Index-based dietary patterns and colorectal cancer risk: a systematic review

Abstract

Colorectal cancer (CRC) is the third most common cancer in both men and women in the United States. Various a priori dietary patterns that take into account diet complexity have been associated with CRC risk. This systematic review augments the evidence for an association between CRC risk and the Mediterranean Diet Score (MDS) and the Healthy Eating Index (HEI), and provides new evidence for a novel Dietary Inflammatory Index (DII). Human studies published in English after 31 December 2008 were reviewed. Five case-control studies and 7 prospective cohort studies conducted in the United States and Europe were identified. Five of the studies examined the MDS, 4 examined the HEI, and 4 examined the DII. Comparing highest to lowest score groups, higher MDSs were associated with an 8-54% lower CRC risk, and higher HEI scores were associated with a 20-56% lower CRC risk. More proinflammatory diet scores were associated with a 12-65% higher CRC risk compared with more anti-inflammatory diets in studies that used the DII. The results reported by sex suggested similar associations for men and women. This review builds upon the evidence supporting the association between higher overall diet quality and lower risk of CRC. Increasing scores of MDS and HEI and anti-inflammatory DII scores are characterized by high intake of plant-based foods and low intake of animal products. Future studies in more diverse populations and with consistent scoring calculations are recommended.

Keywords: Dietary Inflammatory Index; Healthy Eating Index; Mediterranean diet; colorectal cancer; dietary patterns; epidemiology; systematic review.

FIGURE 1

PRISMA flow chart of the review process. PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses; CRC, colorectal cancer.

FIGURE 2

Forest plot of the associations between the MDS (A), HEI, and AHEI (B), and DII (C) and colorectal cancer risk in cohort and case-control studies stratified by sex (where available). *The studies in this figure were all stratified by sex except the study by Djuric et al. (17), which stratified analysis by high and low quercetin intake group. **The highest HEI index group was treated as referent group in the study by Jarvandi et al. (24), whereas the other studies in this figure used lowest HEI index group as the referent group. AHEI, Alternate Healthy Eating Index; aMed, alternate Mediterranean Diet index; CSMMDS, Center-Specific Modified Mediterranean Diet Score; DII, Dietary Inflammatory Index; HEI, Healthy Eating Index; MDS, Mediterranean Diet Score; MMDS, Modified Mediterranean Diet Score.