The connection between green tea and cancer is the subject of a great deal of scientific research that has been largely inconclusive, although some evidence seems to suggest that the antioxidants in green tea may be helpful in fighting or preventing cancer. The inconclusive results of research studies does not mean that there is no link between green tea and cancer, as scientific studies often have to be redesigned and repeated in a variety of ways before meaningful information is generated. Numerous organizations around the world conduct studies looking at green tea, as well as other types of tea, with the goal of collecting more data.
Green tea has been consumed in Asia for centuries. It is made from the leaves of the Camellia sinensis plant and the leaves are very lightly processed. This makes green tea higher in antioxidants than other types of tea, such as black tea and oolong. Because antioxidants in general have been shown to be useful in preventing and fighting cancer, studies are based on whether the high number of antioxidants in green tea are beneficial as well.
Laboratory studies have shown that green tea can be selectively useful in inhibiting the growth of cancers, fighting tumors, and allowing organisms to live longer with cancers. However, when these studies are repeated in the human population, the evidence is less clear. There are a number of factors that are challenging to control for and can muddy results of scientific studies. In a simple example, studies looking at green tea and stomach cancer may ignore risk factors, such as a history of bacterial infections that tend to increase cancer risks, providing a poorly controlled sample and less applicable results.
Some studies on tea drinking populations have indicated that people who drink green tea are less likely to develop cancer, and more likely to live longer with cancer if cancer does occur. Other studies have not supported these findings on green tea and cancer. Large scale studies including exhaustive surveys of participants are necessary to identify other factors that may be influencing results, ranging from other dietary factors to environmental ones.
Studies on green tea and cancer certainly do not seem to suggest that green tea is harmful or increases the risk of cancer. People who choose to drink more green tea in case studies later support the use of green tea as a cancer preventative are unlikely to harm themselves, although it is advisable to combine tea drinking with other steps including eating a balanced diet, exercising, and remaining alert to cancer risk factors like environmental exposures.