Drinking more than 2.5 servings of coffee daily reduced the risk of colorectal cancer by up to 50% in the new study.
Senior study author Dr. Stephen Gruber, of the University of Southern California (USC) Norris Comprehensive Cancer Center, and colleagues publish their findings in the journal Cancer Epidemiology, Biomarkers & Prevention.
In the US, colorectal cancer is the second most common cancer among men and women combined, excluding skin cancer, with more than 95,000 new cases of colon cancer and 39,000 new cases of rectal cancer expected to be diagnosed this year.
The American Cancer Society state that the lifetime risk of developing colorectal cancer is 1 in 21 for men and 1 in 23 for women.
But according to this latest research, one of America's favorite beverages - coffee - could have a protective effect against the disease.
Colorectal cancer risk halved with more than 2.5 coffee servings daily
For their study, Dr. Gruber and colleagues analyzed the data of 5,145 individuals who had been diagnosed with colorectal cancer, alongside 4,097 people who did not have the disease.
All participants were part of the Molecular Epidemiology of Colorectal Cancer (MECC) study, which is a population-based, case-control study conducted in northern Israel.
- Around 54% of American adults drink coffee every day
- 65% of Americans drink their coffee with breakfast
- The US spends around $40 billion on coffee each year.
As part of the study, subjects were required to complete a food frequency questionnaire, detailing their daily intake of espresso, instant, decaffeinated and filter coffee, as well as their daily consumption of other beverages.
The participants also completed a questionnaire that disclosed information on family history of cancer, diet, physical activity levels, smoking habits and other factors that may affect their risk of colorectal cancer.
The researchers found that drinking one to two servings of coffee a day - defined as moderate coffee consumption - reduced the risk of colorectal cancer by 26%, compared with participants who drank less coffee.
And the risk reduced even further with an increase in coffee intake; participants who consumed more than 2.5 servings of coffee daily had up to a 50% lower risk of colorectal cancer.
Not only did these findings remain after accounting for known colorectal cancer risk factors, but the researchers also found that the reduced risk was seen across all coffee types - even decaffeinated.
"We were somewhat surprised to see that caffeine did not seem to matter," says Dr. Gruber. "This indicates that caffeine alone is not responsible for coffee's protective properties."
What other coffee compounds are at play?
If caffeine is not solely responsible for coffee's protective effect against colorectal cancer, what is?
The researchers explain that both caffeine and polyphenol have antioxidant properties that can reduce the growth of colon cancer cells.
Additionally, studies have suggested that compounds called melanoidins - which are produced during the roasting process - boost colon mobility, while the compound diterpene in coffee may boost the body's defense against oxidative damage, preventing cancer development.
"The levels of beneficial compounds per serving of coffee vary depending on the bean, roast and brewing method," says first author Stephanie Schmit, PhD, also of the USC Norris Comprehensive Cancer Center. "The good news is that our data presents a decreased risk of colorectal cancer regardless of what flavor or form of coffee you prefer."
The researchers note that in Israel - where the study participants were from - coffee consumption is less common and more variable than in the US.
However, because their results indicate the protective effect of coffee exists across all types, the researchers believe there is no reason to believe the findings would not be applicable to Americans.
Still, Dr. Gruber says further research is needed before they can recommend coffee consumption as a preventive strategy for colorectal cancer. He adds:
"That being said, there are few health risks to coffee consumption, I would encourage coffee lovers to revel in the strong possibility that their daily mug may lower their risk of colorectal cancer."
Coffee consumption has been linked to an array of possible health benefits. In February, Medical News Today reported on a study suggesting that coffee protects against liver cirrhosis, while a more recent study suggests six cups of coffee daily may lower the risk of multiple sclerosis (MS).
However, some studies have noted the possible health risks of coffee consumption. A study published last September, for example, found that drinking coffee in the evening may disrupt our body clock.