A pilot study of a low glycemic load diet in patients with stage I-III colorectal cancer

Consumption of a diet with high glycemic indices has been associated with inferior cancer-specific outcomes in patients with early-stage colorectal cancer, but there is limited prospective evidence that alterations in dietary habits improves cancer outcomes. This study aimed to determine the feasibility and acceptability of following a low glycemic load (GL) diet in patients with stage I-III colorectal cancer.

Patients with stage I-III colorectal cancer, who completed definitive therapy, and consumed an average daily GL >150 participated in a 12-week tailored face-to-face dietary intervention with a target GL. This study followed a 2-stage design, with 4 planned cohorts, each with an assigned GL target and dietary intervention intensity. The primary endpoint of feasibility was determined by participant compliance, defined as an individual following the assigned GL ≥75% of the time. Compliance was determined using 24-hour telephone recalls. A cohort was deemed feasible if at least 67% of participants were compliant. Secondary endpoints included acceptability of the diet, nutritional support resources necessary to follow the diet, and evaluation of the effect of the diet on physical measures and correlative laboratories.

Only cohort 1 was required as the primary endpoint of feasibility was met (stringent GL target, low intensity dietary support). The majority of participants experienced a decrease in body mass index (BMI) and waist circumference, 29% experiencing meaningful weight loss (≥5%). The dietitian spent an average of 6.97 hours (SD 2.18) face-to-face time and 1.58 hours (SD 0.68) by phone with each participant. Significant decreases were seen in total cholesterol, very-low-density lipoprotein (VLDL) and triglycerides (all P<0.05). All participants liked the foods and were satisfied with the diet. All participants felt the in-person meetings were helpful, and 62% did not feel a virtual meeting (e.g., Skype, etc.) could replace in-person meetings.

Patients with stage I-III colorectal cancer can follow a low GL diet with a 12-week in-person dietary intervention. Significant changes in physical and laboratory measures suggest relevant biologic effects of the dietary intervention. This study establishes feasibility, and warrants a larger scale prospective intervention trial to evaluate the impact of a low GL diet on cancer outcomes.