The findings add to the evidence of an inverse relationship between coffee drinking and cancer of the large bowel.
While obesity, smoking and physical inactivity are established risk factors for colorectal cancer, nutritional factors in coffee also play an important role in the development of colorectal cancer.
Coffee contains antioxidant compounds that contribute to colorectal health and may explain its preventive properties via restriction of colon cancer cell growth.
Melanoidins generated during the coffee roasting process are thought to encourage colon mobility.
Diterpenes may inhibit cancer by enhancing the body’s defence against oxidative damage.
Researchers at the University of Southern California Norris Comprehensive Cancer Center began by looking at 5,100 men and women, who had been diagnosed with colorectal cancer within the past six months.
They also looked at 4,000 men and women with no history of colorectal cancer as the control group.
Subjects reported their daily consumption of boiled (espresso), instant, decaffeinated and filtered coffee, as well as their total consumption of other liquids.
A questionnaire gathered information about many other factors that influence the risk of colorectal cancer, including family history of cancer, diet, physical activity and smoking.
Results showed that even moderate coffee consumption, between one to two servings a day, was associated with a 26% reduction in the odds of developing colorectal cancer after adjusting for known risk factors.
In addition, the risk of developing colorectal cancer continued to decrease to up to 50% when participants drank more than 2.5 servings of coffee each day. The indication of decreased risk was seen across all types of coffee, both caffeinated and decaffeinated.
“We were somewhat surprised to see that caffeine did not seem to matter,” said Dr Stephen Gruber, director of the USC Norris Comprehensive Cancer Center and senior author of the study.
“This indicates that caffeine alone is not responsible for coffee’s protective properties.”
The mechanism of the possible protection of coffee against large bowel cancer is not well understood. It has been interpreted in terms of the antioxidant, antimutagenic and anticarcinogenic effects by coffee’s complicated compounds.
Coffee contains phenolic compounds such as chlorogenic, caffeic and cumaric acids, melanoidins and diterpenes (such as cafestol and kahweol), which have been confirmed to eliminate several carcinogens and reduce the oxidant effect of polycyclic aromatic hydrocarbons.
“The levels of beneficial compounds per serving of coffee vary depending on the bean, roast and brewing method,” said first author Dr Stephanie Schmit.
“The good news is that our data presents a decreased risk of colorectal cancer regardless of what flavour or form of coffee you prefer.”
Previous studies have identified a selection of lifestyle choices that participants who drank decaffeinated coffee practiced.
These individuals tended to consume less alcohol, fewer calories, and less red meat; eat more fruit and vegetables; exercise less; and smoke more than did participants who primarily drank caffeinated coffee.
One study also showed that people who regularly drank decaffeinated coffee were more health conscious in their behaviours than were people who did not.
Coffee in Europe
According to the European Coffee Federation, Europe has the highest per capita coffee consumption in the world.
The EU consumes 2.5 million tons coffee per year, which equates to four kilos of roasted coffee per EU inhabitant per year. Every day some 725 million cups of coffee are drunk in the EU.
Source: Cancer Epidemiology, Biomarkers & Prevention
Published online ahead of print, doi: 10.1158/1055-9965.EPI-15-0924
“Coffee Consumption and the Risk of Colorectal Cancer.”
Authors: Stephanie L. Schmit, Hedy S. Rennert, Gad Rennert, Stephen Gruber