There is no clear evidence that green tea can help to cure cancer. Green tea is made from the dried leaves of the plant Camellia sinensis, and contains chemicals known as polyphenols. These are antioxidants that may help to prevent DNA damage caused by free radicals, and this is why some people think that tea can help to prevent or cure cancer. Some laboratory studies have shown that tea polyphenols can stop cancer cells from growing; however, studies in humans show variable results. In 2009, the internationally respected Cochrane Collaboration reviewed all the clinical studies on the effect of green tea on cancer prevention or death from cancer. The results were conflicting – some showed that green tea could help prevent cancer, some showed that it had no effect and some showed that it increased the risk of some cancers. Subsequent reviews and analyses found similar results. These results are uncertain because there have not been enough studies, the studies that have been done don’t include enough people, they used different amounts of tea, and they may not have accounted for other lifestyle factors that can affect cancer. This means that, overall, the studies on green tea and cancer are inconclusive for all types of cancer, and more large-scale clinical trials need to be done before we can be sure whether green tea helps to prevent or cure cancer. Drinking green tea in moderate amounts is not associated with any significant harmful effects. However, evaluations by the International Agency for Research on Cancer determined that drinking any very hot beverage (above 65°C) is probably a cause of oesophageal cancer. In order to minimise risk, leave hot drinks to cool for about four minutes after boiling before drinking.