Let us look at the evidence-based properties of tea.
Black tea is a fermented tea, while green tea comes from the plant’s dried leaves.
The most well-known chemical constituent of tea is caffeine, stimulating in nature. Caffeine in tea is approximately 4 percent in dry weight. Tannin is the other principal constituent of tea.
Caffeine, theobromine, and theophylline are polyphenols belonging to the phenolic group of compounds. Theobromine and theophylline are responsible for the bitterness of the tea.
The major flavonols in tea are- catechin, epicatechin, epicatechin gallate, gallocatechin, epigallocatechin, and epigallocatechin gallate. Epigallocatechin gallate is the most active of these catechins. Another compound – L-theanine, is an amino acid found in tea. Theanine in green tea plays a role in reducing stress. Oxidized catechins (theaflavins in black tea) reduce cholesterol levels in the blood.
Tea decreases lipid and carbohydrate absorption, increases lipid metabolism, inhibits de novo metabolic production of fat, and increases carbohydrate utilization. (Grove et al., 2010) Green tea intake is associated with increased weight loss due to diet-induced heat generation attributed to the catechin epigallocatechin gallate. (Shixian et al., 2006)
High caffeine intake was associated with weight loss through heat and fat oxidation and suppressed leptin in women. (Leptin is a molecule that triggers a satiation signal to the brain). The green tea-caffeine mixture improved weight management in habitually low caffeine consumers, partly through heat generation and fat oxidation. (Westertep-Plantenga et al., 2005)
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