Patients with colon cancer whose diet consisted of more carbohydrates, including foods that cause high blood-sugar levels had an increased risk of cancer recurrence and death, a new study shows. According to the study authors, these findings support a role for dietary factors in colon cancer prognosis. Diet intervention may also be a way to improve patient survival. The results are published in the Journal of the National Cancer Institute.
Colon cancer patients who reported consuming a diet high in carbohydrates and foods that cause blood-sugar levels to quickly increase had lower disease-free survival, recurrence-free survival, and overall survival compared to those who reported a diet low in carbohydrates. The results were statistically significant.
The effect of a carbohydrate-rich diet varied according to a patient’s body mass index (P = .01). A high-carbohydrate diet did not affect the outcomes of patients of normal body weight, defined as a body mass index of 25 or less. But for cancer patients who were overweight or obese, a consistent consumption of foods that cause high blood-sugar levels resulted in worse disease-free survival (P < .001). Other factors such as age, sex, performance status of the patient, or physical activity level did not impact these results.
According to the lead author of the study, Jeffrey A. Meyerhardt, MD, of the Dana-Farber Cancer Institute, many patients seek recommendations on a diet they should follow after a colon cancer diagnosis. “In a previous study by our group, we reported that a higher Western pattern diet is associated with increased risk of colon cancer recurrence and mortality,” said Meyerhardt. The current study looked at components of the Western diet and “found that patients with diets higher in carbohydrates and foods that stimulate glucose and insulin in the body have a higher risk of recurrence,” said Meyerhardt.
The study was not a randomized study and further confirmation of the results will be needed. “It is a starting point to discuss with patients and consider in colon cancer survivors,” Meyerhardt pointed out. The prospective, observational study recruited 1,011 stage III colon cancer patients. The patients recorded their daily food intake during and after participation in an adjuvant chemotherapy clinical trial.
Compared with patients who consumed the lowest amount of carbohydrates, those patients who consumed the most had the highest risk of recurrence and death (hazard ratio = 1.8; P < .001). A higher glycemic load was similarly associated with the lowest disease-free survival (hazard ratio = 1.79; P < .001). Glycemic load estimates the food’s influence on a person’s glucose level after consumption.
Previous studies had found a direct link between hyperinsulinemia, a condition in which excess levels of insulin circulate in the blood, and colon cancer recurrence and death. The glycemic load of a food consumed affects insulin levels. One such study found that colon cancer patients who consumed the highest amounts of Western diet components such as meat, fat, and refined grains and sugars, had a three-fold increase in colon cancer recurrence compared to those patients who consumed the lowest amounts of these foods.
In the current study, Meyerhardt and colleagues examined the association of carbohydrates and sugar intake on colon cancer recurrence and survival.
Meyerhardt believes the current findings are related to increased insulin states that lead to tumor growth, similar to the effect of obesity and a lack of physical activity. “This mechanism is important in other cancer types like breast cancer but these results would need to be studied in those cancer types,” he said.
Is there enough evidence for oncologists to tell colorectal cancer patients to change their diets? In an editorial accompanying the study publication, Neal J. Meropol, MD, of the University Hospitals Case Medical Center in Cleveland, and Nathan A. Berger, MD, of the Comprehensive Cancer Center at Case Western in Cleveland, state that the current American Cancer Society panel guidelines on dietary recommendations should be followed—maintenance of a healthy weight, regular physical activity, and a well-balanced diet consistent with cancer and disease prevention guidelines.
“We have growing body of data that diet and lifestyle likely matter in colon cancer patients and should be discussed as potential considerations in their overall care,” said Meyerhardt. “All the patients in this cohort had surgery and adjuvant therapy for stage III disease, so this is not a substitute for standard treatment but a potential complementary therapy.”
Meyerhardt and colleagues are currently collecting more data on other colon cancer patients—those with early stage and metastatic disease to confirm the findings.