Let me give you some scientific facts on tea. The information will enable you to appreciate the health benefits of this herb popular in many parts of the world.
There are two popular varieties of this plant Camellia sinensis var assamica and Camellia sinensis var sinensis.
The most well-known chemical constituent of tea is caffeine, which is 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. These chemical compounds help defend the plant against insects and pests. Theobromine and theophylline are responsible for the bitterness of the tea.
Theanine in green tea plays a role in reducing stress. Oxidized catechins (theaflavins in black tea) are said to 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 signal of satiation to the brain).
In summary, tea may not be an immunity booster but has many medicinal properties.