As cells function normally in the body, they produce damaged molecules — called free radicals. These free radicals are highly unstable and steal components from other cellular molecules, such as fat, protein, or DNA, thereby spreading the damage.

This damage continues in a chain reaction, and entire cells soon become damaged and die. This process is called peroxidation. Peroxidation is useful because it helps the body destroy cells that have outlived their usefulness and kills germs and parasites. However, peroxidation, when left unchecked, also destroys or damages healthy cells.
Antioxidants help prevent widespread cellular destruction by willingly donating components to stabilize free radicals. More importantly, antioxidants return to the surface of the cell to stabilize rather than damage other cellular components.

When there are not enough antioxidants to hold peroxidation in check, free radicals begin damaging healthy cells which, can lead to problems.

The Nutritional Value of Tea
In addition to valuable antioxidant properties and contributing to our daily fluid intake target of 2.5 litres, tea contains many vitamins, minerals and amino acids that includes

Vitamins: C, K, B12, B6 and E
Minerals: Trace amounts of potassium, manganese, magnesium, calcium
Amino Acids: Tea is a strong source of amino acids including L-theanine