Many studies have pointed to coffee’s health benefits, suggesting coffee may protect against Type 2 diabetes, reduce overall deaths and perhaps even help protect against dementia.

Colon cancer patients who were heavy coffee drinkers had a far lower risk of dying or having their cancer return than those who did not drink coffee, with significant benefits starting at two to three cups a day, a new study found. Patients who drank four cups of caffeinated coffee or more a day had half the rate of recurrence or death than non-coffee drinkers.

But, the researchers caution, cancer patients should not start ordering extra tall coffees. The study, the first to report such findings, does not prove a cause-and-effect relationship between coffee drinking and a lower risk of colon cancer recurrence. As other experts note, there may be differences between heavy coffee drinkers and abstainers that the research was not able to account for.

In recent years, many studies have pointed to coffee’s health benefits, suggesting coffee may protect against Type 2 diabetes, reduce overall deaths and perhaps even help protect against dementia. Other studies have suggested coffee may reduce the risks of certain cancers, including colon cancer. The benefits are generally attributed to coffee’s antioxidant and anti-inflammatory properties.

But as with many studies about diet, proving a link between coffee consumption and protection against cancer recurrence is difficult.

“Think about it: People who drink a lot of coffee tend to be highly stress, highly pressured, intense and compulsive,” said Dr Alfred Neugut, a professor of cancer research, medicine and epidemiology at Columbia University and a director of New York-Presbyterian Hospital’s Cancer Prevention Center. “If they have cancer, they’re going to be more obsessive about following all the rules and doing all the things they’re supposed to do. So it may be that coffee itself is playing a physiological role, but it may also be a surrogate marker for you being a compulsive health-conscious good behaviour.”

Dr Charles S Fuchs, the director of the Gastrointestinal Cancer Center at Dana-Farber Cancer Institute in Boston, who led the research, acknowledged the limitations of his study and called for interventional studies to replicate and confirm the findings.

“No one has ever done this before in colon cancer patients. It does require confirmation,” he said. 

Patients should not start drinking coffee based on this study, but, “If you’re a coffee drinker and enjoy your coffee, stick with it,” he said.   

“If a patient says, ‘Well I hate coffee,’ I’d say there are other things you can do, like avoid obesity, exercise regularly and follow a balanced diet.” 

The study, published in The Journal of Clinical Oncology, followed 953 patients with Stage 3 colon cancer who had been treated with surgery and chemotherapy.

The patients, recruited from 1999 to 2001, were asked to fill out detailed dietary pattern questionnaires about food intake and lifestyle, first during chemotherapy and again six months later. The questionnaires asked about their intake of caffeinated or decaffeinated coffee, herbal and nonherbal tea, caffeinated soft drinks and chocolate.

The researchers adjusted the findings to control for differences such as gender, age, smoking, diet, caloric intake, consumption of sugar-sweetened beverages and alcohol, weight and physical activity. They did not, however, adjust for use of aspirin and other nonsteroidal anti-inflammatory drugs, even though their earlier work suggests such drugs may be protective against colon cancer recurrence. Dr Fuchs said their previous research had not shown any association between coffee drinking and aspirin use.

They determined that patients who had reported drinking four or more cups of affeinated coffee a day were 52 percent less likely to have had a recurrence of cancer or to have died than those who had never drank coffee, while those who drank two to three cups of caffeinated coffee a day were 31 percent less likely than nondrinkers to have had a recurrence or to have died. Sweetened coffee beverages did not count.

The researchers’ hypothesis is that the factors that increase risk for Type 2 diabetes, such as obesity, a sedentary lifestyle and high insulin levels, also drive colon cancer, Dr Fuchs said. And many studies have shown that coffee consumption is associated with a lower risk for Type 2 diabetes, a chronic illness that may increase the risk of colon cancer. “We believe that activating the energy pathways that contribute to heart disease and diabetes is also relevant for the proliferation of cancer cells,” Dr Fuchs said, while also stressing that more research was needed.

The analysis determined the lowered risk associated with coffee was entirely because of the caffeine. One hypothesis is that caffeine increases the body’s sensitivity to insulin, so it requires less of the hormone. That, inturn, may reduce inflammation, which is a risk factor for diabetes and cancer. While there are inevitably gaps in these kinds of studies, the new research is “one piece of a big puzzle,” said Dr Len Lichtenfeld, the deputy chief medical officer at the American Cancer Society, adding that there is tremendous concern about the role obesity and metabolic factors may play in promoting cancer.

“This is an example of trying to look at those types of questions—about what the metabolic relationships are, and what might influence those metabolic relationships—in a positive way.”