Oxidative damage may trigger several cancer types. As a rich source of antioxidants, Green Tea Factory may help prevent them .
Colorectal Cancer
In an observational study on almost 70,000 Chinese women, regular consumption of green tea was associated with a reduced incidence of colorectal cancer.
Although they generally concluded that the evidence was insufficient and larger, better-designed clinical studies were needed, 4 meta-analyses associated drinking green tea with a lower incidence of colorectal cancer.
In 2 clinical trials on 276 people, supplementation with green tea extract reduced the incidence of a colorectal cancer type (metachronous colorectal adenoma).
Breast Cancer
In a study on over 4,000 French women, consuming green tea and other antioxidant beverages was associated with a lower incidence of breast cancer. However, a study on over 1,500 women failed to associate regular green tea intake with breast cancer.
In a small clinical trial on 12 women with breast cancer, a formulation with epigallocatechin gallate efficiently delivered this polyphenol into the blood and tumors and reduced a biomarker of breast cancer (Ki-67).
Meta-analyses found a slight trend towards reducing breast cancer incidence in women drinking high amounts of green tea, although they generally considered the evidence insufficient due to the high heterogeneity of the studies. The most recent meta-analysis did find green tea effective at protecting from breast cancer, especially from its recurrence.
Prostate Cancer
In an observational study on almost 50,000 Japanese men, green tea consumption was associated with a reduced frequency of advanced prostate cancer.
Two meta-analyses concluded that green but not black tea may help prevent prostate cancer, especially in Asians and in people taking over 7 cups/day. However, another meta-analysis of 21 studies found no association.
In a clinical trial on 60 men with a condition that often develops into prostate cancer (high-grade prostate intraepithelial neoplasia), the daily treatment with green tea catechins helped prevent this type of cancer. However, a similar trial on almost 100 men at risk of prostate cancer found green tea ineffective as a preventive measure. Nevertheless, a meta-analysis of 13 studies found green tea slightly effective.
Although they reduced the levels of a prostate cancer marker (PSA) in some studies, green tea polyphenols had little or no effectiveness in preventing prostate cancer in most trials on people without high-grade prostate intraepithelial neoplasia. One of them even associated green tea supplements with an increased incidence.
Liver Cancer
Green tea polyphenols reduced liver cancer biomarkers in 2 clinical trials on over 200 people at high risk of developing this condition.
Three meta-analyses found an association between green tea intake and reduced incidence of primary liver cancer.
Lung Cancer
In 2 clinical trials on over 200 heavy smokers, drinking green tea reduced oxidative damage to the DNA, possibly reducing the risk of lung cancer.
Three meta-analyses concluded that green tea may protect against lung cancer.
However, a small trial on 17 people with advanced lung cancer found green tea ineffective as a chemotherapeutic agent.