Parts of Mediterranean Diet Linked With Reduced Colon Polyp Risk

Adherence to a Mediterranean diet is negatively associated with advanced colorectal polyps, and the specific portions of the diet that appear to have the most influence include high intake of fish and fruit and low intake of soft drinks, according to a new study.

Previous research has shown that a Mediterranean diet can offer colorectal protection, but the specific elements involved were unknown. Naomi Fliss Isakov, PhD, of Tel Aviv Medical Center in Israel, presented results of the new study at the European Society for Medical Oncology (ESMO) 19th World Congress on Gastrointestinal Cancer, held June 28-July 1 in Barcelona, Spain (abstract #O-023).

The new research was a case-control study of 808 individuals aged between 40 and 70 years who underwent screening or diagnostic colonoscopy. Patients also participated in a medical and lifestyle interview, and completed a detailed food frequency questionnaire. The Mediterranean diet was considered to include vegetables and legumes, fruits, nuts and seeds, whole grains, fish, a ratio of monounsaturated fats to saturated fatty acids and poultry above the sample median, and consumption of red meat, alcohol, and soft drinks below the sample median.

Patients with advanced colorectal polyps adhered to fewer components of the diet than control patients with no polyps, at a mean of 4.5 components compared to 5.1 components (P = .03). The mean number of adhered components was significantly associated with lower odds of advanced polyps on a multivariate analysis, with an odds ratio (OR) of 0.81 (95% CI, 0.73–0.90).

Adherence to 1 to 4 components of the Mediterranean diet yielded an OR of 0.50 (95% CI, 0.32–0.79; P = .003) compared to adherence to none. Adherence to 5 to 10 components yielded an OR of 0.47 (95% CI, 0.26–0.83; P = .009), again compared to adherence to none.

The researchers then analyzed which specific components were negatively associated with advanced polyps, after adjustment for potential confounders and to all other dietary components. The only components that were significantly associated included low intake of soft drinks, with an OR of 0.65 (95% CI, 0.44–0.97); high intake of fruit, with an OR of 0.66 (95% CI, 0.45–0.95); and high intake of fish, with an OR of 0.62 (95% CI, 0.42–0.91). Adherence to all three of these dietary components yielded an OR for advanced polyps of 0.14 (95% CI, 0.04–0.41).

Isakov said the next step in this research is to test whether the Mediterranean diet retains a protective effect even among groups at high risk for colorectal cancer, according to a press release.

ESMO spokesperson, Dirk Arnold, MD, PhD, of Instituto CUF de Oncologia in Lisbon, Portugal, commented on the study, and said that this does confirm the associations seen between diet and colorectal risk. “However, it remains to be seen whether these results are associated with reduced mortality, and it is also unclear if and when a dietary change would be beneficial,” he said. “Despite this lack of information, it makes sense to consider this diet for other health-related reasons also.”