Higher intakes of dietary fiber, dietary calcium, and yogurt and lower intakes of red meat and alcohol are associated with a lower risk for colorectal cancer (CRC), according to a review published in JAMA Network Open. Researchers assessed the quality of evidence in meta-analyses of prospective observational studies evaluating the association between dietary factors and the incidence of CRC. They identified 45 metaanalyses that described 109 associations between dietary factors and CRC. Nearly one-third of the associations (35 of 109) were nominally statistically significant using random-effects metaanalysis models. There was large heterogeneity between studies for 17 associations (15.6%), while small-study effects were found for 11 associations (10.1%). There was no excess significance bias noted for any association between diet and CRC. For associations between diet and CRC, a primary analysis identified five as convincing, two as highly suggestive, 10 as suggestive, and 18 as weak. There was no evidence for 74 (67.9%) of the associations. Convincing evidence supported associations of intake of red meat (high versus low) and alcohol (≥4 drinks/day vs 0 or occasional drinks) with CRC incidence, and inverse associations of higher versus lower intakes of dietary fiber, dietary calcium, and yogurt with CRC risk. These convincing associations remained robust in sensitivity analyses.
