Harvard study finds no coffee, soda link to colon cancer

Writing in the Journal of the National Cancer Institute​, the researchers sought to examine the evidence behind suggestions that high tea, coffee, and soft drink consumption could be associated with colon cancer.

Concern about a link is based on the fact that sugar-sweetened soft drinks are associated with weight gain and obesity, conditions that are potential risk factors for colon cancer.

To establish whether a link does indeed exist between such drinks and colon cancer, Xuehong Zhang and colleagues at the Harvard School of Public Health analysed data from 13 prospective cohort studies in North America and Europe. These involved 731,441 participants, 5,604 of whom developed colon cancer.

Study results​

Examining this data, the scientists found that those who drink more than six 8-oz cups of coffee a day or 18 oz daily of sugar-sweetened carbonated drinks were no more likely to develop colon cancer. Meanwhile, a modest association was uncovered between drinking more than four 8-oz cups a day of non-herbal tea and colon cancer risk.

The results were similar regardless of sex, smoking status, alcohol consumption, body mass index, physical activity, and tumor site.

Limitations ​

However, the scientists did flag up some caveats to the findings. The data on coffee was limited to a European population and only 2 per cent of the population considered in the study consumed the previously defined high amounts of tea and soft drinks.

The authors therefore said the study “may be underpowered to draw conclusions for high consumption levels”. ​

Editorial ​

Nevertheless, Cynthia Thomson and María Elena Martínez from the Arizona Cancer Center at the University of Arizona said in an editorial on the study in the J Natl Cancer that the results “contribute valuable information, given the paucity of literature in this area.”​ But the scientists called for further research to confirm the findings and to explore the impact of long term consumption habits.

They even suggested that the failure to find any link could be explained by the sheer breadth of the data examined. “It could be hypothesized that null results based on these studies are the result of countering carcinogenesis influences leading to a net overall null association or that weak associations are attenuated because of measurement error.”​

To read their comments in full, click here.​

Source: The Journal of the National Cancer Institute
J Natl Cancer Inst 2010;102(11)
Risk of Colon Cancer and Coffee, Tea, and Sugar-Sweetened Soft Drink Intake: Pooled Analysis of Prospective Cohort Studies
Authors: Xuehong Zhang et al.

Coffee, Tea, What Beverage for Me? Associations Between Beverage Intake and Colorectal Neoplasia Risk
Authors: Cynthia A. Thomson and María Elena Martínez