The prevention of cancer through dietary intervention is receiving considerable attention. Several epidemiological studies indicate that green tea has a protective effect against a variety of malignant disorders such as lung cancer, breast cancer and prostate cancer. This preventive potential of green tea against cancer is attributed to the biologically active flavonoids called catechins.

Epigallocatechin 3-o-gallate, EGCG, is the major catechin found in green tea. Another catechin is GCG, gallocatechin-3-gallate. Other catechins include epicatechin gallate (ECG), epigallocatechin (EGC), and epichtechin (EC). The relative concentration of the five major tea catechins are EGCG > ECG > EC > EGC > C.

Green Tea Extract, 100 mg ( Yielding 35 mg EGCG ), 60 Tablets

Green Tea Extract offers a convenient way to get the benefits of green tea catechin EGCG in a highly concentrated green tea pill form.  This green tea extract is standardized for bioflavonoid-like antioxidants known as polyphenols, particularly Epigallocatechin Gallate which has been found in scientific studies to be a potent antioxidant. Green tea antioxidants are likely to become more popular with time.

Supplement Facts
Green Tea Extract Yielding 70 mg EGCG catechin

Purchase Green tea extract

Suggested Use: One tablet two or three times a week in the morning or midday with a meal. Evening use may lead to mild insomnia. I do not suggest you take this pill every day, it is a good idea to take breaks from use.

Catechins and cancer, is there a connection?
Catechins exert diverse physiological effects against proliferative diseases by several mechanisms, most of which are not completely characterized.

Prostate Cancer
Chemoprevention of human prostate cancer by oral administration of green tea catechins in volunteers with high-grade prostate intraepithelial neoplasia: a preliminary report from a one-year proof-of-principle study.
Cancer Research. 2006.
Recent studies showed that 30% of men with high-grade prostate intraepithelial neoplasia (HG-PIN) would develop prostate cancer within 1 year after repeated biopsy. This prompted us to do a proof-of-principle clinical trial to assess the safety and efficacy of green tea catechins for the chemoprevention of prostate cancer in HG-PIN volunteers. The purity and content of GTCs preparations were assessed by high-performance liquid chromatography [(-)-epigallocathechin, 5%; (-)-epicatechin, 12%; (-)-epigallocatechin-3-gallate, 51%; (-)-epicatechin-3-gallate, 6%; total green tea catechins, 75%; caffeine, <1%]. Sixty volunteers with HG-PIN, who were made aware of the study details, agreed to sign an informed consent form and were enrolled in this double-blind, placebo-controlled study. Daily treatment consisted of three green tea catechin capsules, 200 mg each (total 600 mg/d). After 1 year, only one tumor was diagnosed among the 30 green tea catechins -treated men (incidence, approximately 3%), whereas nine cancers were found among the 30 placebo-treated men (incidence, 30%). Total prostate-specific antigen did not change significantly between the two arms, but green tea catechins -treated men showed values constantly lower with respect to placebo-treated ones. International Prostate Symptom Score and quality of life scores of green tea catechins -treated men with coexistent benign prostate hyperplasia improved, reaching statistical significance in the case of International Prostate Symptom Scores. No significant side effects or adverse effects were documented. To our knowledge, this is the first study showing that green tea catechins are safe and very effective for treating premalignant lesions before prostate cancer develops. As a secondary observation, administration of green tea catechins also reduced lower urinary tract symptoms, suggesting that these compounds might also be of help for treating the symptoms of benign prostate hyperplasia.

Diabetes, blood sugar
British Journal of Nutrition. 2014. Acute ingestion of catechin-rich green tea improves postprandial glucose status and increases serum thioredoxin concentrations in postmenopausal women.

Platelet Aggregation
Complex effects of different green tea catechins on human platelets.
FEBS Letters. 2003.
Epigallocatechin gallate (EGCG), a major component of green tea, has been previously shown to inhibit platelet aggregation. The effects of other green tea catechins on platelet function are not known. Pre-incubation with EGCG concentration-dependently inhibited thrombin-induced aggregation and phosphorylation of p38 mitogen-activated protein kinase and extracellular signal-regulated kinases-1/2. In contrast EGCG stimulated tyrosine phosphorylation of platelet proteins, including Syk and SLP-76 but inhibited phosphorylation of focal adhesion kinase. Other catechins did not inhibit platelet aggregation. Interestingly, when EGCG was added to stirred platelets, a tyrosine kinase-dependent stimulation of platelet aggregation was observed. The two other catechins containing a galloyl group in the 3' position (catechin gallate, epicatechin gallate) also stimulated platelet aggregation, while catechins without a galloyl group (catechin, epicatechin) or the catechin with a galloyl group in the 2' position (epigallocatechin) did not.

