What does Tea come from?
All tea (whether black, green or oolong) comes from the leaves of the Camellia sinensis plant. Camellia sinensis is evergreen and thrives in semi-tropical climates. There are reported to be over 2000 types of tea, the differences result from climate, the growing region, altitude, soil conditions and the style of processing the tea undergoes.
What is the difference between Green, Black and Oolong Teas?
The difference between green, black and oolong teas are a result of the type of processing the leaves of the Camellia sinensis undergoes. Black tea is produced when newly harvested leaves are cut and torn and exposed to the air. The leaves undergo a natural enzymatic process (fermentation) which changes the colour of the leaves from green to brown, and after further drying (firing) to black. With green tea, the leaves are typically heated with steam which stops the fermentation process. The leaves are then dried. The resulting tea produces the liquid that is pale green. Oolong tea is produced using the same process as black tea, however, the time of fermentation is shorter. Oolong tea produces a liquid that is midway, in flavour and colour, between green and black tea.
Are Herbal Teas the same as Black, Green and Oolong Teas?
No, herbal teas do not, in general, contain leaves from the Camellia sinensis (unless stated) and therefore are not true teas. Herbal teas are either pure or mixtures of plant leaves, flowers, roots, spices, fruit and flavours. A more accurate name for herbal tea is herbal infusion. Herbal infusions do not contain the same antioxidants found in tea produced from the Camellia sinensis. Since herbal infusions can come from a mixture of ingredients it is likely some contain antioxidant components.
What is the link between Tea & Health?
Tea is a rich source in antioxidants called flavonoids which may protect against free radicals. Free radicals damage healthy cells and tissues and are generated by normal body functioning and also external stimuli such as UV light, smoking and chemicals. Research suggests this damage may contribute to the development of chronic diseases and strokes. Antioxidants prevent the activity of free radicals. Emerging scientific evidence associates tea drinking with health benefits, however more scientific research is needed before conclusions can be made about the link between drinking tea and optimising health. Evidence to date suggests that drinking tea, in particular, may help maintain good cardiovascular function contributing to a reduced risk of cancer and heart disease.
What are the Antioxidants in Tea?
The main type of antioxidants are flavonoids. The amount and type of flavonoids in tea depend on the variety, manufacturing processes and brewing habit. Catechins, a group of flavonoids, are found in all teas but are particularly high in green tea. During the fermentation process of black tea, the catechins are converted to more complex flavonoids known as theaflavins (which provide the unique flavour of a particular tea) and thearubigens (which give the tea its liquor colour). Oolong tea contains antioxidants that are found in both green and black tea. Scientific research suggests that the flavonoids in green, black and oolong tea have similar antioxidant activity. Most scientific research has been based on the study of catechins because they can be easily isolated.
Does the addition of milk, lemon, sugar or artificial sweetener affect the antioxidant level?
Emerging evidence suggests that there is no effect on the absorption of the tea flavonoids or catechins. Research conducted by the CSIRO in 1997 also showed that the addition of milk to black tea did not affect the antioxidant activity.
Is the Antioxidant level in all tea the same?
Research suggests that tea grown in different regions contain varying levels of flavonoid antioxidants. The length of brewing time will affect the release of flavonoid antioxidants. The majority of flavonoids are released within two minutes of brewing. The method of brewing also affects the amount of antioxidant in each cup. Teabags which are moved within the cup tend to release the flavonoids faster than tea brewed in a teapot.
The flavonoids in tea like other compounds in food such as phytates in cereal partially inhibit iron absorption when consumed with food. Only iron from plant sources and not animal sources are affected. This effect can be reduced significantly by the inclusion of vitamin C rich food (eg orange juice). In western countries, there is no indication that tea consumption causes iron deficiency. Risk groups for iron anaemia (young children and pregnant women) are encouraged to eat diets rich in iron and vitamin C.
Does Tea effect cholesterol levels?
Most human trials have not shown a positive effect on blood cholesterol levels. In vitro (test tube) tests have shown that the antioxidant flavonoids in tea protect cholesterol from oxidation. It is the oxidation of cholesterol that is thought to contribute to the formation of arteriosclerosis.
Does Tea contain the same amount of caffeine as Coffee?
No, caffeine content in tea brewed to Australian conditions is about half that of brewed coffee. The caffeine level in tea depends on the method of preparation, brewing time and to some extent the variation of the tea plant itself. Green tea has the same amount of caffeine as black tea, however like all tea, the amount of caffeine is influenced by brewing time, preparation and the amount of leaves used. Caffeine content in tea can vary between 2 – 6% caffeine depending on the seasonal conditions prevalent at the time of harvesting.
Is caffeine dangerous?
Extensive research has found no association between moderate caffeine consumption and the risk of chronic disease. However, those who have caffeine intolerance should obviously avoid all foods and beverages that contain caffeine.
What are Tannins?
Tannin is a general term for flavonoids found in tea. Polyphenols is also a term that refers to a specific chemical structure of the antioxidant compounds in other foods. However, tea flavonols show specific antioxidant properties not found in other foods.
Does tea contain tannin?
No. The association of “tannin” with tea is actually a misnomer. The chemical components of tea sometimes referred to as “tannins” are actually polyphenols, not tannic acid.