Proinflammatory Diet and Colorectal Cancer
Epidemiologic evidence suggests that a proinflammatory diet, as measured by the dietary inflammatory index, can increase the risk of developing CRC, particularly proximal colon cancer.
The Western diet — which includes a high intake of red meat, high-fat dairy products, refined grains, and simple carbohydrates — is associated with higher levels of inflammatory markers such as C-reactive protein and interleukin-6.1 Dietary patterns that include more whole grains, vegetables, and fish and lower red meat intake, such as the Mediterranean diet, are associated with lower levels of these inflammatory markers.
To study the effect of dietary pattern on inflammation-associated pathologies, the dietary inflammatory index (DII) was developed and validated. This tool assigns specific foods, beverages, and the constituents thereof a score, which indicates whether an individual's dietary intake is proinflammatory.
A high DII was significantly associated with overall cancer incidence (relative risk [RR], 1.25; 95% CI, 1.16-1.35), risk of developing cancer (odds ratio [OR], 1.75; 95% CI, 1.43-2.16), and cancer-related mortality (RR, 1.67; 95% CI, 1.13-2.48) compared with a low DII.2
Multiple studies have, furthermore, found an association between a high DII and the risk of colorectal cancer (CRC).
High DII and CRC
Compared with a low DII, a high DII is consistently associated with an increased risk of CRC in case-control and prospective cohort studies. A meta-analysis of 4 case-control and 4 prospective cohort studies that included 880,380 individuals demonstrated that a high DII was significantly associated with an increased risk of CRC (pooled adjusted RR, 1.43; 95% CI, 1.26-1.62).3
The association was significant among both men (RR, 1.51; 95% CI, 1.29-1.76) and women (RR, 1.25; 95% CI, 1.10-1.41). In a subgroup analysis, the association was most robust for colon cancer, though it was less so for rectal cancer. A prospective cohort study included in this meta-analysis evaluated anatomic sites and found that a high DII was associated with proximal colon cancer (HR, 1.35; 95% CI, 1.09-1.67), but not distal colon (HR, 0.84; 95% CI, 0.61-1.18) or rectal cancer (HR, 1.20; 95% CI, 0.84-1.72) in a multivariate analysis.4