DOI: 10.11648/j.sjph.20261405.13 ISSN: 2328-7950

Diet and Colorectal Cancer: A Comprehensive Systematic Review of Epidemiological Evidence

Dandonougbo Novignon, Dandonougbo Koffi, Sossou Kodjovi, Mensah Komlan, Dandonougbo Tossavi, Tabago Dissirama
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Colorectal cancer (CRC) ranks among the most prevalent cancers worldwide, with lifestyle factors including diet playing a crucial role in its development and progression. This systematic review aims to synthesize current epidemiological evidence on the associations between dietary factors and CRC risk, following PRISMA 2020 guidelines. A systematic literature search was conducted in PubMed/MEDLINE, Scopus, Web of Science, and Cochrane Library databases for articles published between January 2000 and December 2025. The search strategy combined terms related to colorectal cancer, dietary factors, and risk factors. Studies were included if they examined human populations, assessed dietary exposures, reported CRC outcomes, and were observational studies, interventional trials, systematic reviews, or meta-analyses. Two reviewers independently screened records, extracted data, and assessed quality using Newcastle-Ottawa Scale, Cochrane RoB 2.0, and AMSTAR-2 tools of 3,150 initially identified records, 90 studies met inclusion criteria and were included in the systematic synthesis. The reviewed evidence indicates that high consumption of red and processed meats (RR: +12-18% per 100g/day), saturated fats, ultra-processed foods, alcohol (dose-dependent), and tobacco (RR: 2-3× vs. non-smokers) is associated with increased CRC risk. Conversely, diets rich in fiber, fruits, vegetables, whole grains, fish, olive oil, dairy products, and specific micronutrients (vitamins D, B-group, C, E, selenium, zinc) show inverse associations with CRC risk (20-50% risk reduction). Epidemiological studies suggest that modifiable lifestyle factors may influence CRC risk by approximately 60-70%, though these estimates derive primarily from observational data with moderate to high heterogeneity. This systematic review highlights the potential for CRC prevention through dietary modifications. However, due to the observational nature of most available evidence, further well-designed prospective studies and randomized controlled trials are needed to establish causal relationships. The findings should be interpreted as associations rather than causal effects.

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