Green tea contains many volatile oils, vitamins, and minerals, as well as caffeine. The part responsible for its medicinal value, however, is polyphenols, including catechins.¹ Green Tea acts as an antioxidant,² which can help protect the body from many diseases.

Useful in treatment of:
Heart disease : It lowers cholesterol, reduces platelet aggregation (clumping), and lowers blood pressure,³ all of which may contribute to decreasing risk of heart disease.

Cancer Prevention: Evidence is increasing that consumption of green tea may have beneficial effects on prevention of several cancers, including colon, pancreatic and stomach.⁴

Green tea may stimulate the immune system to help defend the body against bacterial infections, including dental plaque.⁵ Green tea has antibacterial properties and stimulates the production of immune cells.^6,7

When taken in large quantities (more than ten cups daily), it appears to protect against liver damage.⁸ However, since such high levels of caffeine can cause other complications, this therapy should not be undertaken without a health provider’s consultation.

Recommended Dosage: Three cups daily. Capsulized extracts are available, and a typical dosage is 100 to 150 mg 3 times daily of a green tea extract standardized to contain 80% total polyphenols and 50% epigallocatechin gallate. The efficacy of these preparations compared to the consumption of the tea itself is not known at this point.

Contraindications: Green tea contains caffeine. Individuals with conditions that may be complicated by high caffeine intake (including insomnia, depression, and pregnancy) should speak with a health professional before adding green tea to their diet. People taking the class of antidepressant called MAO inhibitors may want to avoid the caffeine in green tea.

References:
¹Graham HN. Green tea composition, consumption, and polyphenol chemistry. Prev Med 1992;21:334–50.
²Serafini M, Ghiselli A, Ferro-Luzzi A. In vivo antioxidant effect of green tea in man. Eur J Clin Nutr 1996;50:28–32.
³Stensvold I, Tverdal A, Solvoll K, et al. Tea consumption. Relationship to cholesterol, blood pressure, and coronary and total mortality. Prev Med 1992;21:546–53.
⁴Imai K, et al. Cancer-preventive effects of drinking green tea among a Japanese population. Prev Med 26(6): 769–775, 1997
⁵Hamilton-Miller JM. Antimicrobial properties of tea (Camellia sinensis L.). Antimicro Agents Chemother 1995;39(11):2375–77.
⁶You SQ. Study on feasibility of Chinese green tea polyphenols (CTP) for preventing dental caries. Chin J Stom 1993;28(4):197–199.
⁷Hamilton-Miller JM. Antimicrobial properties of tea (Camellia sinensis L.). Antimicro Ag Chemo 1995;39(11):2375–2377.
⁸Imai K, Nakachi K. Cross sectional study of effects of drinking green tea on cardiovascular and liver diseases. BMJ 1995;310:693–96.