No link between coffee, fizzy drinks and bowel cancer, says large US study

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Scientists at the Harvard School of Public Health analysed data from 13 previous studies which had been carried out in the US and Europe.

A total of 731,441 people were followed for a number of years, 5,604 of whom developed bowel cancer during that time.

The latest analysis revealed that people who drank more than six cups of coffee per day were no more likely to develop bowel cancer than those who drank less or none at all.

People who drank more than 532ml (about one and a half cans) of sugary fizzy drinks each day also had no increased risk of the disease - although the scientists noted that just two per cent of participants had consumed this volume of fizzy drinks.

For tea, the scientists found a modest association between drinking more than four cups per day and bowel cancer risk.

Again, however, few people in the study had consumed these volumes of tea, making it hard to draw a reliable conclusion.

Writing in the Journal of the National Cancer Institute, the researchers concluded that drinking coffee or sugary fizzy drinks "was not associated with colon cancer risk".

"However, a modest positive association with higher tea consumption is possible and requires further study," they added.

Drs Cynthia Thomson and Maria Elena Martinez, from the Arizona Cancer Centre, said that more research is needed to determine the effect of drinking soft drinks during childhood on bowel cancer risk.

Writing in an accompanying editorial, they noted that many children start drinking fizzy drinks at an early age.

"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," they observed.

Yinka Ebo, health information officer at Cancer Research UK, said: “This study adds to the evidence that coffee is unlikely to have an effect on cancer risk, although the story for tea is less clear. While sugary fizzy drinks didn’t increase cancer risk directly, they can be high in calories, so drinking too many can lead to weight gain.

“Research shows that people who are overweight or obese have a higher risk of cancer. The best way to reduce bowel cancer risk is to eat more fibre and less red or processed meat, keep a healthy weight and be regularly active.”

Reference

1. Zhang X, Albanes D, et al. Risk of colon cancer and coffee, tea, and sugar-sweetened soft drink intake: pooled analysis of prospective cohort studies. Journal of the National Cancer Institute 2020. doi: 10.1093/jnci/djq107
2. Thomson CA, Martínez ME. Coffee, tea, what beverage for me? Associations between beverage intake and colorectal neoplasia risk. Journal of the National Cancer Institute 2010. doi: 10.1093/jnci/djq158

klíčová slova: fizzy drinks, coffee, bowel cancer