Clinical studies examining the effect of green tea consumption on colon cancer produced compelling yet contradictory results. Several studies suggest that the anti-oxidant ingredients in green tea can help prevent the onset of colon cancer. Other studies are less conclusive, leaving some scientists unconvinced that there is a direct correlation.
History
Green tea is a traditional beverage in many cultures of Asia. People in Japan, China and India have consumed green tea for many centuries. According to the University of Maryland Medical Center, green tea is thought to have medicinal properties in these countries. It is credited with strengthening the heart, improving the digestive tract and sharpening the mind.
Ingredients
Green tea contains unfermented leaves from the Camellia sinensis plant. Oolong tea and black tea contain the same leaves but are fermented. Fermenting tea leaves removes polyphenols. According to the University of Massachusetts Lowell, polyphenols give green tea its cancer protecting qualities. Oolong tea and black tea also contain polyphenols, but not as much as green tea.
Population-Based Studies
Studies on green tea based on population suggest that the anti-oxidant properties contribute to a lower incidence of colon cancer. University of Maryland scientists say this is based on the fact that countries in Asia where green tea is commonly consumed have relatively low rates of colon cancer. However, these types of studies cannot conclusively state that green tea is the only reason for the low incidence of colon cancer.
Clinical Studies
According to the University of Cincinnati and Ohio State University, several clinical studies produced convincing data that catechins and polyphenols in green tea can inhibit colon cancer. One study found that women drinking at least five cups of green tea every day significantly lowered their colon cancer risk compared to women who did not drink green tea.
Inconsistencies
Many of the clinical studies that showed lower colon cancer risk in women who drink green tea showed no such effect for men who drink green tea. Others studies show no effect on green tea drinkers at all. University of Maryland researchers say more study is needed before green tea can be definitively linked to colon cancer prevention.
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