Cancer:

Epigenetics concerns the control over the expression of genes, the ‘turning on and off’ of genes. Deregulation of epigenetic mechanisms plays an important role in cancer.(7,16) In addition to inhibiting tumor cell proliferation, inducing apoptosis and modulating signaling pathways critical for cancer cell transformation and survival, including MAPK (mitogen activated protein kinases), EGFR (epidermal growth factor receptor), IGF-1 (insulin-like growth factor) and NF-κB (nuclear factor-kappa B) signaling pathways, green tea catechins also inhibit tumor ingrowth into surrounding tissue, angiogenesis and metastasis, partly through inhibition of MMPs ( matrix metalloproteinases) and uPA (urokinase plasminogen activator).(4,19,41) The special thing about green tea catechins is that they only clear cancer cells, while healthy cells are left alone. Catechins probably work synergistically in this regard.(4,7,16)

Cancer Prevention

It is not entirely clear whether drinking green tea significantly lowers the risk of cancer. The results of human observational studies are inconclusive in this regard.(16,42,43) This may be related to the difficulty of determining exactly how many green tea catechins a person ingests each day (see safe intake of catechins). In addition, the daily intake of catechins is in many cases probably too low for significant protection. Consumption of at least 10 cups of green tea or its equivalent in supplement form may be required for (primary) cancer prevention. Japanese women who drink more than 10 cups of green tea a day are less likely to develop all forms of cancer; higher tea consumption is also associated with a lower risk of metastases and recurrence of breast cancer. (3) In a Japanese prospective study of 8552 participants, followed for 11 years, 488 people (285 men, 203 women) were diagnosed with cancer. Those who drank at least 10 cups of green tea daily had (compared to those who drank less green tea) a significantly lower risk of lung, colon and liver cancer in particular.(44) A Chinese case-control study (130 men with histologically confirmed prostate cancer, 274 healthy controls) showed that the risk of prostate cancer decreases significantly as men drink more green tea for a longer period of time, suggesting that green tea protects against prostate cancer. (45) Whether green tea protects against esophageal cancer is less clear.(7, 42) The beneficial effects of green tea may be negated by drinking tea too hot. Research has shown that tea that is too hot increases the risk of esophageal cancer by a factor of 3 to 4. (7) With regard to lung cancer, a meta-analysis indicates that green tea only protects non-smokers against this form of cancer. In non-smokers, an increase in green tea consumption by 2 cups a day is associated with an 18% reduction in the risk of lung cancer.(7,46) In a Chinese case-control study (649 women with lung cancer, 675 healthy controls) did not -smoking women who regularly drank green tea 35% less likely to develop lung cancer than non-smoking women who drank little or no green tea; this significant inverse association was dose dependent.(46,47) Research has shown that tea that is too hot increases the risk of esophageal cancer by a factor of 3 to 4. (7) With regard to lung cancer, a meta-analysis indicates that green tea only protects non-smokers against this form of cancer. In non-smokers, an increase in green tea consumption by 2 cups a day is associated with an 18% reduction in the risk of lung cancer.(7,46) In a Chinese case-control study (649 women with lung cancer, 675 healthy controls) did not -smoking women who regularly drank green tea 35% less likely to develop lung cancer than non-smoking women who drank little or no green tea; this significant inverse association was dose dependent.(46,47) Research has shown that tea that is too hot increases the risk of esophageal cancer by a factor of 3 to 4. (7) With regard to lung cancer, a meta-analysis indicates that green tea only protects non-smokers against this form of cancer. In non-smokers, an increase in green tea consumption by 2 cups a day is associated with an 18% reduction in the risk of lung cancer.(7,46) In a Chinese case-control study (649 women with lung cancer, 675 healthy controls) did not -smoking women who regularly drank green tea 35% less likely to develop lung cancer than non-smoking women who drank little or no green tea; this significant inverse association was dose dependent.(46,47) (7) With regard to lung cancer, a meta-analysis indicates that green tea only protects non-smokers against this cancer. In non-smokers, an increase in green tea consumption by 2 cups a day is associated with an 18% reduction in the risk of lung cancer.(7,46) In a Chinese case-control study (649 women with lung cancer, 675 healthy controls) did not -smoking women who regularly drank green tea 35% less likely to develop lung cancer than non-smoking women who drank little or no green tea; this significant inverse association was dose dependent.(46,47) (7) With regard to lung cancer, a meta-analysis indicates that green tea only protects non-smokers against this cancer. In non-smokers, an increase in green tea consumption by 2 cups a day is associated with an 18% reduction in the risk of lung cancer.(7,46) In a Chinese case-control study (649 women with lung cancer, 675 healthy controls) did not -smoking women who regularly drank green tea 35% less likely to develop lung cancer than non-smoking women who drank little or no green tea; this significant inverse association was dose dependent.(46,47) 675 healthy controls) non-smoking women who regularly drank green tea had a 35% lower risk of lung cancer than non-smoking women who drank little or no green tea; this significant inverse association was dose dependent.(46,47) 675 healthy controls) non-smoking women who regularly drank green tea had a 35% lower risk of lung cancer than non-smoking women who drank little or no green tea; this significant inverse association was dose dependent.(46,47)

cancer progression

In a limited number of human studies (chronic lymphocytic leukemia, precancerous prostate cancer, head and neck cancer, colon cancer, cervical cancer) a protective effect of green tea catechins (in doses up to 3000 mg green tea extract) on tumor progression has been established.(48- 52) In a group of men with pre-prostate cancer (HGPIN, high-grade prostatic intraepithelial neoplasia), supplementation with catechins (600 mg/day with 60% EGCG, for one year) significantly inhibited tumor progression compared to placebo (9% versus 30%), with significant improvement in IPSS (International Prostate Symptom Score) and quality of life.(48) The protective effect of catechin supplementation lasted for at least 2 years.(53) Green tea catechins are interesting for the prevention and treatment of (incipient) prostate cancer, especially because prostate cancer develops very slowly.(16,54) Italian researchers note that green tea catechins are increasingly used in men with non-advanced prostate cancer.(16)

The Pap smear (or PAP test) offers the possibility to detect early stages of cervical cancer. If the PAP test is abnormal, supplementation with green tea extract may be considered. Supplementation with EGCG (200 mg/day), especially in combination with an ointment containing EGCG, significantly improved cervical abnormalities (chronic cervicitis, mild dysplasia, moderate dysplasia and severe dysplasia) in 51 women infected with EGCG in a clinical study. the HPV virus.(52) EGCG fights cancer and also has an antiviral effect against the HPV virus.

For the time being, the use of green tea extract is not recommended during regular cancer therapy due to its antioxidant effect, although synergistic effects have been observed (such as with tamoxifen) and green tea extract in high doses may have pro-oxidative effects.(1)