Evidence supports a role of whole grains in colorectal cancer (CRC) prevention, but the association between gluten intake and CRC risk in healthy populations is unclear. We examined the association of grain and gluten intake with risk of CRC overall and by subsite among Cancer Prevention Study-II Nutrition Cohort participants.
In 1999, 50,118 men and 62,031 women completed food frequency questionnaires assessing grain intake. Gluten intake was estimated using the protein content of grain products. Multivariable-adjusted hazards ratio (HR) and 95% confidence interval (CI) of CRC risk were estimated using Cox proportional hazards regression.
During follow-up through 2013, 1742 verified CRC cases occurred. For the highest vs. lowest quintiles of whole grain intake, HRs (95% CIs) of CRC risk were 0.77 (0.61-0.97; P trend = 0.03) among men and 1.10 (95% CI 0.88-1.36; P trend = 0.14) among women (P interaction by sex = 0.01). Men in the highest vs. lowest quintile of whole grain intake had a 43% lower risk of rectal cancer (HR = 0.57, 95% CI 0.35-0.93, P trend = 0.04). Gluten intake was not associated with CRC risk overall (HR = 1.10, 95% CI 0.93-1.32, P trend = 0.10), but was associated with risk of proximal colon cancer among men and women, combined (HR = 1.37, 95% CI 1.07-1.75, quintile 5 vs. 1, P trend = 0.001) and separately. Refined grains and grain-based sweets were not associated with CRC risk.
We found that higher whole grain intake was associated with lower CRC risk among older US men, but not women. The positive association of gluten intake with the risk of proximal colon cancer deserves further study.