LB107 - ASSOCIATION BETWEEN PROTEIN INTAKE AND SUBSTITUTION OF DIETARY PROTEIN SOURCES WITH COLORECTAL CANCER RISK: A LARGE CASE-CONTROL STUDY IN IRAN

LB107

ASSOCIATION BETWEEN PROTEIN INTAKE AND SUBSTITUTION OF DIETARY PROTEIN SOURCES WITH COLORECTAL CANCER RISK: A LARGE CASE-CONTROL STUDY IN IRAN

M. S. Seyyedsalehi^1,*, P. Boffetta^1,2 on behalf of On behalf of the IROPICAN Study Working Group.

¹Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy, ²Stony Brook Cancer Center, Stony Brook University, Stony Brook, NY, United States

Rationale: Colorectal cancer (CRC) is among the most common cancers worldwide, with diet recognized as a major modifiable risk factor. Although protein is an essential nutrient, its association with CRC risk remains unclear. This study aimed to examine the relationship between total dietary protein intake, protein sources, and CRC risk in a large multicenter case-control study (IROPICAN) conducted in Iran. Additionally, we evaluated the impact of substituting dietary protein sources with other macronutrients on CRC risk.

Methods: We analyzed data from 833 CRC cases and 3,158 controls. Dietary and lifestyle information were collected using validated questionnaires. Protein intake was categorized into tertiles. Multivariate logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for energy intake and potential confounders. Substitution modeling was applied to evaluate the effect of replacing one macronutrient or protein source with another. We thank the DARE – DigitAl lifelong pRevEntion project for supporting this work.

Results: Higher total protein intake was associated with increased CRC risk (OR = 1.13, 95% CI: 1.09–1.16), as was intake of protein from animal sources (OR = 1.12, 95% CI: 1.09–1.15). Conversely, higher intake of plant protein was inversely associated with CRC risk (OR = 0.89, 95% CI: 0.84–0.95), particularly for colon cancer. Substitution analyses suggested that replacing carbohydrates, fats, or animal proteins with plant proteins could reduce CRC risk. The protective effect of high plant protein intake was more evident in individuals with normal weight, medium socioeconomic status, males, and those over 50 years old.

Conclusion: Total and animal protein intake were positively associated with CRC risk, while higher plant protein intake appeared protective, especially against colon cancer. These findings highlight the importance of protein sources in CRC etiology. Promoting plant-based protein sources — such as legumes, nuts, seeds, and whole grains — over animal proteins, especially red and processed meats, may play a significant role in CRC prevention. Future research with well-designed prospective studies and randomized trials is warranted to further validate these associations and inform dietary recommendations for cancer prevention.

Disclosure of Interest: None declared