Eating frequency and risk of colorectal cancer

Eating frequency is a modifiable aspect of dietary behavior that may affect risk of colorectal cancer (CRC). Although most previous case-control studies indicate a positive association, two prospective studies suggest an inverse association between eating frequency and CRC risk, with evidence of effect modification by diet composition. We examined the association between eating frequency and CRC in a large, prospective cohort study, and explored whether this relationship was modified by sex, coffee consumption, or dietary glycemic load. Between 2000 and 2002, 67,912 western Washington residents aged 50-76 reported average daily meal and snack frequency using a mailed questionnaire as part of the vitamins and lifestyle study. Participants were followed for CRC through linkage with SEER through 2008, over which time 409 CRC cases developed. Hazard Ratios and 95 % Confidence Intervals were obtained using Cox regression. In age- and sex-adjusted models higher (5+ times/d) vs. lower (1-2 times/d) eating frequency was associated with a HR of 0.62 (95 % CI 0.43-0.88, P-trend = 0.001). However, following further adjustment for BMI, race/ethnicity, alcohol, and other known CRC risk factors, the relationship was no longer statistically significant (HR: 0.76; 95 % CI 0.51, 1.14). No effect modification was observed by sex (P-interaction = 0.45), coffee consumption (P-interaction = 0.44), or dietary glycemic load (P-interaction = 0.90). In subgroup analyses by tumor site, higher vs. lower eating frequency was associated with lower risk for colon (HR 0.65 95 % CI 0.39-1.07, P-trend = 0.04), but not rectal cancers (HR = 1.08 95 % CI 0.54-2.18, P-trend = 0.94). The weak inverse association observed between eating frequency and CRC is consistent with findings from other prospective studies. Modification of this relationship by diet quality and participant characteristics should be considered in the future studies.