Influence of dietary insulin scores on survival in colorectal cancer patients

BACKGROUND: Although hyperinsulinemia is hypothesised to be involved in colorectal carcinogenesis, it remains unclear whether a diet inducing an elevated insulin response influences colorectal cancer (CRC) survival. METHODS: We examined the association of post-diagnosis dietary insulin scores with survival among 2006 patients from two large prospective cohorts who were diagnosed with CRC from 1976 to 2010. Dietary insulin load was calculated as a function of the food insulin index. Dietary insulin index was calculated by dividing insulin load by total energy intake. Cox proportional hazards models were used to calculate hazard ratios (HRs) for CRC-specific mortality and overall mortality, adjusted for other risk factors for cancer survival. RESULTS: The adjusted HRs for CRC-specific mortality comparing the highest to the lowest quintiles were 1.82 (95% CI: 1.20–2.75, P(trend)=0.006) for dietary insulin load and 1.66 (95% CI: 1.10–2.50, P(trend)=0.004) for dietary insulin index. We also observed an increased risk for overall mortality, with adjusted HRs of 1.33 (95% CI: 1.03–1.72, P(trend)=0.03) for dietary insulin load and 1.32 (95% CI: 1.02–1.71, P(trend)=0.02) for dietary insulin index, comparing extreme quintiles. The increase in CRC-specific mortality associated with higher dietary insulin scores was more apparent among patients with body mass index (BMI)⩾25 kg m(−2) than BMI<25 kg m(−2) (P(interaction)=0.01). CONCLUSIONS: Higher dietary insulin scores after CRC diagnosis were associated with a statistically significant increase in CRC-specific and overall mortality.