Potential harm or side effects
High concentrations of catechins when ingested in high doses for prolonged periods have been implicated in liver harm, but this is not yet proven.

Research
Green tea extract and catechin ameliorate chronic fatigue-induced oxidative stress in mice.
J Med Food. 2005.
Chronic fatigue syndrome (CFS) is an illness characterized by persistent and relapsing fatigue, often accompanied by numerous symptoms involving various body systems. The etiology of CFS remains unclear, but a number of studies have shown that oxidative stress may be involved in its pathogenesis. The present study was designed to investigate the protective effect of green tea extract and catechin in the mouse model of CFS. Animals were subjected to a forced swimming test session of 6 minutes every day for 7 days; a significant increase in immobility time on successive days represented the CFS in mice. Biochemical analysis revealed that the chronic swim test significantly increased lipid peroxidation levels and decreased glutathione levels in mouse whole-brain homogenate. Treatment with green tea extract (25 or 50 mg/kg, i.p.) and catechin (50 or 100 mg/kg, i.p.) for 7 days reversed the increase in immobility time. Protection was correlated with the lowered levels of lipid peroxidation and restoration of reduced glutathione levels in the brains of fatigued mice. These findings strongly suggest the pivotal role of oxidative stress in the pathophysiology of CFS and that green tea extract and catechin could be used as potential agents in the management of CFS and warrant the inclusion of green tea extract and catechin in the treatment regimen of CFS patients.

Catechins are the major source of flavonoids in a group of Australian women.
Asia Pac J Clin Nutr. School of Public Health, Queensland University of Technology, Kelvin Grove, QLD Australia.
Evidence is emerging for the role of flavonoids in the prevention of degenerative diseases such as cancer and cardiovascular disease. To determine the dietary intake of flavonoids in a group of Australian women. Twelve day weighed record data were available from 24 healthy young women, participating in a larger study on diet and hormones;. Dietary data were analysed for intake of 15 individual flavonoids, comprising four major subclasses: flavonols (quercetin, kaempferol, myricetin and fisetin), flavones (apigenin and luteolin), flavanones (hesperetin, naringenin and eriodictyol) and flavanes or catechins (epicatechin, epicatechin 3-gallate, epigallocatechin, epigallocatechin 3-gallate, catechin, gallocatechin). As limited data are available for the flavonoid content of Australian food and drink items, values were mainly sourced from published international data; intake was estimated utilising data for the aglycone form and for a limited number of glucosides converted to aglycone equivalents. Mean (SEM) daily intake in the group was 25.6 mg/d for flavonols, 3.9 mg/d for flavones, 22 mg/d for flavonones and 76 mg/d for catechins; total intake of flavonoids was 128 mg/d. Major food sources in this group of women were: onions, apples (with skin), tea (green, black), olives and broccoli, for flavonols; fresh parsley and celery, for flavones; oranges, grapefruit and their juices, for flavonones; and tea (green, black), apples (with or without skin), red wine, dark chocolate and cocoa, for catechins. To our knowledge these results are the first Australian data available on flavonoid intake. Catechins were the major subclass of flavonoids in this group of women, providing 59% of the total intake, followed by the flavonols (20%) and flavonones (18%), and with a smaller contribution from the flavones (3%). Our mean catechin intake was higher than that reported in Finnish (14 mg) or American (25 mg/d) populations, and comparable to that in a Dutch population (72 mg/d).

Questions
I read an article online that made these claims, "Did you know that most of the free-radical fighters in green tea never make it to your bloodstream? But there's a solution. To get a better grasp on the healthy catechins in your green tea, flavor your cup with a squeeze of citrus juice. The antioxidants in green tea famous for lowering your risk of chronic disease -- quickly lose their power in your intestine. In fact, as much as 80% of the catechins in green tea are never absorbed. The solution to boosting absorption is as simple as flavoring your tea with freshly squeezed and strained lemon, orange, lime, or grapefruit juice. The vitamin C in citrus may help with absorption by increasing the acidity in your small intestine. Other unidentified substances in the juice probably lend a hand, too. Researchers found a 50-50 mix had the greatest catechin-preserving effect, and lemon did it best, closely followed by orange, lime, and, in last place, grapefruit."
    This seems reasonable. You could add concentrated lemon juice, preferably organic, that is sold in health food stores, or if you have time you can squeeze half a lemon in your green tea mix and then sweeten it with stevia liquid.