The association between pro-vegetarian dietary pattern and risk of colorectal cancer: a matched case-control study

BACKGROUND: Few studies assess the link between plant-based diets and colorectal cancer (CRC) incidence. To our knowledge, no study has examined the association between pro-vegetarian dietary pattern (PDP) and CRC globally or among Iranians. Therefore, the objective of our matched case-control study was to evaluate the association between PDP and CRC in the Iranian population. METHODS: The present research was a hospital-based case (n = 71)-control (n = 142) study conducted in the same hospitals in Tehran, Iran. This study used a reliable and valid semi-quantitative food frequency questionnaire to evaluate the participants’ dietary intake. According to the residual method, the selected plant and animal foods have been adjusted in the total energy intake to calculate the PDP index. Odds ratios (ORs) and 95% confidence intervals (CIs) adjusted for confounding variables were also expressed using logistic regression by SPSS software. RESULTS: In the crude and adjusted models, we observed that the odds of CRC decreased significantly in the 3rd and last quartile of PDP compared to the 1st quartile (Q) (Crude model: Q(3): OR = 0.36, 95% CI: 0.17 − 0.79, P-value = 0.011 and Q(4): OR = 0.33, 95% CI: 0.14 − 0.79, P-value = 0.012 - Adjusted model: Q(3): OR = 0.41, 95% CI: 0.18 − 0.94, P-value = 0.035 and Q(4): OR = 0.35, 95% CI: 0.14 − 0.87, P-value = 0.025). CONCLUSIONS: Based on the results of the present case-control study in the Iranian population, it was concluded that PDP, which involves consuming vegetables, fruits, cereals, dairy products, and low meat consumption, reduces the odds of CRC. In conclusion, adherence to PDP is associated with a decreased odds of CRC.