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"tea" can refer to any number of beverages including herbals like mint or chamomile. But 'true' tea that is packed with beneficial antioxidants is made from the leaves, stems and buds of the Camellia sinensis plant. This includes the varieties black, green, white or oolong tea, which all come from this bush. The difference between the teas is how they are processed. "green tea" is made from leaves that are dried right after harvesting, while the leaves used to make black tea are fermented for a short time. White tea leaves do not undergo any oxidation and are shielded from the sun and not allowed to produce any chlorophyll.
Health Benefits of Tea
Tea is a good source of flavonoids called catechins, which are important antioxidants that are associated with helping to prevent certain diseases. The majority of these catechins are found in green tea and include epigallocatechin-3-gallate (EGCG), the most abundant and widely studied tea polyphenol.
All of these teas contain caffeine and theanine (an amino acid), which affect the brain, and have shown to heighten mental alertness. Caffeine levels tend to be higher in tea bag forms (the finer grind releases more caffeine).
The more processed the tea leaves, usually the less polyphenol content. As oolong and black teas are oxidized or fermented, they have lower concentrations of polyphenols than green tea; but their antioxidizing power is still high.
Here's what some studies have found about the potential health benefits of tea:
Green tea: Made with steamed tea leaves, it has a high concentration of EGCG and has been widely studied. The antioxidants in green tea as associated with relieving conditions varying from simple viral or bacterial infections, to degenerative conditions including cancer, cardiovascular disease, stroke, osteoporosis and periodontal disease. Green tea has also shown to alleviate symptoms of illnesses such as diabetes, liver disease and arthritis.
Black tea: Made with fermented tea leaves, black tea has the highest caffeine content and forms the basis for flavored teas like chai, along with some instant teas. Studies have linked the consumption of black tea along with green tea in helping to reduce the risk of heart disease, by improving endothelial function (keeping the lining of the arteries open to allow more blood flow) and lowering blood pressure. The major polyphenols of black tea and green tea have also been shown to inhibit proteins which are closely associated with cancer tumor growth and metastasis (the spreading of cancer cells from one organ or tissue to another).
Boosts insulin activity: a study from the US found that green, black and oolong teas increased insulin activity by about fifteen-fold in tests using fat cells obtained from rats.
Weight loss: Preliminary research findings suggest that drinking tea has an effect on weight and fat accumulation in the body. Researchers found that green tea extract significantly increased energy expenditure and fat oxidation, and resulted in weight loss of modestly obese patients.
Herbal tea is not really tea; it is an infusion of herbs, fruits, flowers, seeds, or roots. As these infusions do not come from the Camellia plant, they therefore do not have its health promoting benefits. Their chemical compositions of herbal infusions vary widely depending on the plant used, but they do promote various other health qualities, and have relaxing and calming effects. Another advantage is that they are caffeine-free.
Limited research has been done on the health benefits of herbal teas, but here are some of the findings:
Rooibos (red tea): This is a South African herb that is fermented. Although it has flavonoids with cancer-fighting properties, medical studies have been limited.
Tips on Using Tea
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