
Tea comes from the plant Camellia sinensis. Three common types of tea are green tea, black tea,
and oolong tea. These teas differ in the way they are produced and processed. Green tea is not
fermented, for example, whereas black tea is fermented and oolong is semi-fermented.
Tea contains a range of chemicals including polyphenols, alkaloids such as caffeine, and other
compounds. The chemical composition of tea varies based on the species of plant, the season, the
climate and differences in the way the tea plants are grown, harvested and processed.
Polyphenols are the main active chemical compounds found in tea and these are thought to provide
its health benefits. Polyphenols are micronutrients found in plants and are powerful
antioxidants that help to prevent and reverse cell damage. They help protect your body against
oxidative stress that causes cell and tissue damage, which increases your risk of developing
chronic diseases. Tea also has anti-inflammatory properties.
Polyphenols include flavonols, theaflavins, catechins and more. The total amount of polyphenolic
compounds in green and black tea is similar, but the type of compounds varies. Green tea is
richer in catechins (including epigallocatechin-3-gallate (EGCG), epigallocatechin,
epicatechin-3-gallate and epicatechin, gallocatechins and gallocatechin gallate), whereas black
tea contains thearubigins, theaflavins, flavonols and catechins.
Drinking a moderate amount of tea significantly reduces your risk of dementia, including
Alzheimer’s disease and vascular dementia, according to the results of a large study that
followed 377, 592 people for about 9 years.
Participants who drank 1 to 4 cups of tea a day were 16 to 19 percent less likely to develop
Alzheimer’s disease. Vascular dementia was also reduced by 25 to 29 percent in participants who
drank 1 to 6 cups of tea a day. Drinking more tea, however, was not associated with any
additional benefit.
Drinking three cups of tea a day was found to provide the strongest protection against dementia.
Middle-aged participants and men appeared to benefit the most.
Drinking 2 or more cups of tea a day resulted in a modest decrease in the risk of dying among
nearly 500,000 participants in a study who were followed-up for a median of 11.2 years after
completing a questionnaire about their tea intake. The study looked at death from all causes,
including cancer, cardiovascular disease, ischemic heart disease, stroke and respiratory
disease.
The researchers commented that the results suggest tea can be part of a healthy diet, even when
quite a lot is consumed.
People who drank 1 to 3 cups of green tea a day were found to have a reduced risk of heart attack
and stroke compared with people who drank less than a cup of green tea a day, when researchers
looked at the results from 9 studies involving nearly 260,000 participants.
Various studies have also shown that the polyphenolic compounds in tea may help prevent
atherosclerosis, the build-up of plaque in your arteries, and reduce ‘bad’ low-density
lipoprotein (LDL) cholesterol. Tea may also help slow the natural decrease of ‘good’
high-density lipoprotein (HDL) cholesterol that happens as you get older. Regular long-term
consumption of black tea may even lower your blood pressure, helping to keep your heart healthy.
Although results from studies have been inconclusive, drinking tea, especially green tea, may
also help prevent or slow the growth of cancer. It’s not known exactly how tea helps, but it may
be due to its antioxidant properties.
Some studies have linked tea drinking to a reduction in the risk of certain cancer including
colon, lung, prostate, ovary, breast and other cancers.
An analysis of several studies conducted in participants with breast cancer indicated that
drinking three or more cups of green tea a day may lower the recurrence of breast cancer,
particularly in women that have stage I or II breast cancer.
A high intake of green tea (> 10 cups/day) was also associated with a lower risk of colon,
liver, and lung cancers.
The benefits of black tea on cancer have not been studied as extensively as green tea. However,
a small study found that people consuming hot black tea with citrus peel had a significant
reduction in squamous cell carcinoma of the skin, a type of skin cancer.
Black tea may also help reduce the risk of colon cancer and may provide a protective effect
against lung cancer in non-smoking women.
Tea may also help prevent diabetes mellitus and complications such as diabetic retinopathy and
diabetic nephropathy. The antidiabetic properties of tea are attributed to the theaflavins,
catechins, polysaccharides and caffeine it contains.
Tea may help to lower your risk of diabetes in a number of ways, such as by inhibiting
inflammation, promoting the production and secretion of insulin, and improving insulin
resistance and sensitivity.
According to the combined results of 17 trials involving 1133 participants, green tea lowers
fasting glucose levels and hemoglobin A1c (Hb A1c) concentrations. Hb A1c is measured to assess
how well diabetes is being controlled over time.
The Women's Health Study, which included 39,876 women aged 45 years and older, found that women
who drank 4 or more cups of green tea per day had a 30 percent lower risk of type 2 diabetes
than women who did not drink tea.
Consuming 3 or more cups of tea per day may help prevent the onset of rheumatoid arthritis,
according to the results of a study involving 31,336 women. Rheumatoid arthritis is an
autoimmune disease that causes joints to become inflamed and the surrounding cartilage and bone
to be worn away. The disease affects more women than men.
Tea also appears to help increase bone mineral density in older women. Low bone density can
cause people with rheumatoid arthritis and others to be more at risk of fractures and
osteoporosis, a condition that weakens bone.
The anti-inflammatory properties of tea may help reduce the inflammation associated with
rheumatoid arthritis.
