The unfermented leaves of Camellia Sinensis offers benefits like brain power, lose fat and lowers cancer risk etc. You can easily  have 2-3 cups in a day for polyphenols.

Green tea has powerful antioxidants like polyphenols-flavonoids and catechins. These reduce free radical damage in the body.Green tea has powerful medicinal properties due to antioxidant

Epigallocatechin gallate (EGCG).It also has some important minerals. A low quality green tea has more fluoride.

1. It has a key active ingredient and stimulant Caffeine. It increases concentration of neurotransmitters like Dopamine and norepinephrine. Caffeine and L-theanine improve brain function. It improves mood, reaction time, memory and vigilance.
2. Studies have shown that green tea enhances fat burning .Green tea increases fat burning by 17% and energy output by 4%.It also burns fat stores for energy and improves physical performance.
3. Green tea protects against cancers particularly Breast cancer, Prostate cancer and Colorectal cancer.
4. Adding milk to green tea reduces the antioxidant value.
5. Green tea improves brain function in neurodegenerative disorders like Parkinson and Alzheimer’s and lowers their risk.
6. Studies show Green tea to improve dental health and lower bad breath, dental cavities and tooth decay. It discourages various viruses especially the Influenza virus and kills bacteria.
7. Green tea has shown to improve insulin sensitivity and reduce blood glucose.  Study in Japanese group has shown 42% lower risk of Type-2 Diabetes.
8. Green Tea drinkers have 31% lower risk of Cardiovascular disease. It protects LDL cholesterol oxidation and thus heart disease.
9. Green tea has shown decrease in belly fat. A controlled trial for 12 weeks showed significant decrease in body weight, abdominal fat, body fat  percentage and waist circumference.
10. Green tea raises longevity. A study in Japanese adults aged 65-84 yrs old showed 76% less chances of dying in 6 years study period. Death by stroke is lowered by 42% in women and 35% in men. Heart disease deaths are 31% less in women and 22% in men.

References:

Journ of Nutr 2008

Ann.Intern medicine 2006

Am journ of Clin nutr 2008

Atherosclerosis 2000

Karger 1991

Obesity June 2007

Annal of Epidemiol Oct 2009