Along with caffeine, which gives green tea its characteristic taste, bitterness, and stimulating effect, green tea is also rich in a group of chemicals, called catechin polyphenols (commonly known as tannins, which contribute to bitter taste and astringency). These catechin polyphenols include catechin, epicatechin, epicatechin gallate (ECG), epigallocatechin gallate (EGCG), and various proanthocyanidins. They are also known as flavonoids and are very powerful antioxidants. Flavonoids, together with some amino acids like thiamine, are responsible for the potent flavor of green tea.
Those magical catechins also have tons of potential in helping people with heart issues. “Catechins present in green tea have the ability to prevent atherosclerosis, hypertension, endothelial dysfunction, ischemic heart diseases, cardiomyopathy, cardiac hypertrophy and congestive heart failure by decreasing oxidative stress, preventing inflammatory events, reducing platelet aggregation and halting the proliferation of vascular smooth muscle cells,” explains the author of the study, published in the Chinese Journal of Natural Medicines.
One of the primary reasons for the popularity and consumption of all kinds of tea by human civilizations is its stimulating effect. This effect, again, is due to the caffeine and tannins present in the tea leaves. Caffeine and tannins, despite their potentially adverse effects on health, in the long run, act as very powerful stimulants. That is why a cup of tea makes you feel fresh and highly energized. Tea is an easy and ideal solution to counter fatigue, laziness, sleepiness, and lack of energy, and to improve blood circulation. This is why it is so popular with a wide variety of people in various industries, including professionals, housewives, students, and anyone else who has ever felt a bit drowsy during the day!

Several population-based clinical studies have shown that both green and black teas may help protect against cancer. Early clinical studies suggest that the polyphenols in tea, especially green tea, may play an important role in the prevention of cancer. Researchers also believe that polyphenols help kill cancerous cells and stop them from growing.
Rooibos tea is anti-inflammatory in nature, which means that it reduces blood pressure and scavenges free radicals like other antioxidants. Quercetin, another powerful antioxidant found in rooibos tea, has been linked to preventing a wide variety of heart conditions. It promotes an increase in HDL cholesterol (good cholesterol) and inhibits the LDL cholesterol (bad cholesterol) from binding to the walls of arteries and blood vessels. 
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