Green Tea

Green Tea Introduction

Green Tea (Camellia Sinensis) is an evergreen shrub, characterized by thick dark green leaves. The plant itself is usually cultivated at heights approaching 8 feet. Green tea is now grown in Asia, Africa, and parts of the Middle East. [1] Despite popular belief, Green teas, Black teas, and Oolong teas come from the same plant. The differentiation between each is solely dependant upon the processing methods used. For example, Green tea is picked; the leaves are rolled and dried. Black tea is prepared the same way, except the leaves are fermented before they are dried, which causes them to turn black and to obtain a different flavor.

Green tea has been used for thousands of years as a beverage and therapeutic agent. In countries such as Japan and China, the drinking of teas has remained a commonality among the people of these countries. Most traditional uses of Green tea is focused on ritual, but has been used as a whole body tonic; used to rejuvenate one mind and to provide vitality for life.

Today, Green tea is prized because of its high antioxidant activity and harnesses the potential to treat and prevent many diseases, especially cancer. The primary constituents of Green tea that lend to its high antioxidant activity are the polyphenols. The most well known polyphenols are: catechins and gallocatechins. [2] Polyphenols are one sub grouping of a larger classification of molecules known as flavonoids. Flavonoids are well known for their antioxidant potential.

Green tea also contains several other constituents, such as tannins, that allow it to be a useful remedy for diarrhea. It also contains caffeine, vitamins, and minerals. Although not as high as amounts the amount found in coffee, the caffeine in Green tea has been shown to stimulate the central nervous system.

Green Tea Uses

Parts Used

Green Tea is prepared using unfermented leaves of the plant Camellia Sinensis.

Green Tea Uses

Green tea is most recognized for its cancer prevention and potential treatment action. Green tea is anti-mutagenic and anti-carcinogenic. [3] It has also exhibited anti-neoplastic activity for most tumor cell lines in a Petri dish and animal studies.

Human studies have shown that Green Tea can reduce the risk of cancer in smokers by decreasing the oxidative damage to cells. [4] Green tea has significant antioxidant activity, scavenging free radicals that can lead to several types of cancers.

Green tea may be helpful as an adjunctive treatment for prostate cancer. It can lower the PSA - a tumor marker used to monitor the progression and growth of prostate cancer. [5] Green tea may also prevent colorectal cancer by decreasing the amount of inflammatory mediators present in the cells. [6]

  • Green tea is an effective treatment, both topically and orally for cervical lesions. It may be cancer preventative due to its ability to regress cervical dysplasia of the mild and moderate type. Green tea may also be effective against lesions caused by the Human Papilloma Virus, a virus that is known to contribute to the development of cancer of the cervix and vulva. [7]
  • Green tea is considered a cardioprotective botanical. In study, it has been shown to decrease levels of LDL, or bad cholesterol levels, in the blood. [8] Green tea can also protect against the oxidation of LDL because of its powerful antioxidant activity. This can assists in preventing the development of atherosclerosis, a deadly disease characterized by the hardening and narrowing of arteries.
  • Green tea may also prevent dental cavities. It is anti-inflammatory on the tissues of the mouth. [9] The constituents found within Green tea also lend antibacterial activity, and may be effective at combating several of the most common bacteria known to cause dental cavities and infections of the gums; including E.coli, staph, and strep. [10]
  • Green tea has also recently been recognized for its ability to increase the metabolism of fat and decrease weight. Green tea is thermogenic in nature; increasing the oxidation of fat molecules in the body .[11] It may prove helpful in persons suffering from obesity and are trying to lose weight.
  • Green tea has also been shown to protect the skin from damage caused by UV exposure. [12] This may be particularly relevant for individuals who are sensitive to UV light, as well as in those at an elevated risk for developing skin cancer.

Green Tea Dosages

Different dosages of Green tea are used, and are considered dependant upon individual need. For daily antioxidant intake, 1 - 2 teaspoons of tea (3g of soluble components), steeped in 1 cup of water may be sufficient. This beverage can be drunk 1 - 4 times a day.

Higher dosages can be taken in capsule form to increase ones protection potential cancer development. The recommended dosage for this delivery forms ranges from 300 - 400 milligrams of polyphenols per day. Most of the Green tea supplements available in capsule form will be standardized to 80% total polyphenols or 55% epigallocatechin.

Worth mentioning, dosages as high as 800 mg of epigallocatechin or polyphenols have been taken per day for cancer prevention. These doses are safe, but do produce some side effects. [13]

Green Tea Toxicities and Contraindications

Side effects from the administration of increased dosages of Green tea or Green tea extracts include; excess gas, upset stomach, nausea, heartburn, abdominal pain, dizziness, headache, and muscle pain. [13] The excessive ingestion of Green tea can also result in CNS symptoms of anxiety, restlessness, jitters, and insomnia; primarily caused by caffeine content.

Green tea is thought to be safe in all populations, though its use in women who are pregnant or nursing should be limited because of the effects of caffeine on the developing baby.


1. Chevallier A. Encyclopedia of Herbal Medicine, 2nd Ed. 2000. Dorling Kindersley, New York: 181.

2. Green Tea. February 2005.

3. Phase I study of green tea extract in patients with advanced lung cancer. Cancer Chemother Pharmacol. 2005 Jan; 55(1); 33-38.

4. Hakim IA et al. Effects of increased tea consumption on oxidative DNA damage among smokers: a randomized controlled study. J Nutr. 2003 Oct; 133(10): 3303S-3309S.

5. Jaoti A et al. A phase II trial of green tea in the treatment of patients with androgen independent metastatic prostate carcinoma. Cancer. 2003 Mar 15; 97(6): 1442-1446.

6. August DA et al. Ingestion of green tea rapidly decreases prostaglandin E2 levels in rectal mucosa in humans. Cancer Epidemiol Biomarkers Prev. 1999 Aug; 8(8): 709-713.

7. Ahn WS et al. Protective effects of green tea extract (Polyphenon E and EHCG)on human cervical lesions. Eur J Cancer Prev. 2003 Oct; 12(5): 383-390.

8. Maron DS et al. Cholesterol lowering effect of a theaflavin enriched green tea extract: a randomized controlled trial. Arch Intern Med. 2003 Jun 23; 163(12): 1448-1453.

9. Krahwinkel T, Willershausen B. The effect of green tea chew candies in the degree of inflammation of the gingival. Eur J Med Res. 2000 Nov 30; 5(11): 463-467.

10. Rasheed A , Haider M. Antibacterial activity of camellia sinensis extracts against dental caries. Arch Pharm Res. 1998 Jun; 21(3): 348-352.

11. Dulloo G et al. Efficacy of green tea extract rich in Catechin polyphenols and caffeine in increasing 24-hour energy expenditure and fat oxidation in humans. Am J Clin Nutr. 1999 Dec; 70(6): 1040-1045.

12. Elmets CA et al. Cutaneous photo protection from ultraviolet injury by green tea polyphenols. J Am Acad Dermatol. 2001 Mar; 44(3): 425-432.

13. Chow HH. Pharmokinetics and safety of green tea polyphenols after multiple dose administration of epigallocatechin and polyphenon E in healthy individuals. Clin Cancer Res. 2003 Aug 15; 9(9): 3312-3319.