Tea is the most commonly consumed beverage in the World after water. Tea has important health implications because research suggests that drinking tea confers protection against particular diseases including cardiovascular disease, obesity, type 2 diabetes, dementias and metabolic syndrome. The protective effects of tea against disease may stem from the antioxidants present in tea leaves, that are transferred to the water during brewing. In this respect the brewing conditions can influence this process. Evidence for example shows that traditional tea has an antioxidant capacity as high or higher than most fruits and vegetables of a dry weight basis. When 1.95 gram bags of green and black tea are added to 150 mL of boiling water, 85 % of the antioxidant activity is solubilised to the water in the first 5 min of brewing. Following this 5 min period, 13 % of the antioxidant activity is solubilised when the bag is placed in a new 150 mL glass of boiling water following the same 5 min brewing time.
The antioxidant ability of tea compares well fruits and vegetables. Berry tea also contains substantial amounts of antioxidants. Drinking both traditional and berry teas can therefore provide significant levels of antioxidants to the diet. Because the antioxidants in traditional tea and berry tea differ, combining the two provides a wider range of antioxidant types, and this may confer a greater level of protection than from drinking only a single type of tea. Green tea is available with a number of other substances including citrus fruits and berries and this may significantly increase the number of different antioxidants present in the tea. A number of studies have shown that black tea can have higher antioxidant activity than green tea, although this depends on the method used to measure the antioxidants. However, studies on berry tea show that its overall antioxidant capacity is close to that of traditional tea, making it a viable beverage to increase antioxidant intake.
Stirring and agitating the water has been shown to significantly speed the release rate of the antioxidants to the water from tea leaves. And this is how most people make tea. After the first brewing the amount of antioxidants in tea compare well with the antioxidant amounts found in fruits and vegetables suggesting that traditional tea can make a significant contribution to total antioxidant intake. Berry teas also provide significant amounts of antioxidants, although the types of antioxidants vary considerably between traditional and berry teas. Traditional tea contains a number of polyphenolic antioxidants including gallic acid, chlorogenic acid, flavan-3-ols (catechin and epicatechin) as well as flavonols (quercetin, kaempferol and myricetin). Berry teas contain high amounts of other polyphenolic antioxidants, particularly the anthocyanins, which are found in high concentrations in berries. Berry tea also contains higher levels of vitamin C than traditional teas, as vitamin C is also found in high amounts in berries.
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