New research led by Dana-Farber Cancer Institute investigators suggests that patients treated for non-metastatic colon cancer may sharply reduce the risk that the disease will return by following a diet low in carbohydrates and other foods that raise insulin levels.
In a study published in the Journal of the National Cancer Institute, researchers found that patients with stage III colon cancer who had the highest "dietary insulin load" – the level of insulin produced by the body in response to diet – were twice as likely to have a recurrence or die of the disease than patients with the lowest load. The trend held regardless of level of physical activity and was especially strong in patients who were obese, the researchers found.
"These research results should be empowering to this group of patients," says the study's lead author, Vicente Morales-Oyarvide, MD, MPH, of Dana-Farber. "We now have evidence that they may help avoid a recurrence of the disease and improve their prospects of survival by following a healthy diet."
Previous studies have indicated that colon cancer survivors who have a healthy lifestyle – who are physically active, control their weight, and avoid a Western-pattern diet – have a better prognosis than those with less-healthy habits. Scientists have proposed that this benefit is partly due to the lower levels of insulin induced by these healthy behaviors. Morales-Oyarvide and his colleagues sought evidence of such a connection.
The study enrolled 1,023 patients who had undergone surgery for colon cancer and were participating in a clinical trial of follow-up chemotherapy. Halfway through their chemotherapy treatment, and six months after completing therapy, they filled out a questionnaire about their dietary intake, enabling researchers to calculate each patient's dietary insulin load.
Diets high in simple carbohydrates (such as white bread and refined-grain pastas), sugar, and fat – prominent components of Western-pattern diets – tend to produce high insulin levels. Mediterranean-style diets, which are rich in vegetables, fruits, legumes, and healthy fats and proteins, are associated with lower insulin levels. The advantage of looking at overall dietary insulin load in this study is that it accounts not only for carbohydrate consumption, but fat and protein consumption as well, Morales-Oyarvide states.
The finding that patients with the highest dietary insulin load had twice the risk of colon cancer recurrence and death as those with the lowest load underscores the role patients themselves can play in helping to reduce their risk, says Dana-Farber's, Kimmie Ng, MD, MPH, the study's senior author.
"Patients are always interested in what they can do to reduce their risk of cancer recurrence," Ng remarks. "We now have dietary advice that, our research shows, may make a difference."
The co-authors of the study are: Chen Yuan, ScD, Ana Babic, PhD, Sui Zhang, MS, Robert J. Mayer, MD, Brian M. Wolpin, MD, and Jeffrey A. Meyerhardt, MD, of Dana-Farber; Shuji Ogino, MD, PhD, of Dana-Farber, Brigham and Women's Hospital, and Harvard T.H. Chan School of Public Health; Donna Niedzwiecki, PhD, and Xing Ye, of Duke University; Jennie C. Brand-Miller, PhD, of the University of Sydney, Sydney, Australia; Laura Sampson-Kent, MS, Yanping Li, MD, PhD, Kana Wu, MD, PhD, and Walter C. Willet, MD, MPH, DrPH, of Harvard T.H. Chan School of Public Health; Edward L. Giovannucci, MD, ScD, of Harvard T.H. Chan School of Public Health and Brigham and Women's Hospital; Leonard B. Saltz, MD, of Memorial Sloan Kettering Cancer Center; Rex B. Mowat, MD, of Toledo Community Hospital; Renaud Whittom, MD, of Hôpital du Sacré-Coeur de Montréal, Montreal, Canada; Alexander Hantel, MD, of Loyola University Stritch School of Medicine; Al Benson, MD, of Robert H. Lurie Comprehensive Cancer Center, Northwestern University; Daniel Atienza, MD, of Virginia Oncology Associates; Michael Messino, MD, of Southeast Clinical Oncology Research Consortium, Mission Hospitals, Asheville, N.C.; Hedy Kindler, MD, of University of Chicago Comprehensive Cancer Center; Alan Venook, MD, of University of California at San Francisco Comprehensive Cancer Center; and Charles S. Fuchs, MD, MPH, of Yale Cancer Center.
The study was supported by the National Cancer Institute of the National Institutes of Health [grants U10CA032291, U10CA041287, U10CA045808, U10CA077651, U10CA138561, U10CA180791, U10CA180836, U10CA180867, U10CA180821, U10CA180882, R35CA197735, R01CA118553, R01CA169141, P50CA127003, R01CA149222, K07CA148894, and R01CA205406]; the Project P Fund; and Stand Up to Cancer.