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 online Feb. 16 in JAMA Network Open.
Sajesh K. Veettil, Ph.D., from University of Utah in Salt Lake City, and colleagues assessed the quality of evidence in meta-analyses of prospective observational studies evaluating the association between dietary factors and the incidence of CRC.
The researchers identified 45 meta-analyses 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 meta-analysis models. There was large heterogeneity between studies for 17 associations (15.6 percent), while small-study effects were found for 11 associations (10.1 percent). 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 percent) of the associations. Convincing evidence supported associations of intake of red meat (high versus low) and alcohol (four or more drinks/day versus zero 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.
“More research is needed on specific foods for which evidence remains suggestive, including other dairy products, whole grains, processed meat, and specific dietary patterns,” the authors write.