Coffee Consumption Not Linked to Colon Cancer; Actual Effect Still Unclear

Coffee Consumption Not Linked to Colon Cancer

Studies about coffee and cancer come out fairly regularly and this new one about coffee consumption and colon cancer is no exception. The good news is that the findings are consistent with past research that shows coffee may be able to reduce one’s risk of colon cancer. The bad news is that it suffers from some of the same limitations as past investigations and this restricts how informative it can be. The study is from the University of Southern Carolina and is published in the April 1, 2016, issue of Cancer Epidemiology, Biomarkers & Prevention.

The Coffee Cancer Study: Summary

  • 5,145 Israeli men and women who had been diagnosed with colorectal cancer in the past six months were asked about their coffee drinking habits including type, quantity, and other drinks they imbibed.
  • 4,097 men and women with no history of colorectal cancer were asked as well and served as the control group.
  • Questions were also asked about other colorectal cancer risk factors and the data analysis made sure to rule out their influence.
  • Coffee consumption (one to two servings per day) was associated with a 26% lower likelihood of developing colorectal cancer, with higher rates of consumption (over two and a half servings per day) showing stronger effects, reaching as high as 50%.
  • The effects are suspected to be due to certain antioxidants coffee contains or other chemicals that can promote colon activity.

Caveats

It’s worth pointing out that this study suffers from two very distinct limitations. The first is that it isn’t possible to establish when exactly the cancer group’s diseases developed or what their coffee habits were beforehand. This means that it’s very possible that the coffee habits the cancer patients reported in the study are different from how they actually drank before their cancer appeared—the period that actually matters for risk calculation. Since colon cancer affects digestion and eating habits, it’s possible that at least some of the cancer group may have previously been heavy coffee drinkers but had to scale back in response to the cancer symptoms. This makes it harder to determine how much the protective effect correlates to actual servings of coffee and could lead to the benefit seeming larger than it actually is, if one exists.

The second limitation is that this study is looking at people who were already diagnosed with cancer. In other words, the study is not looking at how drinking coffee affects someone’s chance of developing colon cancer; it’s looking at how many people with colon cancer drink coffee versus people with no cancer.

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This distinction is important because, if more people in the non-cancer group wore the color red, it could be concluded through the same reasoning that wearing red has a protective effect. To be fair, coffee has a much higher biological plausibility and body of research to support having protective properties against colon cancer, but the point remains that gathering data in this way is more prone to false positives.

Although the focus on an entirely Israeli population is unique, the findings themselves are consistent with past research into coffee and colon cancer. Previous studies have found associations of various strengths between drinking coffee and reduced incidences of colon cancer, though the observed potency of the protection tends to differ depending on the study in question.

Unfortunately, not much more can be said. As even the study’s author says, more specific research is needed to know anything more about this phenomenon and it would be premature to advocate coffee drinking as a preventative measure. More controlled studies that look at the suspected chemicals in particular instead of coffee as a whole, for instance, would provide a clearer understanding of how this works.

Bottom Line

  • The study shows a possible protective effect between coffee drinking and colon cancer, but the way the data was collected makes it more prone to false positives and could inadvertently make the effect seem larger than it actually is.
  • The findings are in line with past research into coffee and colon cancer and this supports the idea that a protective effect does exist.
  • These findings, even when combined with past research, are not specific or consistent enough to recommend any action on part of the public or those at risk of colon cancer.
  • Much more specific research is needed to know what is behind the purported protective effect.

Sources:
Schmit, S., et al., “Coffee Consumption and the Risk of Colorectal Cancer,” Cancer Epidemiology, Biomarkers & Prevention, 2016; doi:10.1158/1055-9965.EPI-15-0924.
“New study links coffee consumption to decreased risk of colorectal cancer,” Eureka Alert web site, April 1, 2016; http://www.eurekalert.org/pub_releases/2016-04/uosc-nsl033016.php, last accessed April 1, 2016.
“Coffee consumption and cancers of the digestive tract,” Coffee & Health web site; http://coffeeandhealth.org/topic-overview/coffee-consumption-and-cancers-of-the-digestive-tract/, last accessed April 1, 2016.

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