Drinking even large amounts of coffee and sugar-sweetened, carbonated soft drinks is not associated with the risk of colon cancer, according to a large study published online May 7 in the Journal of the National Cancer Institute.
Some previous studies have suggested that coffee and tea may lower the risk of cancer, but others show that they could increase the risk. Tea, for instance contains anti-oxidants that in theory help prevent cancer but also has polyamines, which in theory promote cancer. Sugar-sweetened soft drinks are associated with weight gain, obesity, and other conditions that are potential risk factors for colon cancer.
For this study, Xuehong Zhang, M.D., Sc.D., and colleagues at the Harvard School of Public Health analyzed data from 13 studies conducted in North America and Europe. Among 731,441 participants in these studies, there were 5,604 who developed colon cancer. Those who drank large amounts of coffee -- more than six 8-oz cups a day -- were no more likely to develop the disease than those who drank less.
Likewise, those who drank more than 18 oz daily of sugar-sweetened, carbonated beverages had no higher risk of colon cancer. But the authors note that the results for sugar-sweetened carbonated beverages should be interpreted with caution because only 2% of the study population drank more than 18 oz of these beverages daily.
The results were similar regardless of sex, smoking status, alcohol consumption, body mass index, level of physical activity, and location of the tumor.
The authors found a modest association between drinking high amounts of non-herbal tea -- more than four 8-oz cups a day -- and colon cancer risk. However, they note that very few people in the study drank that much tea and that the association could be due to chance.
"Drinking coffee or sugar-sweetened carbonated soft drinks was not associated with colon cancer risk," the researchers conclude. "However, a modest positive association with higher tea consumption is possible and requires further study."
In an accompanying editorial, Cynthia Thomson, Ph.D., and Maria Elena Martinez, Ph.D., of the Arizona Cancer Center, note that this study is a valuable contribution to the literature but that more research is needed on the links between childhood consumption of soft drinks and disease. "Contrary to coffee and tea consumption, intake of sweetened beverages begins in childhood in many countries," they write. "Furthermore, sweetened beverage consumption is generally much lower among older adults. These differences in exposure suggest that intake of sweetened beverages may need to be assessed earlier in life to adequately assess its association with health outcomes."
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