according to the national cancer institute , The polyphenols in tea have been shown to decrease tumor growth in laboratory and animal studies and may protect against damage caused by ultraviolet UVB radiation.
In countries where green tea consumption is high cancer rates to be lower, but it is impossible to know for sure whether it is the green tea the prevents cancer in these specific populations or other lifestyle factors.
One large-scale clinical study compared green tea drinkers with non-drinkers and found that those who drank the most tea were less likely to develop pancreatic cancer ,particularly women, who were 50% less likely to develop the disease
Studies have also show the positive impacts of green tea on breast , ovarian ,colorectal , esophageal ,lung ,prostate ,skin and stomach cancer.
Researchers believe that it is the high level of polyphenols in tea that help kill cancerous cells and stop them from growing, however the exact mechanisms by which tea interacts which cancerous cells is unknown.
Other studies have shown a lack of preventative effects of tea on cancer. The amount of tea required for cancer-preventive effects has also varied widely in studies-form 2-10 cups per day.
In 2005 , the FDA stated that “ there is no credible evidence to support qualified health claims for green tea consumption and reduced risk of gastric, lung, colon/rectal, esophageal, pancreatic, ovarian, and combined cancers.”