Colon cancer patients who regularly drink caffeinated coffee may be lowering their risk of tumor recurrence and death from the disease, new research suggests.
But researchers added that it's premature to tell patients to drink coffee to reduce their risk of the cancer's return.
The study found that people with advanced (stage III) colon cancer who drank four or more cups of caffeinated coffee every day had 52 percent lower odds of disease recurrence or cancer death compared with coffee abstainers. Even people who regularly drank slightly less (two to three cups) per day appeared to reap some of the same benefits, just to a lesser degree.
"There is already an abundance of evidence that diet and lifestyle can have a great deal of positive impact in terms of reducing the risk for developing colon cancer," explained study lead author Dr. Charles Fuchs, director of the Gastrointestinal Cancer Center at the Dana-Farber Cancer Institute in Boston. "Now we have found that caffeinated coffee seems to independently improve the outcome for colon cancer patients," he said.
It's important to note, however, that this study was only designed to find an association between coffee consumption and a lower risk of colon cancer recurrence or death from colon cancer. It wasn't designed to prove a cause-and-effect relationship.
The study findings were released online Aug. 17 in the Journal of Clinical Oncology.
To explore coffee's impact on colon cancer, the research team focused on roughly 950 people with stage III colon cancer. They all completed nutrition questionnaires while undergoing postsurgical chemotherapy treatment at some point between 1999 and 2001.
Dietary information was collected again six months after completion of chemotherapy.
The study volunteers were asked about more than 130 different food and drink items. Those items included caffeinated coffee, decaffeinated coffee and non-herbal (caffeinated) tea. In turn, cancer recurrence and patient death rates were followed for an average of a little more than seven years.
Cancer returned in 329 people, mostly within five years of initial treatment, the study found. Of these, 288 died of their disease. An additional 36 people who didn't have a diagnosis of a cancer recurrence also died during the study follow-up.
The researchers found that drinking two cups of caffeinated coffee daily was associated with a reduced risk for cancer recurrence and colon cancer death. That protection was even greater for those consuming three or four cups of coffee daily. The findings held up even after accounting for other foods that might impact disease progression, such as sugar-sweetened beverages and carbohydrates.
However, consuming non-herbal tea, decaf coffee or just a single cup of coffee a day was not linked to any protective benefit, the investigators found.
So is caffeine the magic bullet?
"For one, we really had too few patients drinking decaf coffee or non-herbal tea to really say what their specific impact might be," acknowledged Fuchs. "And it is also true that coffee has a lot of components in addition to caffeine that could possibly be relevant to colon cancer," he added.
"But I do think it would be reasonable to conclude that it could be the caffeine in coffee that is affecting the colon cancer pathway," Fuchs said. "It's just that for now we can't say for sure. We need to confirm these findings in other patient populations."
But, Fuchs said he wouldn't promote coffee to patients who aren't already fans.
"If patients are already drinking coffee regularly I would certainly say go ahead and continue to do so," he said. "But we need to look at this some more. And meanwhile, there are plenty of healthy lifestyle choices that can help, including avoiding obesity, avoiding a high-carb diet, and avoiding sugary beverages, to name a few."
That advice was seconded by Dr. Andrew Chan, an associate professor in the department of medicine at Harvard Medical School, and an associate professor of medicine in the department of gastroenterology at Massachusetts General Hospital in Boston.
"I think to some extent telling patients to go start drinking coffee would be a premature recommendation," Chan said.
"Yes, this was a carefully done study that does suggest that coffee certainly isn't harmful, and there's certainly some value for patients. But I'm not sure that the apparent benefit of coffee is clear enough yet to warrant any clinical recommendations. That will require additional research to establish direct causality," Chan added.